Correct Braking Proceedure

Quoted message said:

This has probably been discussed before, but I would like to know.

It has, extensively.

Have a look at http://sheldonbrown.com/brakturn.html

For all that you probably need.

Following on from Saxman's message. . .

Quoted message said:

I have to admit that after many years I really do not know how to use my
brakes correctly on my bike. One tends to do these things by instinct.

An ounce of practice is worth a ton of theory so experiment.

--
PETER FOX Not the same since the poster business went to the wall
[email hidden]
2 Tees Close, Witham, Essex.
Gravity beer in Essex <http://www.eminent.demon.co.uk>

On Tue, 25 Oct 2005 18:14:02 +0100, Saxman

john.h.williams(removethis)@btinternet.com said:

I have to admit that after many years I really do not know how to use my
brakes correctly on my bike. One tends to do these things by instinct.

Should one use the front brake first followed by the rear brake or the
reverse? Should they be applied simultaneously? Maybe it depends on what
gradient one is on? It might be down to which brake performs better?

This has probably been discussed before, but I would like to know.

Sheldon Brown suggests that front brake alone is correct in nearly all
braking situations.

I disagree with Sheldon Brown, but it is worth reading what he says.

http://sheldonbrown.com/brakturn.html

Sheldon argues that maximum braking force is at the point when the
rear wheel is about to lift from the ground, and the rear wheel has no
traction, therefore applying the rear brake has no effect, thus for
maximum braking the front brake is all that is required in most
situations.

Here's what I say...

Braking with both brakes is more effective because the braking force
is by slowing both wheels by pushing the pads onto the rims, and
neither brake need be fully applied to slow the bike as fast as
applying the front brake alone. Applying the rear brake too hard can
cause the rear wheel to lock, possibly causing the bike to slew.
Applying the front brake too hard can cause the front wheel to lock,
possibly causing the rear end to lift, or front wheel to skid.

To prevent a rear wheel skid, don't apply the rear brake too hard.

To lessen the chance of a rear end lift, shift your weight back.

A front wheel skid is rare on tarmac.

To brake quickly on tarmac, shift your weight back by locking your
arms, apply both brakes, with more pressure on the front brake. On
steep decents, pump your brakes to lessen the chance of the rims over
heating which can cause a blow out.

Bertie Wiggins said:

Here's what I say...

Braking with both brakes is more effective because the braking force
is by slowing both wheels by pushing the pads onto the rims, and
neither brake need be fully applied to slow the bike as fast as
applying the front brake alone.

But that will not slow the bike as fast as the front brake alone purely
because the geometry means that the maximum deceleration you can achieve
will have transferred all the weight to the front wheel only.

--
Tony

"I did make a mistake once - I thought I'd made a mistake but I hadn't"
Anon

Tony Raven said:

Bertie Wiggins said:

Here's what I say...

Braking with both brakes is more effective because the braking force
is by slowing both wheels by pushing the pads onto the rims, and
neither brake need be fully applied to slow the bike as fast as
applying the front brake alone.

But that will not slow the bike as fast as the front brake alone purely
because the geometry means that the maximum deceleration you can achieve
will have transferred all the weight to the front wheel only.

That ignores the possibility that the limit of braking may be the tyres
skidding rather than lifting a wheel or the brakes themselves.

In my personal instance of riding a recumbent bike a lot of the time
it's virtually impossible to lift the back wheel under braking and the
disc brakes are capable of locking either wheel at will. On an upright
with it's attendant high CoG Sheldon is right a lot more of the time but
this is still not the case on icy, wet, leafy or greasy roads.

In the dry I use the front brake alone, SB is quite correcect in this
situation.

In the wet I use both brakes, biased toward the front and gradually
increase braking force until the back starts to lock up, this gives me a
good indicator of how much grip I've got at the front without
encountering the much less controllable front wheel skid.

Alex

Tony Raven said:

Bertie Wiggins said:

Here's what I say...

Braking with both brakes is more effective because the braking force
is by slowing both wheels by pushing the pads onto the rims, and
neither brake need be fully applied to slow the bike as fast as
applying the front brake alone.

But that will not slow the bike as fast as the front brake alone purely
because the geometry means that the maximum deceleration you can achieve
will have transferred all the weight to the front wheel only.

I know I'm going to regret this but...This assumes the gometry of the
bike is sufficient to allow the rear wheel to lift. If this is not the
case the front will lock and the back can be used to decrease the
stopping distance.

So, the question is, is it impossible to lift the rear wheel before
losing traction for some bikes?

What about wet road surface?

For my tuppence worth, for me, it's front brake only. The rear is only
used to impress 16yo girlies at bus stops.

Without doubt the front is capable of retarding the bike quickest. If the wheel feels like it will lock and the rear hasn't lifted then there will be some braking potential from the rear but not a great deal due to the weight transfer. I think we all agree on this.

Personally I only use the rear. I do this because it is good practice for judging braking distances and feeling grip and I always know that if I make a mistake I will have a really powerful front brake to get me out of trouble.

"MichaelB" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Without doubt the front is capable of retarding the bike quickest. If
the wheel feels like it will lock and the rear hasn't lifted then there
will be some braking potential from the rear but not a great deal due to
the weight transfer. I think we all agree on this.

Personally I only use the rear. I do this because it is good practice
for judging braking distances and feeling grip and I always know that
if I make a mistake I will have a really powerful front brake to get me
out of trouble.

You probably ought to keep in practice using the front, otherwise when you
apply it for the emergency it could all go horribly wrong.

(Not at all convinced by your 'judging braking distances' argument - in what
way will just using the rear brake tell you your braking distance?)

cheers,
clive

Bertie Wiggins said:

Sheldon Brown suggests that front brake alone is correct in nearly all
braking situations.

I disagree with Sheldon Brown, but it is worth reading what he says.

I hardly ever use my rear brake. In fact, I went out on a longish club
ride a couple of weeks ago and didn't even notice that I had forgotten
to refit the rear brake blocks (after a spot of tinkering) until one of
my riding companions pointed it out to me...

All I can say is thank god my front brakes didn't fail on a descent.
That would not have been a very nice way to discover the lack of rear brake.

Quoted message said:

To prevent a rear wheel skid, don't apply the rear brake too hard.

Or just brake /before/ you start turning and let off the brakes during
the turn.

Quoted message said:

A front wheel skid is rare on tarmac.

....unless it's wet, when it becomes all too easy to make the front wheel
skid.

d.

On Tue, 25 Oct 2005 19:05:14 +0100, Tony Raven <[email hidden]>

Quoted message said:

But that will not slow the bike as fast as the front brake alone purely
because the geometry means that the maximum deceleration you can achieve
will have transferred all the weight to the front wheel only.

Then shift your weight back and use the back brake too.

I'd like to see a mathematical equation where deceleration is a
component of front braking, front wheel friction with tarmac, rear
braking and rear wheel friction with tarmac.

I'd wager that greatest deceleration is when front wheel friction with
tarmac = rear wheel friction with tarmac and front braking = rear
braking. This implies that weight should be distributed so that under
braking there is an even weight distribution.

Bertie Wiggins said:

http://sheldonbrown.com/brakturn.html

Sheldon argues that maximum braking force is at the point when the
rear wheel is about to lift from the ground, and the rear wheel has no
traction, therefore applying the rear brake has no effect, thus for
maximum braking the front brake is all that is required in most
situations.

Here's what I say...

Braking with both brakes is more effective because the braking force
is by slowing both wheels by pushing the pads onto the rims, and
neither brake need be fully applied to slow the bike as fast as
applying the front brake alone.

You can't maximum-brake like that. The front brake does need to be fully
applied for maximum braking. In terms of sheer stopping power, no amount
of rear braking makes up for any lack of front braking force on an upright
bike, unless there is an abnormally heavy weight on the back -- and more
than could normally be achieved by shifting body weight (by a non stunt
rider with a non funny bike).

Quoted message said:

Applying the rear brake too hard can
cause the rear wheel to lock, possibly causing the bike to slew.
Applying the front brake too hard can cause the front wheel to lock,
possibly causing the rear end to lift, or front wheel to skid.

It is not the front wheel locking that causes the rear end to lift, but
the sudden deceleration itself. In fact the rear wheel will start to rise
before the front wheel has stopped turning -- long before, when braking
from high speed. The wheel will still be slipping past the brakes.

But you do need sudden decleration if you want to stop or slow quickly, so
use of the rear brake won't then help keep the rear wheel on the ground.
When braking hard, all you can do to prevent an "endo" is brace against
the handlebars and keep your weight far back as possible, within reason.
Also be ready to release the front brake if you do go up in the air too
high and re-apply when you come back down, and so on.

The rear brake may be sensible to use on (potentially) slippery surfaces
but it will not prevent the rear end rising. There, all you can hope for
is that there is enough stopping distance to allow you to brake gently.

Of course the rear won't rise when braking gently with whatever brake(s)
you use. So moderate braking with the front alone is not dangerous when
there is little chance of a front-skid. Hard braking is potentially
dangerous but then slamming into something because you can't stop in time
is also just a bit dangerous!

~PB

Bertie Wiggins said:

I'd like to see a mathematical equation where deceleration is a component
of front braking, front wheel friction with tarmac, rear braking and rear
wheel friction with tarmac.

Wheelbase and height of Centre-of-Gravity also come into it. Which is why
tandems & 'bents have somewhat different behaviour under braking to
upright singles. I'll dig out the solution tomorrow morning (if anyone
still cares by then).

Quoted message said:

This implies that weight should be distributed so that under braking
there is an even weight distribution.

Nope, you want the "weight" as far back and as low as possible.

All this is covered in "Bicycling Science" by David Wilson, which you may
find very interesting, if difficult to put over to your pupils.

Mike

Tosspot said:

So, the question is, is it impossible to lift the rear wheel before
losing traction for some bikes?

It's virtually impossible to loose front traction on a non-recumbent bike
on good clean tarmac, in a straight line at least, unless perhaps using
extremely sub-standard tyres.

Quoted message said:

What about wet road surface?

Still difficult to skid the front tyre unless going round a bend or if
there is something like oil, gravel or ice mixed with the water.

~PB

On Tue, 25 Oct 2005 20:43:04 +0100,

Bertie Wiggins cycling_remove_bertie@yahoo_dot_co_dot_uk said:

On Tue, 25 Oct 2005 19:05:14 +0100, Tony Raven <[email hidden]>

Quoted message said:

But that will not slow the bike as fast as the front brake alone purely
because the geometry means that the maximum deceleration you can achieve
will have transferred all the weight to the front wheel only.

Then shift your weight back and use the back brake too.

I'd like to see a mathematical equation where deceleration is a
component of front braking, front wheel friction with tarmac, rear
braking and rear wheel friction with tarmac.

I'd wager that greatest deceleration is when front wheel friction with
tarmac = rear wheel friction with tarmac and front braking = rear
braking. This implies that weight should be distributed so that under
braking there is an even weight distribution.

No. If the CoG is above the front axle and assuming the front wheel
doesn't skid[1] then maximum braking will occur when the back wheel lifts.
Shifting your weight back will give more braking on the front wheel
before the rear wheel lifts but maximum braking will still occur on the
front wheel only.

Tim.

[1] And assuming that CoF doesn't change significantly with change in
size of contact patch.
--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t,"
and there was light.

http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/

Mike Causer said:

Bertie Wiggins said:

I'd like to see a mathematical equation where deceleration is a component
of front braking, front wheel friction with tarmac, rear braking and rear
wheel friction with tarmac.

Wheelbase and height of Centre-of-Gravity also come into it.

I'm sure they do, but only as a component of wheel friction with
tarmac.

Quoted message said:

Which is why
tandems & 'bents have somewhat different behaviour under braking to
upright singles. I'll dig out the solution tomorrow morning (if anyone
still cares by then).

Quoted message said:

This implies that weight should be distributed so that under braking
there is an even weight distribution.

Nope, you want the "weight" as far back and as low as possible.

I'll rephrase as I was ambiguous in what I meant above.

This implies that weight should be distributed so that under braking
there is an even frictional force between both wheels and the tarmac.

Quoted message said:

All this is covered in "Bicycling Science" by David Wilson, which you may
find very interesting, if difficult to put over to your pupils.

At primary age children tend to accept what their teachers say without
demanding formal proof.

Mr Tickle said:

Then shift your weight back and use the back brake too.

There's a limit to how far back you can shift it and still reach the bars.
That limit isn't enough in most cases.

~PB

Tim Woodall said:

No. If the CoG is above the front axle and assuming the front wheel
doesn't skid[1]

And why the front axle rather than the contact patch? Given a
sufficient degree of friction, any bike will endo if the point about
which it turns (the contact patch) is below the CoG. Which is always
the case on a level road, and ony not the case when falling over
backwards climbing a very steep hill.

...d (who tends to use both brakes to scrub speed, and has only had to
'drop anchors' hard enough to lift the rear wheel off the ground once
in the last few years (and that was going uphill too! )

MichaelB said:

Personally I only use the rear.

Likewise, mostly because my previous bike was a BMX with pedal-back
(i.e. pedal backwards and immediately lock the back wheel - and get
through a few tyres ! ;-) and I have locked the front and come off on
the bike before that one. Even now I'm hesitant about using too much
front brake to the point where I've avoided it completely so far on
this one.

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Saxman said:

I have to admit that after many years I really do not know how to use my
brakes correctly on my bike. One tends to do these things by instinct.

Should one use the front brake first followed by the rear brake or the
reverse? Should they be applied simultaneously? Maybe it depends on what
gradient one is on? It might be down to which brake performs better?

This has probably been discussed before, but I would like to know.

Interesting comments from you all. I was told many years ago to use both
brakes, but apply to front brake first.