Correct Braking Proceedure

Bertie Wiggins said:

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.

I'd wager that you can't understand the elementary maths that proves you
wrong, or you wouldn't still be saying this.

James
--
James Annan
see web pages for email
http://www.ne.jp/asahi/julesandjames/home/
http://julesandjames.blogspot.com/

Tim Woodall said:

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

Bertie Wiggins cycling_remove_bertie@yahoo_dot_co_dot_uk said:

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.

I'm broadly with Bertie on this. I think the front brake only brigade
are forgetting that the objective is deceleration of bike and rider,
not just the bike. If all the weight is over the front wheel, they're
on the point of parting company.

Back wheel braking is demonstrably better with more weight over the
wheel. I show my trainees this by locking the back brake and trying to
drag a bike along with and without a rider.

I think the front brake is the more effective *because* the weight
tends to transfer to it. With the weight partly on the back wheel, the
rear brake can take more braking force before it skids, and the front
wheel less. Overall, with two contact points working instead of one,
you should stop quicker and under better control.

Colin McKenzie

"Saxman" <john.h.williams(removethis)@btinternet.com> wrote in message
news:[email hidden]...

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.

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.

If you haven't hit the brick wall yet, you're doing it right. Stop
worrying.

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

Quoted message said:

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.

Not read it, but I probably agree with what he writes. It's all common sense
when you have some experience.

However, I'm not sure he's written the unwritten rules....

"Skid the back wheel a little after ringing your bell 30 times".
"Come to a trackstand when it's useless people who have no idea of their
environment".
"Use your brakes when the car driver isn't looking at you".
"Always watch out for stupid dogs".[1]
[1] Watch out for their owners, they're generally just as stupid.

Anyway, that's my wiki addition!

Clive George said:

"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.

I agree. Also, I enjoy braking on the limit of the front wheel in the dry
at least, with the back wheel just thinking about lifting - well, at least
where it doesn't matter if I don't stop in exactly the right place. It's
kind of fun, like surfing for fat old lardies. :-)

Never come a cropper yet - I suspect I'm really a bit of a wimp and only
feel line I'm pushing it to the limit and it's not quite as funky as I'm
imagining it!

--
Nobby

"Saxman" <john.h.williams(removethis)@btinternet.com> wrote in message
news:[email hidden]...

Quoted message said:

On Tue, 25 Oct 2005 18:14:02 +0100, Saxman wrote:
Interesting comments from you all. I was told many years ago to use both
brakes, but apply to front brake first.

Always hit front brake first. Unless you are on a loose surface. Off road
you will generally be on the marbles. Watch out for the "face plant".

On road ... you should be covering your brakes at all times. In emergencies
hit the front first. Skidding does no slowing down in real terms.

Just keep controlled. Practice your emergency stops on gravel. You'll learn
quick then.

Nick

Pete Biggs said:

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.

As described. Done it with a recumbent, but with the geometry of mine,
it was possible to lift the rear wheel before losing traction at the front.

Quoted message said:

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.

I have been riding the fixie and the Giant recently. The former has no
rear brake (My legs aren't strong enough to resist the 72" gear!) and
the rear on the Giant has not been used, despite near continuous rain.
Looking out for diesel slicks and the little metal cones they use to
mark pedestrian crossings has prevented a loss of front wheel traction.

On the Giant, I currently go through front brake pads at least twice as
fast as rear ones.

Jon

elyob said:

On road ... you should be covering your brakes at all times. In emergencies
hit the front first. Skidding does no slowing down in real terms.

I disagree. You should be covering your brakes if there is a potential
hazard. On an open road, with clear sightlines, you do not need to be
hovering over the levers. During a rapid sprint past a moving vehicle in
multi-lane city traffic... it might be a good idea.

Jon

James Annan said:

Bertie Wiggins said:

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.

I'd wager that you can't understand the elementary maths that proves you
wrong, or you wouldn't still be saying this.

I agree that my meaning in the above was ambiguous. I have already
corrected myself.

Lets look at where the energy goes under braking. A small amount will
be lost as sound, considerably more will be lost as heat. Four
contact points (2 front and 2 rear) can lose heat energy more
effectively than just two points (2 front or 2 rear). This suggests
that breaking with both brakes will be more efficient than front
brakes only.

Colin McKenzie said:

Tim Woodall said:

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

Bertie Wiggins cycling_remove_bertie@yahoo_dot_co_dot_uk said:

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.

I'm broadly with Bertie on this. I think the front brake only brigade
are forgetting that the objective is deceleration of bike and rider,
not just the bike. If all the weight is over the front wheel, they're
on the point of parting company.

Back wheel braking is demonstrably better with more weight over the
wheel. I show my trainees this by locking the back brake and trying to
drag a bike along with and without a rider.

I think the front brake is the more effective *because* the weight
tends to transfer to it. With the weight partly on the back wheel, the
rear brake can take more braking force before it skids, and the front
wheel less. Overall, with two contact points working instead of one,
you should stop quicker and under better control.

John Franklin in Cyclecraft (page 20) says the following: "If you need
to brake at all quickly, you need to apply both brakes. For maximum
efficiency and safety, 75% of the braking power should be applied to
the front brake and 25% to the rear on a firm, dry road. In the wet,
it is important to modify this to 50:50. Practise applying the rear
brake a fration of a second before the front until this becomes second
nature every time. As far as possible, only brake when steering
straight."

I've no idea where he gets the 75:25 figure from. It suggests to me
that the rider's mass should be positioned so that under maximum
braking 75% of the weight is on the front wheel and 25% on the rear.
In lighter braking in the wet the rider's mass should be positioned so
that the weight distribution is closer to 50% front and 50% rear. I
can only think that the rider's mass in the dry would have to be so
far back to achieve a weight distribution under maximum braking of 50%
front and 50% rear to be impractical.

Bertie Wiggins said:

John Franklin in Cyclecraft (page 20) says the following: "If you need
to brake at all quickly, you need to apply both brakes. For maximum
efficiency and safety, 75% of the braking power should be applied to
the front brake and 25% to the rear on a firm, dry road. In the wet,
it is important to modify this to 50:50. Practise applying the rear
brake a fration of a second before the front until this becomes second
nature every time. As far as possible, only brake when steering
straight."

I've no idea where he gets the 75:25 figure from.

It's a made-up compromise, which is a fairly reasonable all-purpose
alternative to braking absolutely correctly for the individual
circumstance. In other words, it's something that's easy to teach and
learn, but isn't actually the best thing everyone can do every time.

~PB

"Bertie Wiggins" <cycling_remove_bertie@yahoo_dot_co_dot_uk> wrote in
message news:[email hidden]...

Quoted message said:

I've no idea where he gets the 75:25 figure from. It suggests to me
that the rider's mass should be positioned so that under maximum
braking 75% of the weight is on the front wheel and 25% on the rear.

What if it's not possible to position the rider's weight there? Under
properly heavy braking on an upright bike, the rider's weight on the rear
wheel is about zero. And that's even if you're trying.

Are you arguing that the design of the bike should be changed, or are you
trying to work within the limitations provided by conventional bicycle
technology?

cheers,
clive

Colin McKenzie said:

I'm broadly with Bertie on this. I think the front brake only brigade
are forgetting that the objective is deceleration of bike and rider,
not just the bike. If all the weight is over the front wheel, they're
on the point of parting company.

You need to be at that point where the rear wheel is just about to rise
(or does rise a little) if you want to brake as hard as possible (where
traction isn't an issue) because that's what deceleration causes. Just
before that point there is hardly any weight over the rear so there is
hardly any point in using the rear brake. A cyclist with the skill can
handle that point. Anyone without the skill should practise to learn it
because it is a life saver. You don't go over the bars or fall off the
bike if you know what to expect and react to what's happening

Quoted message said:

Back wheel braking is demonstrably better with more weight over the
wheel. I show my trainees this by locking the back brake and trying to
drag a bike along with and without a rider.

I think the front brake is the more effective *because* the weight
tends to transfer to it.

That's right but there's only a limited amount you can do against it.

Quoted message said:

With the weight partly on the back wheel, the
rear brake can take more braking force before it skids, and the front
wheel less. Overall, with two contact points working instead of one,
you should stop quicker and under better control.

You dont stop quicker (where traction isn't an issue). It's normally not
possible to get enough weight on the back to make it effective during
maximum braking unless the front brake (or rider) is weak.

~PB

Bertie Wiggins said:

James Annan said:

Bertie Wiggins said:

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.

I'd wager that you can't understand the elementary maths that proves you
wrong, or you wouldn't still be saying this.

I agree that my meaning in the above was ambiguous. I have already
corrected myself.

Lets look at where the energy goes under braking. A small amount will
be lost as sound, considerably more will be lost as heat. Four
contact points (2 front and 2 rear) can lose heat energy more
effectively than just two points (2 front or 2 rear). This suggests
that breaking with both brakes will be more efficient than front
brakes only.

Energy dissipation is not an issue, except in special circumstances
such as a sustained braking on a long steep descent (and even in that
case, front braking alone will give the strongest deceleration).

I repeat: it is a matter of elementary geometry and mechanics. If you
can't do it, stop pretending that you know better than those of us who
can!

James

In message <[email hidden]>

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.

Personally I use both brakes approx equally. If I do an emergancy stop it
is both brakes hard. If I decelerate slowly, I use the rear. If I stop
for quickly for lights I mainly use the front, and use the rear for fine
control.

You should regualary use both brakes to their full power to make sure they
are working properly. About ten years ago I main used the rear brake, this
failed on the way to uni. Using my then seldom used front brake, it
snapped a minute after.

Martin.

--
According to the human genome project, humans are 50-60% bananas.
When emailing me, please include the word Banana in the subject line.

elyob said:

On road ... you should be covering your brakes at all times.

Nonsense. Who rides in a way where there is never a second to spare for
moving a hand to the brake lever? Cyclists who slipstream inches behind a
vehicle everywhere? Any cyclist who needs that 0.5 to 1 second *all the
time* is no good, frankly. It's not even necessary to continuously cover
the brakes in rush-hour central London.

The way to do it is give yourself plenty of reaction time and
stopping/avoidance distance, from dangers from the sides as well as in
front. For instance, don't ride anywhere near the kerb where there are
pedestrians close to edge of pavement.

~PB

Clive George said:

Quoted message said:

I've no idea where he gets the 75:25 figure from. It suggests to me
that the rider's mass should be positioned so that under maximum
braking 75% of the weight is on the front wheel and 25% on the rear.

What if it's not possible to position the rider's weight there? Under
properly heavy braking on an upright bike, the rider's weight on the rear
wheel is about zero. And that's even if you're trying.

It seems dangerous to teach people to brake so heavily that the rear
wheel is on the point of getting airborne. It also seems inefficient
to dissipate energy through 2 brake blocks instead of 4.

Quoted message said:

Are you arguing that the design of the bike should be changed, or are you
trying to work within the limitations provided by conventional bicycle
technology?

I'm trying to argue the case for the most effective braking.

James Annan said:

I repeat: it is a matter of elementary geometry and mechanics. If you
can't do it, stop pretending that you know better than those of us who
can!

I am not so arrogant as to insist that I am correct; I am not so
conceited as to claim superior mathematical, geometric or mechanical
knowledge. However, I am not going to accept, on your word, that
applying the front brake alone is more effective than applying front
and rear brake together. As the geometry and mechanics is so
"elementary" you may provide a mathematical model to support your
claim, if I cannot follow the "elementary" mathematics I am sure
others can.

It seems to me that the most effective theoretical braking is when the
cyclist adjusts their mass so there is equal weight on both wheels so
as much tyre is in contact with the ground as possible, the brakes are
applied with a force at a point before a skid, so the turning of the
two wheels are being slowed at maximum rate without locking.

You are clearly right that maximum braking of the front wheel is when
all the cyclist's weight is on the front wheel. It is also right that
maximum braking on the rear wheel is when all the weight is over the
rear wheel. I argue that maximum braking overall is when neither
wheel has reached its maximum braking potential, but at some other
point. Franklin suggests 75:25. I don't understand why 50:50 would
not be the give the greatest overall braking - but I do accept your
point that there are limitations to how a real cyclist can adjust
their mass.

Bertie Wiggins said:

James Annan said:

I repeat: it is a matter of elementary geometry and mechanics. If you
can't do it, stop pretending that you know better than those of us who
can!

I am not so arrogant as to insist that I am correct; I am not so
conceited as to claim superior mathematical, geometric or mechanical
knowledge. However, I am not going to accept, on your word, that
applying the front brake alone is more effective than applying front
and rear brake together. As the geometry and mechanics is so
"elementary" you may provide a mathematical model to support your
claim, if I cannot follow the "elementary" mathematics I am sure
others can.

Ok, here is a simple version.

If you slow down too fast, you'll go over the handlebars. For a normal
riding position, the limiting deceleration is about 0.6g (and you can't
do a great deal about shifting your CofG). That corresponds to a CofG
that is at an angle of about 30 degrees behind vertical, above and
behind the front wheel's contact point with the ground.

So, once you are braking at this theoretical limit of 0.6g, there is no
weight on the back wheel. Say you want to be a bit more conservative,
and only brake at 0.5g. In this case, you'll have about 9/10 of your
weight on the back wheel and 1/10 on the front (can't be bothered doing
the sums properly). Since the coefficient of friction is unlikely to be
significantly above 1, this limits the braking on the rear wheel to
0.1g at best, ie 20% of your total. Energy dissipation simply doesn't
come into it.

Forrester's 75%/25% is not too unreasonable in practice, especially
given that a rear wheel skid is rarely fatal and generally easy to
recover from. Attempting a ratio of 50%/50% will substantially limit
the deceleration you can achieve, because the rear wheel will start to
skid as your effective weight distribution changes under moderate
braking.

James

Bertie Wiggins said:

Clive George said:

Quoted message said:

I've no idea where he gets the 75:25 figure from. It suggests to me
that the rider's mass should be positioned so that under maximum
braking 75% of the weight is on the front wheel and 25% on the rear.

What if it's not possible to position the rider's weight there? Under
properly heavy braking on an upright bike, the rider's weight on the rear
wheel is about zero. And that's even if you're trying.

It seems dangerous to teach people to brake so heavily that the rear
wheel is on the point of getting airborne. It also seems inefficient
to dissipate energy through 2 brake blocks instead of 4.

Errrmm, but the rear wheel is still tracking, not skidding, unless of
course you use the rear brake. Ineficient it may, but you have loads
spare so don't worry.

Horses for courses, use whatever you feel happy with, if you take an SUV
up the chuff, try out some empirical experiments.

<snip>