From: truesdel@ics.uci.edu (Scott Truesdell)
Subject: Re: Help! Freewheel wear!
Newsgroups: rec.bicycles.tech
Organization: ICS Department, U.C.I.
Distribution: usa
Date: 18 Dec 92 03:49:29 GMT
Followup-To: rec.bicycles.tech

In article <1992Dec17.171803.26067@icaen.uiowa.edu>,
sbtaves@icaen.uiowa.edu (Steven Bradley Taves) wrote:
>
> I was told when I bought the bike that I should replace the chain
> about every 4  months.  But I didnt get around to it until this week, which
> makes it about 6 or 7 months.

It's really the hours and intensity of riding that matter... not an
arbitrary measure of time like you were told. For it to go that bad you
must be a truely gonzo rider!

Here's the rule of thumb for replacing your chain. The links are exactly
1/2 apart. Measure twelve inches of chain. If the chain is more than 1/16"
longer than landing on an even mark replace it. After this, component wear
is accelerated. Many say that even 1/6" is too far. I use Sedis ATB chains
and buy them for $9.00 2 or 3 at a time when they go on sale. I use one
about every six months (3 offroad rides/week during daylight savings time,
1.5 offroad rides/week during the dark months).


> Now I have chain slippage when I get on it
> (pedal hard). I was told that it was the rear sprockets wearing with my
> old chain that now makes them incompatible with my new chain.  And I was told
> that I would need to replace the chainwheel and, freewheel, which would run me
> over $100.

I'll start with a summary:

1. old and new chain have same number of links? (same overall length?)
2. determine where the chain is skipping, front or rear. Most pprobably
   not both. The rear gears are made of harder metal.
3. buy only the parts (and maybe tools) you need. If it's only your rear
   you can do it yourself for less than $30 parts and tools. Front, not
   much more.

First, a maybe obvious question: is the new chain the same length as the
old chain? If the chain is too long or too short you will experience all
sorts of odd behaviour.

Second, it's up to you to determine where the chain is slipping. You have
to determine whether the chain is slipping over the rear sprockets or over
the front chainrings. It's almost certain that you don't need both. Rough
ballpark prices for each are mentioned below.

Look at the teeth on the gears. They should be symetrical when viewed from
the side. Here is an attempt at ASCII graphics:
    ___       ___       ___             __        __        __
   /   \     /   \     /   \           /  \      /  \      /  \
   |   |     |   |     |   |           |   \     |   \     |   \
  /     \___/     \___/     \__      _/     \___/     \___/     \__

            G O O D                             W O R N

And it can be worse. The trailing edge can be peened over making the teeth
look 'hooked'.

While you at it, sight down the gears fore and aft plane. There will most
likely be some designed-in assymetries but look for peened-over and burred
teeth. These won't cause the chain to skip but it can cause 'chain suck'
and poor shifting performance. These kinds of burrs can be dressed with a
fine file to extend the life of the gears.

The rear cluster costs about $20. You need a special splined socket and a
chain whip to remove and install it: $7.00 each. It's really easy to do.
You can do without the chain whip by using your old chain to hold the rear
cluster. It's more difficult than using a 'store bought' chain whip but it
can be done. Look at the chain whip in the store and fabricate your own...
they're pretty primative tools!

In all likelihood you won't need the biggest chainring, only the middle and
small ring. They cost about $20 and $15 each. The hard part about changing
these is that you have to pull the cranks off the bottom bracket spindle.
The tool costs about $15 but a friendly shop MIGHT pull them for you if you
bought the parts from them.

So, given worst case (new rear cluster, two new rings and two tools) you're
looking at $84. You can probably beat those prices.


> Can I somehow tighten my chain?

No.


> Should I put my old chain back on?

Sure, if what I said up higher won't work for you. Ride it til it craps out
totally. If you really do already have to replace everything it can't get
any worse.

Other ideas: I use up a granny gear (the smallest chainring) every 4 to 6
months. I weigh a ton so this isn't all too surprising. I replaced it a
year ago with a stainless steel chainring by Specialized for $12.99. Sure,
it's marginally heavier, but I haven't had to touch it and it shifts smooth
as glass.

  --scott
Newsgroups: rec.bicycles.tech