Newsgroup: it.hobby.motociclismo
Titolo: [TECNICA DI GUIDA] La frenata (lungo) - da rec.motorc.harley

Riporto ancora da rec.motorcycle.harley un articolo (in inglese) su come
frenare in moto, tratto da un manuale della polizia USA.
Non l'ho ancora letto tutto, ma è molto probabile che parte di quanto
riportato sia applicabile solo a certe moto e/o a certi tipi di strada. In
ogni caso credo che contenga degli spunti interessanti.
Sulla sua validità non mi pronuncio, vedete voi; io mi limito a riportare.
C.
--
Barkeep, Shirley, and loyal patrons of the VB&G. Drinks in a
moment... In an earlier thread "Which Brake Do You Use?" I offered to
type up some relevant advice from a book - Motorcycle Roadcraft: the
police riders handbook to better motorcycling. I did say at the time
that it was nine pages (more fool me) Anyway several people seemed
interested, and suggested options for making it more widely available.
I ended up typing it out and dumped it all in here for two reasons: 1)
It reaches the wider audience 2) It helped me to take it all on board
for when I take my advanced motorcycle test. I'd like to get
everyone in here a drink or three, I'll leave the card behind the bar
so you all can run up a tab on my account.
Braking And Changing Gear
The sequential gearbox on a bike does not allow intermediate gears to
be missed when changing up or down. When speed is lost through
braking, multiple changing down of gears is often required. There are
two techniques which can be used to do this:
block changing
sequential changing.
If, because of inadequate planning, you brake late and rush a gear
change, you risk destabilising your machine exactly when you need the
greatest stability for negotiating the hazard.
Block Changing
During the later stages of braking, hold in the clutch lever and
change down the gears until the appropriate lower gear is selected,
then release the clutch.
This technique allows rapid movement through the gears, but depends on
correctly choosing the appropriate gear for the road speed and
accurately counting the gears. If too low a gear is selected there is
a risk of locking the rear wheel and causing a skid.
Sequential Changing
As speed is lost during braking, work down through each gear, engaging
the next lower gear as its optimum speed range is entered.
At each stage, accurately match the engine speed and gear to the road
speed. This promotes smoothness and avoids locking the rear wheel.
With this technique, engine braking helps slow the machine. The
appropriate gear for the speed is engaged throughout, and because the
drive is engaged except during changes, the bike remains stable. The
rider also has the option of immediate power if needed.
Key Pointers To Skilful Gear Use
Recognise when to change gear by the sound of the engine.
Choose the right gear for the road speed.
Develop good coordination of hand and foot movements.
Brake in good time to slow to the right road speed as you approach a
hazard, and passing through the intermediate gears, select the
appropriate gear.
Use the brakes rather than the gears to slow the machine (except
during hill descents and when there is a risk of skidding).
SLOWING DOWN AND STOPPING
You need to be able to slow down or stop your machine with it fully
under control. The smoothness of a ride is greatly improved by early
anticipation of the need to slow down or stop, and by slowing gently
and progressively. The ability to accurately estimate the required
stopping distance at different speeds and in different conditions is a
central skill of safe riding, and one which you should strive to
develop. There are three ways of slowing down or stopping:
decelerating (closing the throttle)
using the gears (recommended only in slippery conditions)
using the brakes
Deceleration
Deceleration (often called engine braking) is an important way of
slowing a bike. When you close the throttle the engine slows and by
means of engine compression it slows the rear wheel. This reduces
road speed smoothly and gradually with little wear to the machine.
The lower the gear the greater the loss of road speed.
If the throttle is closed smoothly, engine braking provides a stead
and smooth braking effect. It is particularly useful in conditions
where the brakes might lock the wheels - on slippery roads, for
example. Engine braking is also used on long descents in hilly
country.
Engine braking operates only on the rear wheel. Despite this, it is a
very effective way of losing speed. You should consider rear
observation whenever you plan to use it.
Using The Gears
The use of the gears to slow down in slippery conditions requires
sensitive control of the throttle and clutch. The technique makes use
of the greater engine braking capability of lower gears. It operates
only on the rear wheel.
To use this technique, select a lower gear and, before the clutch is
released, use the throttle to match the engine speed to the selected
gear and road speed. Release the clutch smoothly. After the clutch
is fully released, reduce road speed by gradually closing the
throttle. Any jerkiness caused by mismatching the engine speed to the
road speed, using the clutch unevenly or decelerating too rapidly,
risks causing a skid.
Using The Brakes
Use the brakes when you need to slow more quickly than you are able to
using engine braking. Correct use of the brakes on a bike can slow
you quickly and effectively. Incorrect use can cause you to collide
or lose control of your machine unnecessarily. Research shows that
19% of all riders do not use their front brakes even in an emergency.
Other research estimated that 30% of accidents could have been avoided
if the brakes had been used to their full capacity.
Follow these guidelines for braking:
brake firmly only when travelling in a straight line
brake in plenty of time
adjust brake pressure to the condition of the road surface
avoid using the front brake
    - when the machine is banked
    - when turning
    - on loose or slippery surfaces
on hills, brake on the straight stretches and ease off on the bends.
Brakes On A Bike
Each wheel of a motorcycle supplies a different amount of braking.
Under braking, the weight of the machine shifts forward onto the front
wheel, improving front tyre grip and reducing back tyre grip. The
largest braking effort is produced by the front wheel; a smaller but
significant amount is produced by the rear wheel. In normal
conditions optimum braking is achieved by using both brakes, applying
the front brake momentarily before the rear.
Braking effort has to be applied to the two wheels with great
sensitivity and discrimination. The shift in weight off the rear tyre
onto the front tyre means that it is relatively easy to exceed the
amount of tyre grip available at the rear tyre. Excessive pressure on
the rear brake will cause the rear tyre to lock. On a bend this will
cause the back end to swing out and will destabilise the sideways
balance of the machine.
Some riders are reluctant to use the front brake in any conditions
because they fear the possibility of locking the front wheel. This
means they lose most of their braking capability. There are a number
of situation where you are advised to avoid using the front brake but
this is not rigid advice. As you develop experience and your feel for
your machine improves, you will develop the ability to use the front
brake in adverse situations. It is a question of your awareness of
the tolerances of tyre grip and of your finesse in operating the
controls. Reliance on the rear brake alone has serious disadvantages.
Using it alone, especially under hard braking, causes the rear wheel
to rise, lock and bounce along the road. This greatly extends the
braking distance and destabilises the bike.
The best combination of front and rear braking varies with speed,
direction of travel, and road surface conditions. General advice on
which combination to use is given below:
gently take up the initial free movement of the brakes
distribute and increase pressures progressively as required
relax pressures as unwanted road speed is lost
release the pressure just before stopping to avoid a jerking halt.
When to apply the brakes and by how much depends on your speed, the
space available, the road surface and your assessment of the
appropriate speed for approaching the hazard. Braking should normally
be progressive and increased steadily until most of the unwanted speed
has been lost; pressure on the brakes should then be decreased to
ensure maximum smoothness.
During cornering
Braking is hazardous during cornering because it affects the stability
of the machine and may cause the wheels to slide sideways. If this
happens there is always the possibility that the machine may fall
over. If braking is necessary, brake gently and steadily adjust the
brake pressure according to the condition of the road surface and
avoid locking the wheels.
Generally, plan to brake in plenty of time on the approach to a corner
or bend. Avoid braking while cornering.
On poor surfaces
Where the surface of the road is poor and grip is reduced, for
example, because of loose gravel, damp, rain, road paint, leaves or
dust, brake on the part of the road that provides the best grip.
Adjust the intensity of your braking according to the immediate
surface conditions, increasing pressure on a good surface, reducing
pressure on a poor one. Where the surface is uncertain, avoid using
the brakes and rely on engine braking to slow down. Gently use the
back brake to bring the bike to a final halt.
This level of response to surface conditions requires intense
observation and intelligent anticipation.
Emergency braking on a good dry road
In an emergency, assess whether you can steer out of trouble or
whether you have room to brake to a standstill on a straight course.
The quickest and shortest way to stop on a good dry road is to brake
to a point just before the wheels lock (technically, the point at
which there is 15% wheel slip). Brake as firmly as possible with both
brakes but avoid locking either wheel. As the machine slows gradually
relax the pressure on the front brake and increase the pressure on the
rear brake.
If the machine is banked, and time and space permit, try to return the
bike upright. Apply the rear brake and avoid using the front brake
until the bike is upright. If there is a choice between braking hard
or colliding, apply the rear brake hard and lean the machine further
over. If the front brake is used other than lightly, tyre grip will
be lost and the machine will slide outwards.
On machines fitted with an antilock braking system, firmly apply the
brakes. Do not release them as you feel the system come into
operation. The brakes need to be fully applied for the system to
work. Do not be alarmed by the pulsing sensation felt while ABS is
operating.
Emergency braking on a slippery road
Emergency braking on a slippery surface should be avoided wherever
possible. It is much better to avoid having to brake in these
conditions by using thorough observation, anticipation, and early
adjustment of speed. If it is necessary to brake and the machine is
upright, distribute your braking effort almost equally between the
front and rear brakes. When the machine is banked, only use the front
brake as a last resort.
Machines fitted with linked brakes and an antilock braking system can
be braked heavily when upright on a slippery surface and remain
stable. However, braking distances are greatly increased. This
technology does not justify poor riding technique or taking greater
risks.
Testing Your Brakes
Every time you use your machine check that the brakes work. Do a
stationary check before you move off, and check them again when you
are moving.
The stationary test. Check that the hand lever and foot pedal move
freely and give a firm positive pressure.
The moving test. Make sure that the brakes are working efficiently
under running conditions. Choose a flat, level road with good surface
conditions and no other traffic. Bring the speed up and apply both
brakes. Adjust your braking effort to the existing surface
conditions. Until you have done this test keep you speeds low and
brake early for any hazards. If you are on the same machine all day
you only need to do this test once, provided you have no reason to
suspect the performance of the brakes. Always consider the safety and
convenience of other road users before you do a moving test.
The Safe Stopping Distance Rule
This is one of the guiding principles of 'Motorcycle Roadcraft' and
should always be observed. By relating your speed to the distance in
which you can stop, you can assess the safety of your speed in any
situation. *NEVER RIDE SO FAST THAT YOU CANNOT STOP COMFORTABLY ON
YOUR OWN SIDE OF THE ROAD WITHIN THE DISTANCE YOU CAN SEE TO BE
CLEAR.*
The importance of this rule for your own and other people's safety
cannot be overstated. It provides a guide to the speed at which you
should corner, and it indicates the speed and distance you should keep
from other vehicles in all other traffic situation. Successfully
applying this rule requires skill. You need to be aware of:
the braking capabilities of your machine
the type and condition of the road surface - in slippery or wet
conditions braking distances increase greatly
the effects of cornering, braking and machine balance on tyre grip.
The only variation to this rule occurs in narrow and single track
lanes where you need to allow twice the overall stopping distance that
you can see to be clear. This is to allow sufficient room for any
oncoming vehicle to see you and also brake.
Overall Safe Stopping Distance
To work out the overall safe stopping distance add thinking distance
to braking distance.
*Thinking distance + braking distance = stopping distance*
Thinking distance is the distance travelled in the time between first
observing the need for action and acting. The average rider reacts to
expected events in 0.7 seconds. The distance covered in that time is
the same figure in feet as the speed in miles per hour; for example at
30 miles per hour thinking distance is 30 feet.
Actual thinking distance varies according to the speed of the machine,
your physical and mental condition, your attentiveness and whether or
not you are expecting something to happen. Everyone takes much longer
to react to unexpected events than to expected ones.
Braking distance is the distance needed for braking in dry conditions.
You should be familiar with the braking distances for different speeds
recommended in the 'Highway Code'.
Actual braking distance depends on the machine's capability, the
gradient of the road, the condition of the road surface and how you
use the brakes. Rising or falling gradients have a significant effect
on deceleration and braking distances. Slippery surfaces greatly
increase braking distances.
The Two Second Rule
One way of keeping a safe distance on fast roads is by leaving a gap
of at least two seconds between you and the vehicle in front. An easy
way to count two seconds is to say - Only a fool breaks the two second
rule.
This time should be at least doubled in wet weather and further
increased in icy conditions. If the vehicle behind you is too close,
drop back further from the vehicle in front. This will allow you to
brake more gently in an emergency and may prevent you being rammed
from behind
Braking As You Approach A Hazard
To apply the system of motorcycle control you should consider your
road speed on the approach to a hazard and adjust it if necessary. If
you need to slow down, consider rear observation, adopt the best road
position and then reduce speed safely and smoothly using deceleration,
braking or a combination of both.
When and how firmly you apply brakes depends on your judgement of
speed and distance. You should consider:
your initial speed
the road surface
the degree of cornering
weather conditions
the specific road and traffic conditions.
Sometimes braking may need to be firm but it should never be harsh.
Harsh braking usually indicates poor observation, anticipation and
planning. Aim to lose speed steadily from the first moment until you
achieve the right speed to negotiate the hazard. Timing is crucial:
avoid braking so early that you have to re-accelerate to reach the
hazard, or so late that you have to brake forcefully.
--------------------------------
Inviato via 
http://arianna.libero.it/usenet/

 come frenare in moto, tratto da un manuale della polizia USA.
l'ho letto di sfuggita, ma mi pare di capire che spieghi quello che un 
essere umano dotato di cervello impara nei primi 1000 km di moto. devo 
credere che le pattuglie motocicliste della polizia americana sia cosi 
imbecille ? oddio, CHiPs docet eh... :)
-- 
Camillo, BG, a piedi.


Ovvio che non spiega le staccate al limite in pista, ma si rivolge alla
guida su strada di moto piuttosto pesanti. Comincia proprio con le basi
basiche, ma procede anche oltre i primi 1000 km :-)
Probabilmente un pilota esperto non ne ha bisogno, ma credo che non faccia
mai male leggere - o rileggere - anche la teoria di base, di solito capite
sempre che qualcosa ci sia sfuggito e ci sia quindi l'occasione per
rimetterlo in pratica :)
C.


 essere umano dotato di cervello impara nei primi 1000 km di moto. 
io di chilometri in moto ne ho fatti un centinaio e le ho imparate lo stesso
ste cose :)

Oh, non č che pensavo di postare la Bibbia, ho fatto solo un copia a 
incolla, se non serve come non detto :-) 

 altrimenti a che serve?
No, mettevo le mani avanti per evitare gli strali... :-) 

 incolla, se non serve come non detto :-)
nono serve serve...anzi grazie:-)
Ad esempio mi interessa la parte che riguarda la ripartizione tra la frenata
posteriore ed anteriore: se ho ben capito dice di frenare PRIMA con
l'anteriore e POI col posteriore...ok ma perché iniziare ad usare il freno
dietro quando il posteriore si è già alleggerito? Non si perde efficacia?
 
--
Fabio (SP-GE)
HONDA XL600V
TRANSALP '96
nero / grigio


 dietro quando il posteriore si è già alleggerito? Non si perde efficacia?
Essendo appena caduto per una frenata presumibilmente sbagliata, ritengo di
non essere l'interlocutore più qualificato per risponderti. Però a me sembra
di aver letto il contrario, non ricordo bene. Tieni presente che le moto dei
pulotti USA sono molto meno caricate davanti rispetto alle stradali jap, per
cui il posteriore ha sempre una certa aderenza, non si solleva mai, e quindi
puoi "frenarlo" maggiormente che non su un - 
p.es
. - CBR
Di più, nin zò :)
C.


 dietro quando il posteriore si è già alleggerito? Non si perde efficacia?
Freno posteriore? a che serve???
Ciao
Luca


Ciao!
--
Mko


 Il freno posteriore SERVE.
pienamente d'accordo.
--
Fabio (SP-GE)
HONDA XL600V
TRANSALP '96
nero / grigio


 means they lose most of their braking capability.
LOL...
Per la serie: 'si cresce "lattomobilisti" fin da piccoli' o in
alternativa 'ma 'n ce vediII?'.
Io stesso, prendendo a mano la moto dopo 5-6 anni di guida prima su 3 e
poi su 4 ruote, all'inizio involontariamente usavo il classico "pestone"
sul freno dietro, con il solo risultato di intraversarmi :-\ .
Poi ho visto che davanti c'e' sempre un disco bello grande... a volte ce
ne sono due, mentre dietro spesso c'e' poco piu' di un tamburo...
Boh, qualcosa vorra' dire ;-) .
-- 
Polentaro (BO) & "Ducati" NX 650 Dominator
Togli IL FONDELLO DELLO SCARICO per farti sentire in pvt.

 Boh, qualcosa vorra' dire ;-) .
Se leggi le altre risposte, e pensi a dei modelli non solo stradali (es. 
cancelli, enduro ecc.) ti accorgi che le cose cambiano, non c'entra l'essere 
automobilisti o meno
C. 

 c'entra l'essere automobilisti o meno
Minkia che legnata (cit.). Fortuna che ho la testa dura :-D .
mazz1) Non darmi dello stradale che mi offendo :-P .
mazz2) Per favore, non chiamarli "cancelli", sono moto anche quelle. ;-)
mazz3) Ho letto tutti dall'inizio alla fine (apposta ci ho messo quattro
giorni a rispondere :-P ; poi ero al CMRS, ma chissene), e ho trovato
molto interessante il tutto.
Non voleva essere un commento acido :-#°°, ma soltanto un'osservazione
scherzosa su atteggiamenti "atavici" o meglio, "da niubbi".
Poi, mi piace fare il luogo comune... anche solo per il gusto di
demolirlo in seguito :-D .
           <--Ritornando a bomba al post iniziale-->
Io stesso adeguo la frenata e la ripartizione del peso a seconda del
fondo (asfalto di ogni fatta, terra, ghiaia, pietre :-) ) e della
pendenza (salita o discesa cambia completamente il modo di guidare).
Abituato poi alla frenata di un dominator, che ha un comportamento
abbastanza diverso da una stradale:
  - forcella morbida (che se carichi troppo va a pacco uso ridere),
  - peso ripartito piu' sull'asse posteriore che sull'anteriore (tipico
dei mezzi impostati "alla fuoristradista"),
  - monodisco anteriore da 260mm ca. (ovvero: rallenta =:-O ),
  - ruota anteriore da 90 (per cui se strizzi troppo e non hai le gomme
giuste blocchi l'anteriore eppoisocca##i)...
Chi non sa come gestirla e non prende il giusto "margine" si incolla
alla prima curva (vedi risposta di Mko).
-- 
Polentaro.

 mazz2) Per favore, non chiamarli "cancelli", sono moto anche quelle. ;-)
Io ho una V-Rod, oltre a una mangia-riso ;-)
C. 

 Io ho una V-Rod, oltre a una mangia-riso ;-)
errare č umano, perseverare diabolico...
-- 
        Fahr' nie schneller als dein Schutzengel fliegen kann !
      Sandro & Duca 888 Sp4 "BARNSTORMER" 
IHM-...@yahoogroups.com
            Cavaliere per volere d'Iddio ed umano ardimento
                      Presidente del club PPCSP
         Gran Taroccatore del Villaggio del GFC membro #60 ;
                   ICQ:6891270; MSN msg: Red Flyer;
=======================================================================
Andiamo in moto-dissi scavalcando la sella-se succede qualcosa di buono
      per festeggiare, se succede qualcosa di cattivo per dimenticare
            se non succede niente...per far succedere qualcosa

 errare č umano, perseverare diabolico...
Mancavano le faccine o ce l'hai con me?


 Mancavano le faccine o ce l'hai con me?
lo vedi come sei ?  lo vedi come sei????
(cit. macario)
le faccine non le metto..
se parlo seriamente cambio firma
-- 
               Sandro & Duca 888 Sp4 "BARNSTORMER"
 
http://it.groups.yahoo.com/group/IHM-ROMA
         Cavaliere per volere d'Iddio ed umano ardimento
                    Presidente del club PPCSP
       Gran Taroccatore del Villaggio del GFC membro #60 ;
     ICQ:6891270; MSN msg: Red Flyer; Yahoo msg: red_flyer_1
================================================================
         "Noi siamo come il destino, chi va a star bene
                e chi va a prendersela nel culo"

 se parlo seriamente cambio firma
Quindi fin'ora hai usato sempre una sola firma... ;-)


>>>> La mia filosofia/pensiero tradotta in musica! <<<<<
N.B. I brani e/o i video non sono scaricabili, ma si potranno richiedere
gratuitamente scrivendo a me (l'indirizzo č sul sito)


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Ciao Fabrizio...
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Salve,

Distinti saluti
Alessandro S.
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--------------------------------
Inviato via 
http://arianna.libero.it/usenet/

>>>> La mia filosofia/pensiero tradotta in musica! <<<<<
N.B. I brani e/o i video non sono scaricabili, ma si potranno richiedere
gratuitamente scrivendo a me (l'indirizzo č sul sito)
