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Thoughts on braking



 
 
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  #1  
Old August 1st 03, 07:31 PM
John Appleby
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Default Thoughts on braking

3) If trail riders don't use their front brakes much--as my friend,
who was a sometime MTBer, seems to allege--why do I see so many
front-wheel disk brakes?


If you think of your weight distribution on the bike, the rear wheel can
lock and you can carry on slowing down, whilst if the front wheel locks you
are over the bars.

As a result the front brake is far more effective a stopping mechanism
provided you don't lock it up. Obviously using both brakes at once is going
to stop you faster than using just one, though I suspect that in average MTB
riding use, you use mostly the front brake when braking hard. 70% sounds
realistic.

What is often the case on a MTB is that you use the rear brake for tactical
manoevres - for example to control your line of attack in a sharp corner.
Try doing that with the front brake and you will find that it slides
underneath you and you stack.

My suspicion is that either your friend hasn't ridden without a front brake,
or he doesn't ride very hard.

Regards,

John


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  #2  
Old August 1st 03, 07:40 PM
Rick Onanian
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Default Thoughts on braking

On 1 Aug 2003 10:35:16 -0700, Luigi de Guzman wrote:
2) Is there some sort of maximum speed, or some other purely physical
limit to front-brake only braking? Why do the motorcycle guys
recommend two-brake braking? [this will probably require me to do


I suspect that the additional weight and weight distribution of
motorcycles makes the rear brake more useful. Additionally, it
could well be law in some states that motorcyclists must use both.

On top of all that, the nature of motorcycles AFAIK is that they
just don't require as much technique, though it certainly seems
that they _would_.

3) If trail riders don't use their front brakes much--as my friend,
who was a sometime MTBer, seems to allege--why do I see so many
front-wheel disk brakes?


How the hell does he get any braking accomplished on loose dirt
and mud and rocks and whatever else, using only the rear brake?

Aside from not being able to control his bike, he must tear up
the trails to no end.

I rarely use my rear brake; but my reflexes don't forget it in
a panic stop, either, whether on my road bike or my MTB.

-Luigi

--
Rick Onanian
  #3  
Old August 1st 03, 07:40 PM
asqui
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Default Thoughts on braking

Luigi de Guzman wrote:
[....]
Both brakes should be applied at the same time when stopping. Even
though the full braking potential of each wheel may not be required
for normal, planned stops, it is important to develop the habit of
using both brakes so that your reflexes will be ready to respond
quickly and properly when an emergency situation occurs."

they even have a diagram:

http://www.msf-usa.org/CourseReview/assets/RiderHandbook_27_1.gif

[...]

Oh dear, not more of this nonsense.

Disclamer: The following discussion is carried out in the context of braking
on regular, clean, dry, level, road surface in a straight line, for the
purpose of decelerating from a given velocity to zero velocity in the
shortest distance possible.

Assuming the front tyre has enough traction to not skid before the
pitch-over point (reasonable assumption IMO). Maximal braking is at the
pitch-over point where your rear wheel is just about to leave the ground,
and cannot possibly contribute any significant amount of braking.

Hence at max. braking your rear brake contributes little more than a
skidding rear wheel, helping you on your way to losing control.

Dani


  #4  
Old August 1st 03, 09:05 PM
Eric Murray
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Default Thoughts on braking

In article ,
Luigi de Guzman wrote:

[front brake]

Then, out of curiosity, I went to see what our fossil-fueled brothers
on motorbikes have to say about braking. They say to brake with both
at the same time:


[quote from MSF]

1) Those big Flying Pigeons or Dutch roadsters, with only coaster
brakes, were probably never intended to go very fast at all. My
braking distance with only a rear coaster was scary, and my ability to
brake depended largely on where my feet were in the pedal stroke.
unnerving. [and I'm not very fast--the messengers and a lot of
commuters, indeed, at at least one little girl can all beat me,
speedwise]


Early motorcycles had only one brake, the rear, as well.


2) Is there some sort of maximum speed, or some other purely physical
limit to front-brake only braking?


Yes, the point at which you flip the bike over forwards.

Why do the motorcycle guys
recommend two-brake braking?


This is the MSF you are quoting. They are there to teach
beginning riders how to ride. Beginning riders, and riders who
learned improperly, are like your friend: they are afraid of
the front brake. There is even an old myth among motorcyclists
that the front brake will "flip you right over".
But on a motorcycle the front brake is
even more important than it is on a bicycle.

Motorcycle road racers often use only the front brake. Most of
those that use the rear use it more for suspension-related
reasons that are not applicable to bicycles and are too complicated
to explain.

A good motorcycle road racer will, at the point of maximum braking into
an approaching corner, have essentially zero weight on the rear.
Gary Nixon was famous for having his rear wheel in the air
on the approach to every corner.

3) If trail riders don't use their front brakes much--as my friend,
who was a sometime MTBer, seems to allege--why do I see so many
front-wheel disk brakes?


Your friend is wrong. Front brakes are important for
off-road riding as well.


Eric


  #5  
Old August 1st 03, 09:54 PM
Paul Bielec
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Default Thoughts on braking

I have a MTB.
When on pavement, I use both brakes but mostly the rear brake when on flat
and not going to fast. When going faster, the rear brake alone is not
enough. It will block because the weigt gets transfered to the front. Once
the rear is blocked, the rear brake is not that efficient anymore.
When on a Cross Country trail, you have to use both brakes when you go down.
The slopes are much stiffer than on the street or bike path. In addition,
the ground (soil, sand, mud, rocks etc) provides far less traction than
pavement. It is very easy to block your rear wheel in which case it makes
the rear brake even more inefficient than on pavement. So the trick is to
use the front brake as much as you can without blocking the front wheel
which would result in a nice dive over the handle bars with good chances of
having the bike landing on top of you.
Also, you'd try to transfer your weight to the rear and low by moving a
little behind your saddle.
MTB without front brake...never.
The disc brakes, in addition of having a better braking power, don't get
dirty as easy as the rims do. When you ride through several inches of mud
and water, it takes some time before the rims clean up.


  #6  
Old August 1st 03, 10:07 PM
Rick Onanian
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Default Thoughts on braking

On Fri, 1 Aug 2003 16:54:59 -0400, Paul Bielec wrote:
The disc brakes, in addition of having a better braking power, don't get
dirty as easy as the rims do. When you ride through several inches of mud
and water, it takes some time before the rims clean up.


....and if your rims are the least bit out of true, or if your
brakes are adjusted very close, then you get terrible, horrible
scraping noises (while not applying the brake) which are so
loud they are not only embarassing but distracting too.

That's the main reason I'd like disc brakes for my MTB; I like
to keep my V brakes adjusted very close, but they sure get loud
when the rim gets muddy.

--
Rick Onanian
  #7  
Old August 1st 03, 11:05 PM
Todd Kuzma
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Default Thoughts on braking

Luigi de Guzman wrote:

1) Those big Flying Pigeons or Dutch roadsters, with only coaster
brakes,


Not sure about the Dutch, but the Flying Pigeons have no
coaster brakes. They use rod-operated brakes which are next
to useless.

Todd Kuzma

  #8  
Old August 1st 03, 11:12 PM
Eric Murray
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Default Thoughts on braking

In article ,
Rick Onanian wrote:
On 1 Aug 2003 10:35:16 -0700, Luigi de Guzman wrote:
2) Is there some sort of maximum speed, or some other purely physical
limit to front-brake only braking? Why do the motorcycle guys
recommend two-brake braking? [this will probably require me to do


I suspect that the additional weight and weight distribution of
motorcycles makes the rear brake more useful.


It depends on the motorcycle. Long low Harleys put more
weight on the rear wheel than short sport bikes.

Additionally, it
could well be law in some states that motorcyclists must use both.


It could be, but it's not.
Most states do require front and rear brakes on bikes older
than a certain age, but there's no laws about using them.

On top of all that, the nature of motorcycles AFAIK is that they
just don't require as much technique, though it certainly seems
that they _would_.


They require more skill in order to go fast.
A strong bicyclist can be fast even with poor technique..
whatever they lose on technical descents they make up into the wind
or up hills. With motorcycles, unless we are talking
straight line speed, it's all up to the skill of the rider.

Of course there are lots of motorcyclists who are the equivalent
of bicyclists who tootle along the bike path on a sunday.


Eric

  #9  
Old August 1st 03, 11:28 PM
Luigi de Guzman
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Default Thoughts on braking

"asqui" wrote in message ...
Luigi de Guzman wrote:
[....]
Both brakes should be applied at the same time when stopping. Even
though the full braking potential of each wheel may not be required
for normal, planned stops, it is important to develop the habit of
using both brakes so that your reflexes will be ready to respond
quickly and properly when an emergency situation occurs."

they even have a diagram:

http://www.msf-usa.org/CourseReview/assets/RiderHandbook_27_1.gif

[...]

Oh dear, not more of this nonsense.

Disclamer: The following discussion is carried out in the context of braking
on regular, clean, dry, level, road surface in a straight line, for the
purpose of decelerating from a given velocity to zero velocity in the
shortest distance possible.

Assuming the front tyre has enough traction to not skid before the
pitch-over point (reasonable assumption IMO). Maximal braking is at the
pitch-over point where your rear wheel is just about to leave the ground,
and cannot possibly contribute any significant amount of braking.

Hence at max. braking your rear brake contributes little more than a
skidding rear wheel, helping you on your way to losing control.

Dani


I'm not disputing your statement. what I'm asking is--if front-wheel
only braking is maximal, why do the motorcycle guys say to use both
brakes? Especially considering their maximum speeds are much higher
than ours...

It looks like I'm going to have to perform experiments.

-Luigi
  #10  
Old August 2nd 03, 12:03 AM
S. Anderson
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Default Thoughts on braking

"Luigi de Guzman" wrote in message
om...
"asqui" wrote in message

...

I'm not disputing your statement. what I'm asking is--if front-wheel
only braking is maximal, why do the motorcycle guys say to use both
brakes? Especially considering their maximum speeds are much higher
than ours...

It looks like I'm going to have to perform experiments.

-Luigi


I'm a motorcycle guy and I'm telling you I rarely use the rear brake. When
I'm braking heavily the rear wheel will actually be in the air part of the
time. The rear brake does very little at maximum braking, other than give
you something else to worry about. At more moderate stopping pressures the
rear brake can contribute to braking proportionate to the weight that's on
the rear tire. At the racetrack I never touch the rear brake. On the
street, I use it occasionally when it's wet out and to hold my bike still at
stop lights..that's about it.

Cheers,

Scott..


 




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