How do self-adjusting hydraulic disc brakes work? I have Avid Elixir brakes on my mountain bike.  They are the only part of the bike that's a total black box to me.  I understand the principle behind disc brakes, and I understand the principle behind hydraulics.  I could draw a diagram of how this all goes together.  That said, I've been told that they automatically adjust for wear on the pads, so as the pads wear down, the braking action is the same.  Part 1 of the question: Is this true?  Part 2: How the heck does it work?

I think the answer he was looking for was how they adjust as the pads get worn.  There is a check valve in the master cylinder, that will allow enough fluid from the reservoir when the lever is pulled.  If more fluid is needed because of pad degradation, it passes it into the active system.  Therefore with more fluid in the system, the piston is pushed out slightly more and the pad is the same distance from the rotor.

That is why your res. needs to be topped off occasionally.

Epic Bleed Solution did an amazing post explaining the details of hydraulic disc brakes, covering concepts and mechanic principles, different fluids, pads, rotors, etc. It's a very good introduction to hydraulic disc brakes that you can find here: http://www.epicbleedsolutions.com/blog/how-hydraulic-brakes-work/


Would a military helmet make a safe alternative to a bicycle helmet? I am in need of a new bicycle helmet and have been exploring some alternative options. One possibility I am considering is visiting my local Army Surplus store and getting a helmet there. I only use my bike for commuting, 3-4 miles in a single trip, tops. So the weight or lack of ventilation won't be a problem for me. Additionally, having a helmet durable enough to not need replacing after a minor bump or contact with the ground seems appealing (and cost-effective).
Right now, I am thinking something along the lines of a vintage WWII helmet.

So my question is would this be a viable and safe option for me or do I need some sense slapped in to me? I figure if it's meant to deflect bullets or shrapnel, then it should work fine for a fall or if I get hit by a car.

Obviously, I'll have look into the legality of this for my state on my own. But I am wondering if anyone out there has any experience or advice for me on this topic.

Thanks.

Bicycle helmets contain crushable foam that works to extend the duration of impact by about 6 ms (milliseconds).   This doesn't make the impact force disappear, instead it extends the duration of force experienced by the brain.  By extending the duration, you reduce the peak force.  The brain can withstand impacts to some degree, however if the impact is too forceful over too short a period of time (like your head hitting asphalt), the peak force experienced by your brain becomes too high resulting in brain damage or even death.  While 6 ms may seem  small, it can be enough to reduce the peak force experience from lethal and/or damaging to survivable and/or reduced damage (see Figure 1).

A)  B)
Figure 1.  Impact force by time a brain sees with a helmet (A) and without a helmet (B).  The total energy is the same (area under the curve), but the peak force is lower for the brain with a helmet.  (Source: http://www.bhsi.org/)

Modern military helmet are designed to protect against things like shrapnel, not absorb impacts (although newer research may change that).  As a result your peak impact force in a crash will not substantially change and you will be under a similar risk for brain injury as being helmet less.

Also you mentioned having to replace bike helmets that take an impact as a downside. If you wonder why bicycle helmets are not made with foam that "bounces back" (e.g. hockey helmets) this is because it can cause more damage in an impact.  With this type of foam your brain receives force in the initial hit and then it experiences a secondary "hit" as the foam returns (often these non-crushable foams return rapidly).  Crushable foam however does not rebound as it remains crushed. The downside is that once it is crushed it no longer provides any protective benefit and needs to be replaced. By extension when the crushable foam degrades it also needs to be replaced.  This is why it is also suggested that old bicycle helmets also need to be replaced (what constitutes old is up for debate).  In this case the crushable foam has degraded over time and its impact absorption properties change for the worse and will not provide the same benefit in an impact as a newer helmet with foam that has not degraded.

Finally, I do remember hearing about a new type of foam that behaves similar to the crushable foam used in helmets, but rebounds slowly.  I will have to work to find that reference. But if they are in the marketplace they will be more robust to hits and repeat impacts.

Old WWII helmets were basically the original motorcycle helmet.  You might want to consider a newer military helmet if you got one, look fort the Kevlar helmets as they are designed to absorb the impact of small rounds and I know 9 mm rounds produce 467 joules of energy on impact and is designed to penetrate, a helmet actually has to be stronger to stop small objects from penetrating it because the impact is in a smaller and more localized area on the helmet's surface than if it were to be dropped or be on the wearer's head when they fell.  This whole logic that 'it's designed to protect against sharp objects but not impacts' is kind of flawed.  Modern military helmets have adjustable foam pads inside and exceed DOT standards for even a motorcycle helmet when looking at the numbers.  The main reason most people don't use military helmets on motorcycles, except for military personnel, is because the modern helmet is what you'd want and it's expensive.  military helmets have been being designed to take blows from blunt objects, sharp objects, and falls for years and have evolved since the first helmets were worn into battle over 3,000 years ago.  They normally have a space around the head and a padding inside to absorb impacts and have been designed that way for over 1,000 years.  They are really your best choice of helmet for pretty much anything since they are tested more rigorously and have to protect a soldiers head in the event of a fall, something falling on their head, and more. They're just expensive, soldiers only tend to use them on bicycles and motorcycles because they are issued to them and therefore it's cheaper for them, most other people use motorcycle helmets or bicycle helmets because they're considerably cheaper than military helmets.


getting the crank arms off an old bsa bike So I'm resuming work on restoring a bsa bike for my sister.

The first thing I need to do is strip it as it's in need a of new paint job.

I'm having trouble removing the crank arms.

They appear to be bolted on using a round headed bolt then a nut on the other side.

Is there something am doing wrong because the bolt doesn't appear to come out. Even when I whacked it multiple times with my hammer it still didn't budge.

Use a length of conduit or other metal pipe or some other kind of brace to transmit load from the crank to the ground, so that the hammer impacts are not going right into the bearings. Then hammer it with everything you've got. Try to go for fewer strikes and more power. It's a press fit you're overcoming; it's supposed to be stuck.

Always plan on having to replace the cotters. They don't necessarily get too mangled or bent to re-use but they often do. Replacements are still pretty available, although there are multiple diameters (I think 4). You re-establish the press fit with a hammer or press, never via the nut - it can shear the cotter if you try. Sometimes you have to file new cotters to make the angle right (make the cranks 180 degrees apart) if you only replace one of them. The other very important thing is to re-tighten the nut on a freshly installed cotter after a break in period at first, say 50 miles.

Despite being a pain, they do work and all you really need to work on them is a hammer and piece of pipe.

Check out Sheldon Brown's page on this topic


When is a child ready to switch from scooting to pedaling? Last year, we bought a child-sized bike and removed the pedals. My three-year-old has been using it as a push bike (a.k.a. balance bike, run bike, or scooter) and learning how to balance. The plan is that once she's ready, I'll put the pedals back on, but I won't be adding training wheels. However, I don't want to put the pedals back on before she's really ready because it would be a pain to take them back off again.

She's now at the point where she can coast for about five seconds at a time, but she doesn't ride in a particularly straight line. She often asks for pedals, though I'm sure she doesn't appreciate the effort that will be required.

How do I know when she's ready and it's time to put the pedals back on the bike? What specific goal can I give her to work towards (i.e., "When you can do XYZ, then you can have pedals")?

Related question: What is the best method to teach a young child to ride?

I did the same thing for my son when he was 2. After a year and a half, he just "looked" ready. I knew he could ride so I had him try pedaling. I have a short hill in the front yard and put him near the bottom. He was determined to NOT ride properly, so after about 25 feet he "fell" off and said "SEE!! I can't do it!" I laughed and said, "You did it almost all the way across the yard!" Just then his mom came out and asked him to show her, and he jumped up and rode for a few minuets all by himself.

I made sure that the seat was set so that he could easily touch the ground with both feet at the same time so that if he got nervous he could just stand up, but it never got to that point. He was 3.5 years and my girl was 3.75 years when they both learned to ride (I was a few weeks short of being 8 when I learned)

I don't think there is any magic rule to guide yourself with, just look at her confidence and let that be your guide. Make sure she can touch both feet on the ground at the same time, and it really shouldn't be much different than what she is doing now.

(PS: If you do put the cranks on and she just can not do it, you can always just take the pedals off rather than the whole crank set, that will save a lot of time!)

You can see the video of him a few months after he learned to ride at youtube here: http://youtube.com/watch?v=fnb7uhC1J2Q

A few months BEFORE he learned to ride: http://youtube.com/watch?v=jfrz0Q6I_rw

at age 8 when he learned a "Nothing": http://youtube.com/watch?v=CdOfmWYt9FQ

My girl when she learned: http://youtube.com/watch?v=vP6qio6LS78

At the age of 4 or more, when the child is confident with keeping balance on a 2 wheel scooter like this


Is it safe to cut off from the inside of my helmet? Having a rather "pointy" head (think of something like Patrick Stewart's head), all bicycle helmets I've every tried on tend to have contact with only one point at the top of my head.

Now my idea was to cut a little bit away from that rigid foam at that location. Let's say 1-2 millimeters at the size of a dime.

My local bike dealer told me that the whole helmet has a fine-tuned structure that completely breaks down when removing even the slightest piece of rigid foam, no matter how small.

While this sounds strange to me, I'm confused right now.

Therefore my question is:

Does a bicycle helmet still has protection when slicing some 1-2 mm from the inner rigid foam at a size of a 1-2 cm circle?

(I'm from Germany, in case this matters; maybe our helmets here are different)

Unbeknownst to many consumers, different helmet manufacturers use different molds for their helmets. Just like some shoe brands are known to be thinner or wider than other brands, some helmets are more oval, some more round, and some pointier. Even from the same manufacturer, their racing models might be different from MTB, skateboarding type, and general lines. And there might be a helmet with a vent hole in exactly the right place out there.

It's important to find a helmet that fits correctly and comfortable. It might take having to go to different stores and trying different brands and types (or even to a store in a different country, if you have the opportunity).

That being said, through, if it were my head and I had to decide between a helmet that was partially shaved to fit -- or a larger helmet with some extra padding to fit; I would choose the latter. The helmet manufacturers provide extra padding pads of varying thickness in the box because they know they can't produce a helmet that fits perfectly on everyone's head. As long as the helmet is snug on your head and not uncomfortable, you should be good to go. Remember that many cyclists wear beanies in the winter and cycling caps in the summer under their helmets -- something that is well known to the helmet manufacturers.

Remember the worst helmet is the helmet you don't wear.

They are designed to make money ..

ESP helmets do nothing to protect from concussion .

They are safer the more you add fault lines .. so they can crack at lower stress levels .

As tested they only absorb motion after 200 plus G s ... while 50 plus G's while cause CONCUSSIONS.

Dealers will try and scare you into buying a replacement if yours has a fingernail scratch inside...

Yet a few knife slices will actually lower your chances of concussion..

See David Camarillo TED.COM talk on why helmets don't work .


Aluminium rigid fork for winter I'm looking for the bike for winter riding and found this one.

It's all good, except for the fork: some people say that aluminum rigid forks can not absorb vibration and therefore are bad for the winter 'cause there's firm snow and ice, which is not smooth at all.

So, are they right and I have to look for steel or carbon fork? (I'd really like to use rigid one for the winter)

Presumably you are looking for a cheap bike to ride in harsh winter conditions. The advertised price of 35,960₽ is about US $615 (at the time the question was asked) which would be considered a quite inexpensive bike here.

Your choice or tires is going to make a much bigger difference than a carbon fiber vs aluminum fork. An aluminium fork will be fine, but look for a bike with clearance for bigger tires.

Aluminum has about 1/3 the modulus of steel , so will elastically strain 3 X more with the same load. I don't know if that makes a difference for absorbing shock on a bicycle. And aluminum also has 1/3 the strength of steel ( depending on heat treatments) so will plastically deform ( fail ) at 1/3 the load of steel. Proper painting the steel will essentially eliminate rust in these mild conditions.  Wiping with an oily rag will also greatly reduce rust on bare steel. Bare steel bridges, etc , are normally "weathering "steels ;containing small amounts of P , Cu, Cr , etc .


Fat bikes and pannier racks I'm trying to research fat bikes for rack attachment holes and have not seen any so far. I'm a long term commuter and must have a way of attaching my panniers to my bike. Backpacks are out because I'm a pack rat, plus I do my shopping with my bicycle and that won't work. I believe I saw one commuter with a rack that connected to his bike by attaching just above the wheel openings, but couldn't find a name on it to do some research. Can anyone offer some help? Thanks.

Many of the expedition/endurance race fat bikes will come with rack mounts.  If you plan on "packratting" and carrying groceries, you should avoid the seatpost only options.  They generally have low weight restrictions and can also have issues with the bags flopping into your wheels (they are often missing the side panels regular pannier racks have).

If you look around a bit more, it should be fairly easy to find fat bike companies making rigs that are rack ready.  At most of the winter endurance races, racks and sometimes panniers are common.  The Surly Pugsley (the original production fatbike) still comes with rack mounts (rear AND front).


What should I factor in when moving from a 50/34T to a 53/39T I have a 11-32 cassette.

I'll be looking to do this for short 30km rides and long 100km rides on the weekend. the 30km rides have a few hills, nothing major, whilst the longer ride is generally quite flat.

Other than changing the chain to compensate for wear as well as factoring in the larger diameter of the new crank what else should i consider?

Apologies, I am very new to cycling and not sure where else to ask or where to look for information.

Changing from a 34 to a 39 chainring is roughly the same as changing from a 32 to a 28 max rear sprocket.  In other words, you'd lose your lowest gear.

You don't say what the motivation for the swap is.  Do you find 50-11 not high enough?  Swapping to 53/39 should work fine, probably without any change of chain.  You only need another 3/4 link, so you might need one more.  50/11 is quite high already, so many would suggest you just need to learn to spin faster. As others have said, you lose your current lowest gear.  Do you use it now?  If a compact is not cool, a 53/39 will solve that problem.


Why do my pedals shake and pop? I just purchased a cruiser bike online that I had to assemble.

When I rode it for the first time, I notice my pedals felt shaky, whether pedaling or coasting, and when I did pedal every few seconds they made a crack/pop.  I don't feel anything abnormal when this happens.

Turned the bike over, and I noticed the chain shakes too. It is tight, but the wheel looks as if it is up as far as it can go- it looks like if I adjusted it further to loosen the chain, I'd be at risk of it falling off.

I opened up the wheel sprocket- no broken ball bearings

Does any one know why this is happening, and if its an easy fix or defective bike that I need to return?

The popping sound could be coming from the chain not lineing up properly on the freewheel. This can happen if the chain is either bent and or twisted or if the chain is not the proper size for the sprocket. More than likely it is a bend or twist in the chain.

They are flexing too much. You may need to make a pedal upgrade. Also, your chain is clearly too long if your wheel will fall off if you try to slide back your tire. You should probably take about 3 links out of the chain then the bike should run fine.


My back brakes don't lock the wheel (skid): feature or a bug? When I apply rear brakes only (I know this isn't the proper way to stop), it slows me down but never locks the wheel to the point of skidding (on dry pavement anyway). This is a new 'cyclocross' style bike with disc brakes. It has both regular road bike levers and auxiliary brake levers, if that matters. I am exerting quite a bit of force on the lever and they do not touch the handlebars (bottom out). It seems like a defect to me because that's not what I'm used to from my old hybrid bike with V-brakes, but having had it in the shop a couple of times, I'm starting to wonder -- are these brakes ineffective or is this a design feature to prevent skidding?

If this is a flaw, what is wrong - the brakes, the pads, the cables/adjustment or something else?

If it's a feature, how does it work?

Disc brakes should be capable of locking the rear wheel.

If this is a new bike I would suggest it's a set up/ breaking in issue rather than a fault.

I'm not sure of the brakes you are running, but guessing they're cable discs due to having axillary levers. I'd ensure :

the brake pads are bedded in
the disc brake rotor alignment is good
the pad contact point is correct (refer to your brakes manual)

Check out this question, Disc brake break-in?

If that didn't help I'd check that the auxiliary levers aren't impeding the full cable pull.

Just tighten the cable, they just loosen up over time and they don't pull on the brake as well.


How does a bike's weight affect the overall experience of owning it? Naturally, carrying a light bike up the stairs is much more enjoyable compared to a heavier bike. Are there any other aspects of a bike which are affected by its weight?

For example, would the weight affect handling at low speeds? Higher speeds? Turning? Stability in strong crosswinds, heavy rain or other adverse weather conditions?

What does the weight say about a modern bike's components? About its durability or dependability? Maintenance? Wear and tear?

Are lighter bikes always better? What would be a reasonable weight threshold below which gains are diminishing?

As an inexperienced cyclist looking for a new bike, I'm unsure how much I should be paying attention to its weight.

UPDATE: what specific weight ranges should I be looking for these days? What would be considered very heavy, reasonable, and at what weight do we enter the multi-thousand-dollar pro racing bikes?

I found a cheap made-in-China fixie in Singapore (where I live); when I learned it weighs 17kg I realized why it's so cheap!

Other than the obvious fact that your better quality (and better handling) bikes tend to be lighter, there's no real correlation between weight and performance (other than a modest effect on acceleration and the obvious effect on hill climbing).

But you can generally (with some exceptions) assume that a bike that is quite a bit (like 2x) heavier than others of the same basic style is poorly made, with poorer quality components.  Eg, hubs and rims are apt to be stamped steel rather than machined aluminum, the crank is likely a solid steel one (with large, crude bearings) vs a 3-piece one with alloy arms and better quality bearings.  The spokes are probably just plated steel rather than stainless.  The pedals are probably stamped steel, and when you spin them you can hear the bearings rattle.  And the tubes in the frame will be so thick and heavy that the bike will feel stiff and "dead".

That said, there's no need for a beginning cyclist to find the lightest possible bike.  Eg, a good quality steel frame will be maybe five pounds heavier than the equivalent aluminum one, but the steel frame will be cheaper and more durable.  Other components may be heaver or lighter as well, making possibly a 10-15 pound difference between two essentially identical bikes, but beyond a certain point lighter, more expensive components (eg, drilled brake levers, ultra-thin tires) are less durable than their slightly heavier counterparts.

Finally, if you're still tempted to spend an extra $300-3000 to get that ultralight bike, ask yourself how much you weigh, and whether you couldn't afford to lose a pound or two.  The heaviest thing, by far, on a bike is the rider.

What most of these answers don't take into account is that the weight difference is very noticeable because a human being powers a bicycle. For example let's look at cars and Lbs/HP, First up is a Fiat 500 2,465/100, that's 24.65 LBS/HP. Get into a 3,300 LB car that has 300 HP and that LBS/HP drops to 11 LBS/HP. The engine of a car doesn't feel the sensation of the weight difference, the human body does. So if I have a 35 LB MTB from Wal-Mart or Target, as a cyclist I can produce whatever Wattage I can regardless of bicycle. The bike shop sells a 28 LB modern MTB. Let's say I can produce 1 HP with my fitness level. There's no way I want to pedal at that much of a disadvantage in LBS/Watt or LBS/HP. That extra 7 LBS sucks carrying up a hill and it's going to suck dragging it around on flat ground too. Acceleration maintaining speed requires more effort. Just because you aren't carrying it in your arms doesn't mean the 7 LBS still is wearing you out physically. That 7 LBS is 25% of the 28 LB MTB. It's 1/5 or 20% of the 35 LB MTB. Another thing, the contact patch creates resistance too, more contact patch with the ground is going to be like a brake pad that drags against the rim. End of the day, you'll work harder and 2 cyclists of similar fitness over the course of an hour in the saddle is going to win every time.


Front V Brake squealing on Trek FX 7.4 I know this is a frequent question in this forum...  To use a cliché "I've tried A, I've tried B. what do I do now?"...
I have a very persistent squealing from my front Tektro v brake, on my 5-yrs-old Trek Fx 7.4.  I've tried:

Cleaned the rim and pads , with isopropyl alcohol, then with brake cleaning fluid
Installed new pads, twice (two different brands)
"Toed in" the brake pads, tried more or less, even no, toe-in
Checked the wheels for true and play in the wheel's bearing (both OK)

... and no luck!  Front brake still shrieks like a banshee...  It seems like there is some play on the brake caliper... however on my wife's bike (similar model), there is some play but hers doesn't shriek at all.  What is the next step?  Should I replace the front brake set?  Try baby powder on rim?  Try cleaning the rim with fine steel wool?  Thanks for any help...

Since a single pair of V brakes is not much more than 2-3x the price of decent set of pads, why won't you try a different pair of V brakes? It's not hard to install, only bit more work as changing the pads. Also having some play on the brake arms is a cause for concern -- there shouldn't be any play in decent brakes apart from sidewards play against the spring due to the pad gap.
In one of my bikes, the front brake squealed like hell. It's not V brake but cantilever. I assume some combination of cantilever brake arms, rims, fork and pads caused the squeal. Changing the Kool Stop salmon pads to Shimano S70C pads fixed the squeal for me.


How tight should a fixie's chain be? I ride an SE Lager fixed.

How tight should the chain be and what is the best way of measure it? I have a chain tug so I can be pretty accurate in dialling in the right amount of tension.

I don't like to have much slop. Part of the joy of riding fixed is having a direct connection to the road. I like to have it adjusted so that there's no significant movement of the pedals when the bike is stationary. This often equates to about a centimeter of movement in the chain if I squeeze the top and bottom of the chain mid-way between the cog and chainring but it's hard to judge how hard I should be pushing to get that movement.

As always, Sheldon Brown has a lot of information, mostly about centering the chainring(!!) and recommends having the chain as tight as possible without binding.

The simple answer is, as Sheldon brown says, as tight as possible without binding.
But define binding. The noises you described on your chain in your previous question were symptomatic of binding or of a worn chain. The description you've given there of how you run your chain tension is tighter than I would recommend.

  To clarify the tensioning - When I replaced the chain I adjusted the tension. There was a very noticeable adjustment required. But then when I subsequently adjusted the rear cog I didn't adjust the tug from it's setting with the new chain. I agree that I might have changed the tension marginally just be removing and refitting the wheel.

1 millimeter of movement is too tight, in every case I've seen. The manufacturing tolerances on the components (cog, chain, and chain ring, ans well as the hub, and BB axle), would need absolute perfection to allow that tight of tension to function without damage or noise. I've never seen good enough all at once, and you would need to be amazingly lucky or diligent to find that mix of perfection.

Typical tension on a fixie or single speed is roughly 1/4" to 1/2", or 5-10 millimeters, when pressing on the chain from the top, and from one side. A single speed requires slightly less tension, because the bearings in the freewheel will bind, and it won't roll at all, where a fixie will just be noisy and prone to wear. Make sure you check for the spot where the chain is tightest, and do the adjustment there, as well.

You don't need to be that tight, and your drive train will still maintain good contact between pedal and wheel.

I probably run my chain tighter than I should but a measurable flex of 1 to 2 cm should be okay.


1986 Stumpjumper Sport Cog Replacement Original Shimano Deore components all around.  Shimano MF Z012 5-cog freewheel.  Biggest cog is 30 teeth is worn out, chain skips,  and that cog needs to be replaced. Rest of cogs are ok.  Are compatible individual 30 teeth cogs still available as new parts?  Source?  If not, what's the recommended solution?

If the 30 is worn to the point its slipping and jumping, I would my guess the others must be due for replacement, along with the chain.

Individual cogs tend to only be available in high quality gear, so a new cluster will probably cost less than a single cog.

Replace the cluster and chain if you can afford it. If not, the cheapest way would be to get a beater from the tip, side of road etc, and take the 30/32 off that. Its rare that the largest cogs are worn out more than the others  (more teeth per rotation, lower torque) so even a really old bike is likely to have a useable large cog.

Agree with other answers on replace the freewheel and chain.

You should also look at the chain ring(s).  Replace if worn.

If you are wearing out the biggest gear then you are spending the most time in that gear.

You may want adjust the range like 14-32.

If you replace the front chain ring then maybe a little smaller to put you more in the middle of the freewheel for your most common gear.  This gives you room up and down from your most common gear.

If you are running the larger front chain ring and wearing out the 30T then spend more time in the smaller front chain ring.


Bike doesn't brake immediately and comes to a squeaking stop. Do I need to get new brake pads? I was given a bike by a friend (for free) and have taken advantage of biking over short distances to work and school.

When riding I noticed that the braking is not immediate when I applied the brakes and the bike comes to a squeaking stop.

The bike has rim brakes. The brake pads seems to be quite stiff and don't appear to be worn out very much. I am still trying to diagnose what is affecting the braking. Do I need better quality brake pads? Or do I need to adjust the pads and the levers on the wheels get the bike to stop better?

You may need to replace the brake pads, and the brake calipers and levers are very probably out of proper adjustment.

As this is a safety issue, you should definitely have the brakes examined and adjusted by a bicycle repair mechanic.

If you feel confident about making adjustments yourself, and have the necessary tools, there are a number of good resources that will show you how to accomplish the task properly. My favorite is the Park Tool Company YouTube Channel. They have a specific set of videos that deal with rim brake adjustment, including identifying the brake caliper types with links to the appropriate adjustment video.

If the pads are heavily worn, or have hardened due to age you should replace them - pads are reasonably cheap. If braking is still not strong enough after making adjustments then you could consider getting a set of more expensive higher performance pads.

Try to rotate your wheel by hand while pressing brakes. Left hand holds brakes and right hand presses tire down with power of your weight. It wheel rotates quite easily, you need to fix brakes. Firsr chexk the same focus on another wheel. If it has same problem, try new brakes. If not, there can be a problem with your pads and rotor (they can be oiled a bit). I suggest replacing both pads and rotor at one time in case of oiling.
Anither problem can be overheated pads. Some pads get baked and they become very hard and too slick. Try using new (clean a rotor before it with some kind of de-oiler)


Is it better to get a commuter bike with a front suspension or without one? Is a commuter/city bike without front suspension comfortable?

Commuter or city bikes are designed for paved surfaces. A suspension fork on such a bike is not going to add much comfort, except perhaps when riding over potholes or kerbs, which are avoidable.

Suspension forks add weight, which brings a different type of discomfort as you have to exert effort to move that weight around.

This gets worse the more inexpensive the bicycle is. Low end suspension forks are heavy and have poor performance.

I live in Fort Worth, Texas, and I find that a suspension fork works well for my commuter bike.
My morning commute finds me riding on roads where there are: no bike lanes, bad roads, distracted drivers, or drivers in a hurry to get home for their morning sex. There are times on the commute I am forced to quickly ride off road in order to avoid that aforementioned bad drivers. "Suspension fork is good," I say to myself.
Halfway to work I eventually reach an upper - income area where there are some bike lanes,   and connected streets that lead me to work. Also, at five a.m. most of the homeowners in this residential area are still asleep, so the dangerous drivers are still in bed.
The suspension fork does help because I am not forced to stop and wait until the bad drivers have gone away.


Custom/modified Drivetrain 2x/3x Considerations and Planning Planning a drivetrain setup for a new bike:
Currently running old Shimano 3x9 44/32/22t on 11-34t, which gives me 19-115 gear-inches (about 620%).
I used 29x2.0, 170mm crank to calculate my current setup at https://sheldonbrown.com/gear-calc.html.
The old 3x9 provides me with nice little jumps between the gears, which is something I definitely do not want to miss.
Turned out to be not too easy to find something nearly close the gear setup of my 12 year old bike...
Requirements:
I definitely want the option to mount a set of 29x3.0" tires, which may already cancel out 3x cranksets (even though full boost is used?). And I want to stay in the sub-20 and 110+ gear-inch range, preferably even going a bit lower than 18 gear-inches.
Also I do not want to use drop bars/road-shift-levers. The ideal rear-levers would have gear-indicators, but only found some Shimano/Sunrace-SRAM variants for 11speed.
Added current frame considerations:

Surly ECR 29+ (Large)
Jones Steel Plus LWB Diamond (Large)
I know that at least the ECR is good with 2x and 29x3.0" tires. Both support 148mm boost.

Seems like 2x still allows for comparable small steps, while having the extended 600%+ range.
SRAM/Shimano 2x11 of either brands uses 11-*t cassettes, which ends up in a significantly lower max-speed with the corresponding dual chainring cranksets.
The only off-the-shelf option getting close, seems to be the Shimano M9100 XTR 2x12 (10-45t,38/28t). And to some extend, the 2x12 XT/SLX (10-45t,36/26t) drivetrains. But those further decrease the higher gear-inch range (of course, providing better climbing gears instead)
I was thinking of going with XTR M9100 and maybe try to fit a 26t granny, when derailleurs are working fine with it.
But the full M9100 XTR setup is pretty expensive, also in replacement parts...
What are your experiences with custom or modified dual chainring cranksets, maybe even as far as 15-20t difference (e.g. 40/20t)? It should allow for using the cheaper 11-34 or 11-36 cassettes. I guess, I wouldn't even have to go 12-speed that way.
Which combination of manufacturers/models/series of cranksets, cassettes, front/rear derailleurs and matching shift levers did you came up with to make it work?
Hoping for an interesting exchange of known-good custom drivetrain setups. Maybe someone has additional ideas, which I failed to consider yet?
Best Regards,
Wiener :)

In my reading of your question, the big limiting factor is the 29x3. Your question isn't just about what FD/chainring jump hacks function and how well, but also of those which will also work with your clearance needs. The answer to that question is generally not very many, but it's going to depend on the chainstay length of the frame in question, whether the cranks are boost, etc.
Contemporary double MTB FDs of the dainty, short variety that are made to give as much clearance as possible do not play nice with hacking the jump that much. I don't have a ton of experience doing it, which admittedly is what your question is driving at, but if you look at one you'll see that their total top-to-bottom cage space is limited and the contact points for the chain are not large. Maybe you can get it to function okay with 2t extra jump, maybe not.
What always works is just going with a larger cassette range than the total capacity of the RD can handle and accept having a slack chain in some small-small gears. This has been the standby approach to cheating the range on derailleur systems forever and it applies here just the same. Then you're not forever playing games trying to make a front derailleur make a shift it wasn't designed to.
Don't discount just going Rohloff. At 526% the range isn't quite what you're looking for, but obliterating all clearance problems forever is huge.

I use a modified 26/36/48 crankset on my touring bike. I removed the 26t chainring, as I do not have a use for it. I would ideally pick a 11-32 8-speed cassette, but with the 47cm chainstays a 32-tooth rear and 48-tooth front setup would mean 116-link chain is not long enough. Chains only little longer than 116 links are not available from Shimano (you have to buy 138 link chain then at considerably greater expense than 116 link chain), so I have to accept a 11-30 8-speed cassette. Of course some other chain manufacturer could perhaps sell 118 link chains, but then I cannot use the superior reinforced connecting pin system of Shimano and have to use the horrible quick links that are impossible to disconnect without pliers if the chain is full of dirty sandy oil mixture. Furthermore, having to carry few quick links would mean more extra weight for my emergency tool kit when compared to carrying few reinforced connecting pins, and a portable mini chain tool is necessary anyway. The reinforced connecting pins are also much cheaper than the quick links.
The crankset is actually intended for 9 speeds (it's a Deore Hollowtech II crankset and those are hard to find for 8 speed setups -- I wanted the Hollowtech II feature because the bottom bracket has durable bearings and durable spindle at the same time, being of the outboard type). The rear derailleur is also intended for 9 speeds (it's some old Deore XT). Both of these work just fine in the 8-speed drivetrain. The shift levers are Ultegra 8-speed bar-end shifters. I don't remember what front derailleur I use other than it's intended for double chainring setups. Anyway, the front shifter is of the friction type so the shifter works with all cable pull ratios. Besides, a double front friction shifter is essentially equal to an indexed shifter because the limit stop screws constrain its movement, while at the same time allowing trimming which an indexed shifter system would not allow.
I find that the 36t/30t low gear gets me just fine up very steep hills if I ever encounter one -- most of the time I don't and thus don't need to use the loweest gear I have. At the same time, 48t/17t and 48t/15t allow leisurely flatlands cruising and 48t/13t allows high speeds when I need them. The 48t/11t gear is unused, but if I had the option to switch the 11-30 tooth cassette to 13-30 tooth I wouldn't as I prefer large jumps between gears so that a large change in gear ratio is felt when I operate the shift lever. The 11-30 tooth 8-speed cassette has 15.41% jumps between gears and a hypothetical 13-30 tooth 8-speed cassette would only have 12.69% jumps.
As an added feature, I installed the drivetrain with a full plastic chainguard allowing me to have non-oily trousers after riding the bike, without having to put the end of the right trouser leg inside my sock.
Recently, I have been using an e-road-bike more than the touring bike. The e-road-bike unfortunately has 10-speed drivetrain, but fortunately, the cassette is 11-34 tooth so it still has 13.36% jumps which I can tolerate although I would prefer larger jumps. The drivetrain setup in the e-road-bike is stock as I have not modified it. It doesn't seem to be feasible to install a full chainguard to the e-road-bike so I have to do without.
My preference for lower speeds is caused by lower expense of wearing parts and the observation that it's easier to have big jumps between gears by a lower speed count in the drivetrain. I am aware of a study that found that the higher speed chains are counterintuitively more durable than the lower speed chains due to improved materials despite their narrowness, but my understanding is that the increased durability of these new chains does not offset their higher cost.


Carrying Pizza on a Bicycle I have a rear rack.

However, I don't really have a good way to carry pizza.

Cables?  Any big enough bags?  I can avoid leaning too much, I'll slow on the turns if I have to..

Edit: Delivery?  Not in this town.  I just want a pizza...

For the ultimate in pizza carrying, you want a pneumatic air suspension, pendulum-based anti-sway bar equipped carrier. This are/were used by ramen delivery bicylists in Japan, although they are getting rarer (people don't order delivery ramen noodles like they used to) and mostly on motorcycles now:

With one of these babies, your pizza (or ramen) will not sway from side to side, bump around, and end up all mashed into one big congealed mess.

Of course, it costs around $400 and you can only get it in Japan. But if you're serious about your pizza carrying, it's the only way to go.

For drop bars it's as trivial as this:

(as long as pizza box is smaller than your handlebars).

Plastic bag with pizza box is hanged on hoods, and the bottom is supported by shifter cables. If you don't have a plastic bag around your pizza you can hold it with your hands.

You may somehow adapt the method for bullhorns and time trial bars. For flat bars you can hang the plastic bag straps on bars and put the rest on the stem.

EDIT: Yes, this method isn't the safest for you and pizza if you want to employ it on regular basis. But it makes perfect sense for me as an ad hoc way to carry a pie from the nearest pizzeria. I only tested it on 5-minute ride with cheap thick-crust pizza, and it was in perfect condition when I opened the box.


Can I use a 9-speed shifter with a 8-speed cassette? I'm looking into replacing shifters on my MTB. Currently I have 8-speed Shimano Alivio shifters - will 9-speed Deore or SLX shifters work? I do not care if one of the shifter's position will be unreachable.

Later I may replace the cassette to 9 speed to, but I do not want to do this right now.

Unfortunately you cannot do that. The COGSET and the SHIFTER must have the same "distance", or more correctly, the same lateral distance (on the pulley) for each lenght of cable pulled (on the shifter).

When you go from 7 to 8 speed, the distance between cogs is the same (because the freehub shell is longer), so you could use a 7 shifter with an 8 cogset and one gear would be unreachable;

But when you go from 8 to 9 speed on the shifter, the expected distance between cogs change (because the freehub shell for 8, 9 and 10 speed is the same). Then you need a 9 speed cogset too, so that EACH shift will correspond to the CORRECT DISTANCE of lateral movement in the derailer.

If you move from 9 to 10, the same problem happens. That's a perverse kind of programmed obsolescence, in my opinion, since even cranksets end up being incompatible due to the chain being narrower and narrower... (look for the Sheldon Brown "Nanodrive" system).

So the bottomline is: if you want to replace shifters, you'll have to replace the cogset, and probably the chain and cranks. I would not advise you to do so only for the sake of shifter change. Consider doing it only as a last resouce.

(I for one never changed to the 9+ speeds framework. I have 5 bikes in current use, all of them with the "7/8 speed framework", and I can easily find spare parts like cogs. My 7 speed shifter (a very old Alivio) still works fine, and it seems to me it is very rare for the shifter to have a poor working only because it got old).

It will totally work.

I broke my cassette on one of my bikes, then I replaced it with Shimano Megarange 18-34T.
My command is 8 speed and the cassette is 7. As I adjusted the tension of the wire it still runs quite nice. Gear 7 and 8 on the command are representing 7 on the cassette. SO YES IT DOES WORK.

Just read this, and 7 speed and 8 speed are normally compatible anyway as they don't have any difference in spacings. So the only evidence of this working would be using 9,10,11 or 12 speeds in conjunction with an 7,8,9 etc shifter.


Repair service specifically for bike commuters? I'm not sure if this question is suitable for this site, Startups SE or neither, but here it goes: Is there already any sort of business model catering to bike commuters for expedited repair issues? If not, why not?-- is this not a viable business model?

Background and motivation

Where I live, if something happens to my bike and I need it repaired, the waiting time for it to get repaired is a minimum two weeks any time of the year there isn't 90% chance of precipitation and/or below-freezing temperatures. However, for people who use their bike as a means of commuting, this is obviously problematic. Moreover, if I tell people at the bike shops: "I need my bike to get to work [e.g. tomorrow, on Monday, etc.]" they basically don't care†: To their bottom line, there is no difference between someone who has their bike in the cellar 10 out of 12 months a year and has to get it repaired and someone who cycles 365 days a year.

Alternative solutions

Since there is no way for me to throw money at my problem (see motivation above), when I have a serious problem with my bike on a weekday, I basically cancel everything I have planned for the evening, buy the required parts right now because all places in the city which sell bike parts are going to close soon, and then spend the evening at home frantically trying to get the bike working in a ham-fisted manner with the help of YouTube videos since I've never had to deal with this problem before.

Although this method of "solving" my problem does force me to learn things about my bike and exercises my creativeness, as you may have guessed through my language, it is not a pleasant experience.

Conclusion

I know for a fact that I am not the only person who commutes daily by bike and the other commuters I know in fact do all the work on their bikes by themselves at home. Excepting those people who actually enjoy doing this work themselves, I imagine there is a huge market niche which is not being exploited... so why isn't it? Am I the only human being alive who likes riding bikes every single day but hates working on them and has the financial means to pay someone else to fix them?

† Perhaps the employee talking to me in fact does care, but since he can't do anything to make me wait less than two weeks, the business itself (referred to with the magical "they") has proven that it in fact doesn't care. This is the same with every single shop in this country. The only difference elsewhere might be that, in bigger cities, you might have a chance of finding a shop which doesn't have quite as long a wait.

You don't need such a repair service.  There is a different, more practical solution: a loan bike.

In The Netherlands, most bicycles are used by commuters, so expediting wouldn't work.  However, there are also many places that rent bicycles.  A good bike shop can simply have a couple of dozen bicycles on hand that they then loan out to a (regular) customer, so that they can still go to work, school, social outings, etc..

This is already common practice in The Netherlands.  I believe there exist car garages that do the same, so I don't see why it would be any different for bicycles.

If the bike shop is unwilling to loan you a bike, and you have the money, you can just rent a bike to cover the period you won't have access to your own.  If it happens frequently, you can buy a secondary bicycle for the same purpose.


Why are disc brakes rare on road bikes? (circa 2010) Window shopping for road bikes, I can't see many that have disc brakes. What are the reasons for this?

2016 Update

Disc brakes are now common on road bikes, even racing road bikes in the professional peloton. Most of the major bike manufacturers offer disc and non-disc options for most of their bike models. Some "endurance", "adventure", and "cyclocross" (drop bar bikes sold under "road" category, but intended for some off-road use) models only offer options with disc brakes now.

However, there is some opposition to their use in certain types of road racing. If a rider's leg contacts a disc rotor while the bike is going fast, that rotor will likely cause a serious injury (it's spinning fast and pretty thin, so cuts flesh easily).

The advantages of disc brakes are primarily in wet and/or muddy conditions. In dry conditions, a good rim brake can lock both wheels up just as well as a disc brake. So for road-racing under dry conditions, there's no real advantage to disc brakes, and appears to be some disadvantages.

Many of the "racer" style road bikes follow what's allowed for professional road bike racing, so it's possible that the current opposition to disc brakes in professional road racing will eventually lead to them becoming less popular on road bikes.

Personally, my next new bike will definitely have disc brakes. I don't race in a peloton, I do sometimes ride in the wet, and it's much cheaper to replace a rotor than to replace a rim or wheel. (rim brakes eventually wear down the rim and make you replace it)

Original answer

I think it mostly comes down to one primary thing: disc brakes weigh more and road bikes are supposed to be light.  Also, you need a heavier wheel and heavier fork to handle the forces of disc braking, which compounds the weight.

Additionally, the advantages to disc brakes (working better in mud/dirt, easier to work with a suspension, work with really wide tires) generally don't apply to road bikes or aren't what the road bike was designed for.  For any bike on the road the only likely advantage of disc brakes would be that they're more likely to work after you've ridden through something nasty (mud, puddle with oil on it, etc) that's deep enough to get on the rims, and you probably want to be avoiding any puddles you can't see the bottom of anyways.

Probably the final reason is simply that disc brakes (generally) cost more than rim brakes.

I have seen bikes made for the road that had disc brakes, but they're generally not the typical "go fast" road bike.  (Example: Kona Sutra)

Window shopping for road bikes, I can't see many that have disc brakes. What are the reasons for this?

Wheel strength, tire size and weight.
The modern (horrible, in my opinion) trend is to have a minimal amount of spokes in the wheels, with the front wheel laced radially. Disc brake force is transmitted through the spokes so these "modern" wheels can no longer be used. Even a 28-spoke wheel with disc brakes can cause the spoke tension to loosen if braking hard (been there, done that). So you essentially require a well-built (i.e. handbuilt, not machine built) 36-spoke wheel front and rear. While a 36-spoke wheel is the superior choice compared to a "modern" wheel, it weights minimally more and is minimally less aerodynamic, and some people get offended by the high number of spokes. Also a radial lacing cannot be used with disc brakes. Furthermore, even though every gram saved is worth $10 (for rotating mass $20), the value of a hand-built wheel in the minds of a typical consumer is $0, so all we have is machine-built wheels. They do not withstand the braking forces of disc brakes for a heavy and strong rider.
Also, the modern trend is to use 23mm tires front and rear for road bikes. Someone mounting even a 28mm tire or a 32mm tire (oh the horror!) is BLASPHEMY and must be prevented. A handy way to prevent that is to install brakes that prevent anything more than 23mm as the tire size (except if someone doesn't care about ample tire clearance, a 25mm tire might fit). Disc brakes do not have this prevention mechanism, so they are unacceptable.
Furthermore, a rim brake uses the rim as the brake disc. A disc brake requires a separate brake disc. Thus, a disc brake is heavier because it does not reuse the rim. Because weight is everything and every gram saved counts to at least $10 benefit, a disc brake is unacceptable.
However, carbon fiber is arriving to rims too and may not be ideal as the braking surface, so now we're seeing disc brake road bikes appear. The appearance of these disc brakes road bikes has now trickled down to bikes not using carbon fiber rims at all but rather aluminium rims.


Problem with Apollo Gradient clunky and missed gear changes About four months ago I decided to get back into riding. I bought an Apollo Gradient mountain bike. I know this is quite a cheap/basic bike but didn't want to spend a lot if I didn't stick with it. I have stuck with it and will eventually upgrade to something better but can't afford to right now.

Now onto the problem, the gear changes have never been particularly smooth but over the last month they have got worse. The gear changes themselves, while clunky, aren't a particular issue. What is an issue is that it sometimes misses a gear especially 3rd and 6th gears (so when I change from 2nd it will go straight to 4th or from 5th straight to 7th). This is more of an issue as you will think you are in the right gear and then it will snap back into the correct gear later on. This is a particular issue when cycling up hill as it throws my feet off the pedals. I've got massive bruises on both knees from where they have hit the handlebars at these times. This happens when riding on relatively smooth roads so isn't even anything to do with the type of terrain that I am riding on.

I have taken the bike to a shop to be serviced and they seemed to think it was ok but it is still happening. So with that information and the fact that I can't afford to upgrade my bike straight away what can I do to try and solve this issue with gear changes being clunky and gears being missed (or being missed then snapping back into them as I am riding)?

The first thing to check is that the rear derailleur indexing adjustment is good. I.e. the derailleur cage is aligned properly with the individual sprockets in each gear. If cage is moving slightly too far at each shift it could push the chain two sprockets over instead of one. I would expect a repair shop to be able to adjust indexing properly, and bad indexing causes the chain to rattle on the sprockets - which you don't mention - so this may not be the issue.

The next thing to check for is a bent derailleur hanger resulting in the  derailleur cage not being parallel to the sprockets.

Another cause of shifting problems is the shift cable sticking in the housing due to corrosion or contamination, although this tends to cause 'delayed' upshifts (from larger to smaller sprockets) as the derailleur spring cannot pull the cable through the housing.

Just been given the apollo spiral as gears didnt work from day one and then owner was too embarrassed to go back as a novice female rider. I have had a look and the rear mech is intrinsically tighter than it should be and the front derailure has bent as it has caught the sprocket against the chain- It looked too low but on raising it I couldnt convince myself that unbending it would resolve the primary problem.... more likely the wrong radius of the arm for the gear ratios. Either way dont buy this bike.


9/16 pedals wont go in crank - they're too big What about if you have two gears on the crank. I used a 5/8 open wrench to take out my original pedals on my Schwinn Sierra and the new 9/16 pedals won't go in - they're too big. What size would it need? I'd like to use an adapter.

First verify that you are in fact trying to screw the left pedal into the left crank arm and the right pedal into the right crank arm. The pedals are sometimes marked with a R and L on the end of the threaded section. The left side is the side your left hand is on while riding. There are 2 common size pedal threads. Many children's bikes, some lower cost department store bikes and some folding bikes use 1/2" thread on the pedal . Most others use a 9/16" thread on the pedal. My guess is you bought 9/16" pedals and they are too large to screw in to your crank arms. While they make adapters to use 1/2" pedals in 9/16" holes there is not one for the reverse. As an alternative you can ask your local bike shop to determine if the crank arm has enough material to modify it to the 9/16" thread. This likely more expensive them getting the correct pedals.

It's 5/8" pedals .good luck finding them. Mid school mongoose and schwinn used this size pedal for a few bikes and some old school bikes. I have a mongoose crank and I can't find these size pedals anywhere!


Does changing gear relation produce different speed at same applied power? When you are starting the ride, I potentially believe ("know?") that with a smaller plate(cog with fewer teeth in the rear cassette), you obtain more velocity than with a bigger plate(cog with more teeth, in the rear cassette), applying same human power consumption on both cases. In first case (the correct way of starting the ride), the chosen plate radius is small, so it weights less and offers less resistance.

Once bike is running at a normal speed on flat terrain and gear's start resistance has been overcome, I want to know if I will get more speed with a smaller tooth rear cog than with a bigger cog, applying same human power consumption on both cases.  Changing relations would of course mean I should ride faster of slower in order to waste my same power in all cases, basically because the different resistances of the plate, which depends on its chosen radius mostly.

So let's say I want to be using 200 Watts. Would different gear relation setups affect the output speed?

If my statements above are wrong in first please, correct me.

Yay! Another physics question.

Restating the question: if the rider power input is constant, does the bicycle velocity change if the drive-train gear ratio is changed?

Let's assume the road surface, wind speed, gravity etc. all remain constant. Bike and rider are on a surface with no gradient.

Short answer is that constant power results in constant velocity regardless of gear ratio. Gear ratios change angular velocity and torque but because the product of the two is constant power remains the same.

Power at the rear wheel = power provided by rider - power loss in drive-train.

If the power loss in the drive-train does not change with gear ratio selected, the power at the rear wheel does not change and hence velocity does not change.

Of course, the power loss in the drive-train will depend on the gear ratio selected to some degree. I believe the chain travelling more slowly around a larger sprocket consumes less power (I'm not sure on this so somebody please correct me if I'm wrong).

However the power needed to overcome air resistance and wheel rolling  resistance is much greater than drive-train losses (if the velocity is not very low), so a change in drive-train losses will not effect velocity very much.

Update: addressing this statement from the OP (edited), as I think it's crux of the misunderstanding.

...with a smaller [rear sprocket] you obtain [higher] velocity than with a bigger [rear sprocket], applying same human power...

That would be true if human power was replaced with pedaling rotational speed.

I know this is an old question, but I couldn't help jumping in and offering a contrarian opinion.

Of course changing the gear changes the speed! Why do you think they have gears on a bike?! Watch the Tour de France, they all have gears on their bikes. They make their handlebars as thin as paperclips to save weight, but they leave the gears on because gears make them go faster. Period. Different gears can make you go faster or slower in different scenarios. The scenario including terrain, biker fitness, biker weight, bike lubrication etc.

You can try it yourself. Get going at a comfortable rate on a bike in flat terrain at a middle gear. Try switching down to your lowest gear while keeping your exertion the same. You will slow down. Try switching to your highest gear while keeping exertion the same. You will slow down. There is a single optimal gear (for that terrain, bike, and human body) which maximizes the power transfer from your body to the bike and thus leading to the highest speed.

The term for this in physics is impedance matching. These concepts are more discussed in electronics, but there are parallels in mechanical systems, with springs being similar to capacitance, and momentum being similar to inductance for example.

Basically, the idea is that all power transfer systems have some amount of resistance when transferring power from the source (your legs) to the load (rubber pushing on the cement). This is very intuitive when when considering the simple case of a constant torque source and resistance. However, your legs are not a constant torque source they are sinusoidal. And as it turns out, the resistance (technically impedance) of power transfer between the source and the load changes depending on the frequency. The gears effectively adjust the frequency of the power source (your legs) to maximize the transfer of power from your legs to the cement.

Since energy is always conserved, what happens to all the energy that your body generates if the impedance is mismatched? Well, some of it certainly is dissipated as heat from simple friction, but the real phenomenon at play here is reflection. Whenever there is a discontinuity in impedance, some of the energy is reflected back towards the source. When you pedal in the wrong gear, you are quite literally pedaling against yourself. Like pushing your hands together really hard, it will make you tired after a while, but you won't see much effect.


Pedaling in Rear Wheel design I had built a bike similar to this one before. I think many would have this idea, too.

However, for some reason, not many of these designed are commercially marketed.

https://sites.google.com/site/pendalbike/pendalbike

There are several advantages on this design:

More aerodynamic posture
Better up-hill climb efficiency (personal experience)
Less maintenance for the drive train
Less Frame materials (weight are transfer directly through the pedal
to rear wheel, and through fork to Front wheel)

There are disadvantages:

Fewer gears (I doubt this, technology in this Information age should
be more than enough to design a robust Internal Hub gear that support
a pedal axle in the middle)
Cost: Obviously it is not in the stage of mass-production, so the
cost would be high. But I do not see why it should be more expensive
(if not to say cheaper) than a normal bike.

Unless I missed many unforeseen disadvantages, what else could prevent this design from becoming popular in the last 10 years?
What are other disadvantages in comparison with a normal bike that can level the advantages I have stated?

One problem is that the design would not be appropriate for technical riding requiring speed.  Getting behind the seat to push against the pedals would put you out over nothing, instead of out over the back wheel.  The design would be less stable because of that and consequently unsuitable for technical riding. The puts it out for mountain styles of riding.

On the road side, the UCI has been fairly quick to ban anything as non-traditional as this.  While materials improvements and the like are generally the norm, major changes to the geometry of a bike is combed over closely and often thrown out.

New designs take sometime to take hold (Fat bikes are a good example from recent years).  The fat bike market lingered for years because very few companies were producing the tyres, bottom brackets, cranksets, hubs and rims it needed to grow.  Although most of the other parts were standard road and mountain bike parts, key components can be a hold back.  Once these bikes started getting raced regularly, the market and manufacture of the specialty parts took off.

For the design you are talking about, I don't see enough appreciable advantages for the commuter market to champion it.  Since it's not appropriate for the other markets, I can't  see such a radially departing design gaining any traction.

Do not worry about riding stability in pedaling-in-rear-wheel-designs!
¤ as long the hands are placed on the front - so do that as a rule.

And my "pedal-gear-crank-hub in-rear-wheel bicycle" offers several riding positions: on the same cycle; from the upright "uni-cycle" to the low racing posture; even on a very short bike - as shown below, enjoy

So, the rider decides how much weight to put on the rear. In mud or heavy snow you would like load on the driving wheel !

I have years of good experience from riding on several of my Pendal Bike designs.
Please commend and comment.
Enjoy your ride,
Jens Mindegaard


modernizing shifters I want to replace my old lever shifters (Shimano 515) with something a bit more modern. Can I do this without replacing the front and rear derailleurs. And which shifter would be a simple, and or equivalent replacement.

Shimano never made a derailleur or shifter called "515", as far as I can tell. Perhaps you mean "SIS"? SIS stands (I think) for Shimano Integrated Shifting, which is indexed shifting.

The fact that you've only got five cogs in back suggests that you've got an old, low-end bike. You might find that upgrading your shifters will exceed the total value of the bike. I also don't know whether Shimano's low-end derailleurs are compatible with their brifters for indexed shifting. I'd take it by a bike shop and ask for an opinion.

You only need to replace the shifters, but make sure to look for a model that has the same number of gears in the front and back.
When you shift, the indexing happens inside the shifter, not the derailleur. Derailleurs are compatible with all speeds, and even friction shifters.
All you have to do to replace them, is get a shifter with the matching number of gears on your bike.


Does a bike exist that is both very light and does not need to be ridden in a hunched over position? I have a spinal injury that prevents me from lifting anything heavier than about 10 lbs (4.5 kg), and prevents me from being in a hunched over position, without causing myself extreme and lingering (for weeks or months) pain. I miss biking. I am wondering if there exists a bike that is both very light, but also allows for riding in an upright sitting position? So far my searches have turned up nothing.

It's possible I just have to resign myself to not being able to bike anymore, but I am hoping that there is some niche build or light bike that could be modified out there that might be suitable that I have missed in my research so far.

EDIT: the bike does not need to be less than 10 lbs (4.5 kg). I just wanted to give perspective on the necessity for low weight. I weigh about 170 lbs (77 kg)

Here's what you need!  Lightweight and upright --

There are also two options that no one mentioned here:

mini velo that seems to be very popular in Asia;
folding bikes. You can find plenty, from very simple to e-bikes.


Change the angle of the arc of downtube / stem shifter lever to make it an alternative thumb shifter? I want to mount the following SunRace clamp-on shifter set horizontally as a "thumb" shifter on a straight MTB handlebar (22.2mm).  I will remove the left lever and only use the right with the clamp.

The problem is that the lever is not easy to reach because it swings from parallel with the handlebar to straight forward.  I would like to have the angle of the full swing of the lever go from a little towards me to a little forward.

Is there an easy way to change the angle of these stem-mount shift levers (which are almost the same as downtube shift levers) by about 45 deg?

Note (in second pic) that these are meant for stem mount, so there is a cable housing stop for the part of the shift cable housing that goes from the handlebar to a downtube stop.

Note that there are different levers, depends of the final position. For downtube, head tube or steam, see the ilustration in the bottom of the page:

Some of them have the cable stop vertically, equal as the tube hanger, and other at 90 degrees of it.

Although I haven't done it with this specific shifter, some similar designs with a fixed cable stop can indeed be adjusted this way. See for example this instructional video for Gevenalle shifters.


Should I adjust rear derailleur as my chain seems too close to each other I am learning to replace chain and freewheel (So far so good). After I put new freewheel and new chain on, the chain are too close to each other at the back now (as you can see in the photo).

I think I need to adjust rear derailleur, is it right? Or maybe the chain wasn't installed correctly ( I cycled around and think chain install seems not too bad).

The chain is too long. Presumably you did not cut it down to size it when you installed it.

All chains are sold with excess length and must be sized to the bike. The length required depends on the length of the chainstays and size of the largest chainring and sprocket.

The easiest way to size the chain is making it the same length as the old chain. You can also find the required length by putting the chain on the bike on the largest chainring and sprocket (and not through the derailleur). This Park Tool video shows how it's done.

Update after getting info that the new chain was cut to length of old chain:

Don't just shorten the chain and see what happens, you need to follow the sizing procedure to make sure the length is right. If the chain is too short for the large chainring/largest sprocket bad things will happen if you attempt to change into that combination.

Before you do that, check that your derailleur has enough total capacity for the chainrings and sprockets you have. Your derailleur looks like a short cage version and may not be able to take up the chain slack necessary.

Total capacity needed is:

(difference in teeth between largest/smallest chainrings) + (difference in teeth between largest/smallest sprockets)

If you have a Shimano derailleur you can look up the specs here. Note there is a link to archive spec docs if you have an older model. If you don't know what model you have or can't figure it out post a pic of the derailleur in your question, and tell us road or MTB and how many cassette sprockets you have and someone will likely identify it for you.

People are making this way too awkward and complicated.
Just use your old chain as a guide to how long it needs to be and remove the excess links with a chain link remover and not cut the chain to length as some people have said.
Then install the new chain....simple!
I love how people over complicate this procedure.


How should one cross the IJ river with a bike? The IJ river flows through Amsterdam. Well, actually, it flows North of historical Amsterdam, but these days there's a Northern borough.

I've never been north of the river before, and I'm going there soon. I thought I'd take my bike, but they're not very amphibian, and it occurred to me I don't know whether I can safely cross anywhere...

OpenStreetMap shows a path but there doesn't seem to be a bridge there, nor a tunnel
There's the IJtunnel, but I don't know whether I can cycle through it, nor whether it's a good idea with the car smog
There are ferries, but I don't know whether these allow bikes and whether it's too pricey to be worth it.

What are my options?

(Yes I know I can just cycle around the bank and see, or also ask around, I'd just rather plan ahead.)

The route that you highlighted on the map is the ferry route. It operates 24/7. It allows bikes and it is completely free.

More info about ferries in Amsterdam.

There is also bridge on the east of Amsterdam.

And there are plans to build bike tunnel close to IJ tunnel.

Yah, from my time in Amsterdam one of my favourite days out was to hop on the ferry behind centraal station and then head north. Superb riding, recommend Marken as a suitable destination. Ferry is free and quick. Or it was 8 years ago.


Why does shifting under power affect shift quality? I recently was attempting to shift up a hill and observed that

The shifting levers on the handlebars displayed significant resistance to my pushing them.
Despite several rotations of the crank, the bicycle had not shifted gears.

Googling around, I've seen people claim that pedaling under power increases chain tension and that this chain tension will affect how easily the chain moves between gears.

Intuitively, this does not make sense to me, as how easily the chain moves orthogonal to the direction of travel (i.e., the ease of shifting) would seem to be independent of the chain tensions parallel to the direction of travel. This seems to imply there's a causal relationship between the relative magnitudes of these forces.

Moreover, given that the chain itself is the same length regardless of the power transmitted, it's unclear to me how pedaling increases chain tension. Is it that one part of the chain becomes more tense, and the other becomes less tense? A free-body diagram type explanation would be very helpful.

How might one understand or model the shifting action and mechanism in a way that explains why chain tension affects shifting?

There may be other factors that affect "shift quality", if I understand what you meant correctly, but the most significant by far is “direction of force applied.

Basically for a gear to change the mechanism just pushes the chain “off rail” enough in the direction of the new gear. When the chain has a higher tension applied on it the derailleur doesn’t have enough strength to push the chain “off the rail”. (Derailleur is the name of the part the pushes the chain)
If you still haven’t understood, imagine a line stretched between two fixed poles, if it is loose and you push it to the side it will move some, if it has a higher tension and you push to the side with the same strength and direction than before it will move less. And the tighter the line the less to the side it would move. A gear system has a minimum distance that it needs to move to the side so it can change gears.

More advanced, modern and obviously expensive have over time placed gears closer to each other and shaped individuals to make the “derailing” need a smaller push in a new direction, requiring less strength to push the chain and as a whole make the process more smooth.

If you didn’t understand something just ask.

The other answers give you a good idea. But not addressing the issue. People don't use the gears correctly.
Tension on the underside never changes that much. It is the tension on the top. Friction holds the chain in the cog seat caused by tension pressure. Bad use of gears result in rounding of the teeth. Mainly because of over exerting of power in the give gear. The rear gear set is not meant for constant gear changes. It is rather a optimising gear. The front is designed for constant and rapid gear changes. You are fighting to move a chain up hill under strain if you wish to use the rear set for climbing quickly. Best is to set the rear at a comfortable gear and do rapid gear changes with the front. Also as others have pointed out, you need to ease off a tad for a second during gear changes. You will greatly increase the life of your running gear, as well as easier, quicker gear changes.


Is there any other size tires that will fit on a 27 x 1 1/4 rim? I live in a city with plenty of cycling shops, but they are all out of 27 x 1 1/4 tires. Each shop gives me a different answer about the possibility of using a different size of tire. Can I fit a different size onto an old 27 x 1 1/4 rim?

You need 27 x (some number of inches given as a fraction). So 27x 1 1/8 would fit, 27 x 1 1/4 would fit, etc. Other sizes won't fit. As dlu's answer points out, an easy way to get this right is to ask for ISO 630 tires.

That being said,  27 x 1 1/4 tires are still made in plenty by brands like Continental, Bontrager, etc. so your bike shop should easily be able to order one for you in a few days, or you can buy them online.

See Sheldon Brown's page for details on how tire sizing for bicycles is a mess.

"Brown's Law Of Tire Sizing:

If two tires are marked with sizes that are mathematically equal,
but one is expressed as a decimal and the other as a fraction,
these two tires will not be interchangeable."

Sheldon has another interesting note: Very old (60's) 27" rims had straight sides versus modern hooked sides, so they can't run as high pressure. However, he says if you get a tire which says hook edge rims only, you can put it on an older straight rim, just not at as high of a pressure.

Finally, tubes for 27 x 1 1/4 tires are a different matter. You can use 700c tubes in 27 x 1 1/4 tires (The right size should be 700 x 28-32 ish -- the boxes will be marked accordingly depending on the brand).

Dude , 27 x 1 1/4 tires are quite available on the net....in this day & age local shops might defer to all whatever is the new thing 28" et cet & not stock as many 27 x 1 1/4 if at all due to the local demand...I have heard that you might go a size smaller but that's on you NEVER GO Larger....Smaller or larger equally...if you have to zip & shake to avoid a spill & the tire comes off the rim & you get T-Boned..& sue the tire manfact. their atty. will just hold up your rim & the tire (size) you had on to Da Judge & you lose & have to pay the other's attys fees & costs..SAME with Tires that state "Hooked Rims are necess for a proper fit...Smooth side'd rims not reccm"d" . If there is NO warning , no red flag..about the tire & hooked rims...don't worry...ONLY if there IS.. Bike Co's might tell you that they have sold thousands of Hooked rim Tires to smooth sided rim Owners with no complaints  I REFER you to above "zip & shake"..If a Tire Manfg makes a note of "proper fit with hooked rim" , that's to CYA himself not to help you...it's a red flag warning ! Proceed at your own expense....Cause that's what their Atty will hold up to Da Judge...Your Smooth Sided Rim & Their warning...Again "U" Lose.......BEST , go with your tire size , your rim size & your tube size....They should all be the same . NOT what someone is trying to sell you to clear off what has been sitting on their shelves...Riding a Bike , everyone is coming at you..no need for you to help them take you out


Help identify this mixte A mixte frame with bcn stamped on front, 224 stamped on bottom of frame, Mafac racer brake calipers, Simplex shifters, Suntour derailleuers and hubs, Weinmann brake levers.

Just a guess, but it looks a lot like a motobecane to me.

It's clearly a workshop bike from the 70's, numbers are not SN but references for the tubing. It's merely impossible to go further in part because there has been obvious part replacement (front rear) and common old parts (brakes).

Sorry


What is wrong with my Shimano 105 5800 front derailleur? Background:

I've installed a complete new 105 group (this bike is a brand new custom build) on a Civia Hyland frame.

The rear wheel has a white industries CLD disc hub for the 11 speed cassettes.

The Civia doesn't have a brazed on cable stop, so I've installed a clamp on cable stop on the down tube for the FD cable.

I have an inline barrel adjuster at the cable stop. The Civia has adjustable dropouts, so I've put them as far back as possible, resulting in an effective chainstay length of around 435mm or so. The wheel is in the correct orientation, I've checked side to side length (wheel edge to downtube) and it lines up with the downtube.

I've installed the FD according to the shimano FD shop manual for this dérailleur.

The FD is a clamp on version.

I have plenty of tension, the FD (5800) shifts great and fast, the problem is rubbing.

I can actually adjust the FD so that BOTH the small front/large rear and large front/small rear rub on the FD. I can adjust it so that it rubs at both extremes! Note that I don't mean the cross-chained extremes here, i.e., big/big and small/small, these are ok with the trim positions (I also don't care about these, since I don't use them)

When in the small/big combo it rubs on the inner part of the FD cage. When in the big/small combo it rubs on the outer part of the FD cage.

I'm sure it isn't in a trim position. I'm using a 5800 shifter. I've tried both cable adjuster positions at the pinch bolt. There is slight runout on the big chain ring, but it is pretty small.

In the small/big (front/rear) combo, the chain rubs on the inner part of the cage. In the big/small combo, the chain rubs on the outer part of the cage. It is like my shifter isn't pulling enough cable on the final trim to big shift, or that the chainrings are actually spaced too far apart (I suppose I should pull the crank off and check the latter).

This also occurs with both adjustment screws backed all the way out, to ensure that the full shifter cable range is being utilized.

The chainline is correct at 43.5mm.

Has anyone else seen this problem? Do you think I have a bad shifter?

I've been riding the bike and really took a look today at the shifting while riding.

In the big/small combo, it looked like it just wasn't pulling enough cable to get it over far enough.

While I was riding I had an idea, perhaps the cable position coming from the cable stop had an effect (it should since it is basically a projection of the pull onto the the FD lever arm).

The cable stop was a clamp on aftermarket one, since the Civia Hyland doesn't have cable stops.

When I got home I decided to test it some more. I did two things :

moved the cable stop up and down
rotated the cable stop around the down tube

I managed to find a position where it worked! Barely, the tolerances on this thing are tight, but I can get it positioned where it barely doesn't rub now on small/big and on big/small.

The cable stop was too close to the FD, it needed to be moved down.
The cable stop was rotated too far away from the FD, it needed to be rotated closer to the centerline of the downtube.

This fixed the problem, these new FDs have very tight specs, it still barely, barely doesn't rub.

At least I have a cable stop that I can move around, if the cable stop were in a fixed position I couldn't have fixed this.

Its very unlikely to be the shifter.  Much more likely you've not got it adjusted quite right.  If its rubbing when you have it in the big ring at the front and small ring at the rear there are a couple of things to check: is the FD cable tight? If so then maybe the small screws on the FD that prevent the mech from moving too far need adjusted.  Other obvious questions would be whether the shifter is for a double or triple (dont think you said) and 8/9/10/11 speed, as these would potentially result in a problem if the shifter isnt compatible with the driver train.


Can I use a road bike for commuting 11 miles each way without SPANDEX I am thinking of getting (investing in) a road bike for my 11 mile commute (total 22 miles each day).  I want to continue wearing normal work clothes - meaning hiking pants and a T-Shirt.  I plan on using the Spiderflex seat (taken from my Mountain Bike) on a road bike.

The Spiderflex eliminates any seat pain, and there is no chafing, ever.
Can this be done? Does anyone do something similar?

Yes, absolutely.

Clothing is mostly an issue of personal preference.  Performance fabrics and things like spandex don't make that much difference for short stretches, and their advantages become more pronounced and valuable the longer you ride.

11 miles is somewhat of an intermediate distance; in regular clothes you'd be totally fine, assuming that the weather and the road conditions won't make your work clothes sweaty or dirty by the time you get there.   For commuting to work, I'd make the decision more on the basis of road conditions and comfort.

No.

In my experience it’s uncomfortable and pants tend to get caught in the chain and bottle cages.


What to do when a snake is in front of you? I was coming out of a corner and saw something on the road about 10 meters up but only from about 5 meters I realised it's a snake trying to cross the path.

I panicked but didn't really do anything. Fortunately, it crossed the past quick enough, I just ended up so annoyed/scared.

What's the best action in that situation? Accelerate as hard as you can, while trying to avoid it? Or aim for it? I was too afraid that if I stopped it might chase me.

Stop. Back up if necessary. Don't risk running over it. Snakes almost never chase people, they will only attack if they're cornered or you're lying very still (for very large snakes that eat things the size of people).

Running over a snake is probably your worst approach if you don't want to get bitten. Not only do you have to be very close to the snake, you're going out of your way to threaten it. Almost any animal in that situation will try to attack you, purely to stop you killing them.

I've seen several snakes, one on my commute route. For me that's a chance to stop and go "Wow! A snake!" and maybe get my camera out so I can take a photo from a safe distance. But even snakes that aren't venomous are best left alone. Either because they're wild animals that you respect and want to encourage, or because the gap between non-venomous and harmless is significant. A bite or accidental impact from a snake can still injure you.

Also, many are protected, and I'm not sure whether being bitten by a venomous snake is actually worse than being prosecuted for interfering with one.

You are above the ground moving at speed and pedaling.

If it is not a striking snake it cannot even get to you.

A striking snake would need to prepare and then not just hit your forward motion but also the spinning pedal. A predator is not going to hunt from the middle of a path - they hunt from cover. Once a snake is aware of your presence they will typically move on. If the snake coils or moves into a striking stance then give it space. They can strike about 3/4 of the body length.

If you came across a coiled snake in a path then stop if you can or otherwise run it over. If they are prepared to strike then don't give them an angle on your leg.

Snakes do not hunt from a path.  They hunt from cover.  If you see them first and avoid you are safe.  This a snake sunning or just wanted to get to the other side of the road.  And probably not even venomous.

4 down votes?  Let's consider nature.  How does a horse deal with a snake?  First they avoid.  If they cannot avoid they come straight at it with all 4 hoofs. Your tire is your hoof.

Even a freshly killed rattle snake will strike from muscle reflex alone when  touched. If you are going to remove even what you think is a dead snake from a trail then use a stick unless you know from visual inspection it is not poisonous.

I rode dirt bike in rattle snake country and came upon a few rattlers. They can coil fast and unless you have a lot of speed (like motorcycle) they will be ready for you as they feel vibration in the ground. If they are flat they are probably not a predatory snake. At bicycle trail speed they can can coil and strike faster than I want to take chances. Even a non coiling predatory snake will face you in sprung like position. They can strike a rabbit. I am not giving them an open shot at my leg.  Within striking distance of coiled snake snake is not a position you want to be.  Front wheel first so they do not have a vector to your leg is the best defense. If you can avoid striking distance then go for it.  Otherwise your best out is over the top.

If a snake is hunting from cover they will size you up and avoid wasting venom.  Like I said they don't hunt from the middle of a path. If they were in the path they were sunning or crossing.

A poisonous snake like a coral that is not a striking snake is not a much of a bicycle threat and they are secretive snakes. Not likely to find them on a path. And they are going run rather than go into an attack position.

strike video


Help identify this vintage bike I would appreciate help in identifying this bike.
I was thinking the bike could be a Raleigh as they are common in the UK however the moulding on the tubes is strange to me. I'm guessing the bike is from 1979 based on the sturmey-archer hub having a 79 and 4 engraved.
Any further information on the bike would be really appreciated.

The following link provides the same photos.
https://photos.app.goo.gl/ejkchd1vtSSiqGbRA

That bike has certainly had some changes since it was new.
I can see someone brush-painted it green, without bothering to remove the outers for the gear cables or the brake calipers, though they do appear to have missed the cranks when painting.
The cranks are cottered, so those are probably 70s or earlier.   The pedals may be newer than that - they're not clear in the photo.
Your bike was probably a drop bar when new - the flatbar look like that wasn't done - if you wanted an upright position, you got a dutch-ier style of bike with more rise and sweep in the bars.   Point is, the flat bar is probably a much more recent change, along with the shorter quill stem.
On the other hand, I suspect the saddle is from an older bike too - the saddle rails have that green paint slathered on, but the style of the rails and springs is not in line with the frame.  So I suspect the big sprung-saddle was swapped in somewhere midlife.
The wheels look odd too - the rims have a "look" of aluminium in your photo, this can be tested with a magnet which will stick to steel rims and not aluminium.  They would have been "28 inch" when new, and I can see the brake calipers are not at their limits so probably still are 28 inch, or ETRTO 630mm diameter.

Could you check the Right hand side of the rear dropout for a derailleur hanger?  If you find one, or remains of one being cut off, or even the dual imprint of a crow's foot hanger in the right dropout, then thats a sign it was originally sold with a derailleur.
That the SA hub has "79" on it suggests the hub is that old.  But the bike's frame appears to be older again to me.  I'm very confident the bars were changed, fairly confident the saddle was changed, so theres every possibility the rear wheel was swapped out too.

It does have the overall look of a Raleigh frame, but that's common with many other english frame designs too.  The long curve on the fork means its a riding bike, not the fast twitchiness of a race bike.
I'd be concerned about the slap-dash paint job.  Someone's not bothered removing parts before painting, so they're likely to have not bothered removing or treating rust before painting either.  Have a good look over the whole frame, looking for anything soft.
I found a reference to Davies Components:

Davis Components was a Birmingham based company who manufactured lugs and frame fittings such as your bottom bracket. The numbers "61 .. 64" typically refer to the angles.
From https://www.bikeforums.net/classic-vintage/755602-frame-stamped-davis-components-who-were-they.html

So they made parts, not whole bikes.   Thus Raleigh would not have this, because Raleigh was an integrated vertical who made everything for themselves.
If you really want a name on your bike, get a water decal or sticker make saying whatever you want.   "Richard's Bike" is accurate, or you could call it "The Incredible Hulk" or even "Cervell-faux" or "Heck" or "cannoodle".


Are there any scientific studies proving the benefits of clipless pedal systems? Have there been done any scientific studies that proves that clipless pedals actually improve pedaling efficiency etc. over flat pedals? Clipless pedal enthusiasts are quick to say that you must use clipless pedals to improve efficiency when cycling, but I have never seen this being backed up by any scientific sources actually proving this claimed efficiency boost.

The Pedaling Technique of Elite Endurance Cyclists: Changes With Increasing Workload at Constant Cadence was published in the International Journal of Sport Biometrics 7:29-53, 1991. However, it seems to come to the conclusion that they don't really make any difference as far as pedaling efficiency goes.
"...while torque during the upstroke did reduce the total positive work required during the downstroke, it did not contribute significantly to the external work done because 98.6% and 96.3% of the total work done at the low and high workloads, respectively, was done during the downstroke."
This is echoed in Physiological and biochemical determinants of elite
endurance cycling performance published in the Medicine and Science in Sports and Exercise 23:93-107, 1991. There are numerous graphs showing that pedal force is only exerted between the top and bottom of the downstroke, represented by a very sharp parabola spiking at 90 degrees from vertical.
That said, I think it's obvious to anyone who has ever done any particularly technical riding with and without clipless pedals that clipless pedals significantly improve the handling of a bicycle. A fact which is probably more difficult to verify through scientific studies.

Not at all, the idea the 'clips are more efficient than flats' is based on nothing but superstition and urban myth. It's like now every rider laughs at the idea of using toe clips and wonder how cyclists could have put up with them, it was 'more efficient' back in the day. Like so many things in cycling using clips is just another superstitious practise in cycling with no scientific backup, despite even the best pros can't avoid crashing dozens of times a year using clips, they still don't give it up, and velodrome riders having to be held up at start of the race like children on stabilizers. (they may as well use stabilizers if they can't keep feet on the pedals during riding.)

GCN has done three tests on the matter, and all three show that flats are more efficient/faster than clips. I think the reason may be that as you use the hamstrings to pull up with clips, you also waste quad muscles unnecesaryly because muscles are all connected as you use the quad you also use the hamstring etc., So with clips your quads never gets a complete rest tiring you out quicker. (probably more so in climbs, which is why even pros climb so slowly) where as with flat your quads (which contribute more than 96% of the power) gets a complete rest every half rotation.

Also when you push down, you stabilize the bike and propel it forward. Upstroke is not efficient because it 'lifts' the bike up losing momentum and balance, which is why you see clip riders swing a lot from side to side (losing energy) when climbing and sprint.