Cycling UK Forum

hubgearfreak wrote:it is pointless to try and prove or disprove it. you can't do what sheldon's theory says, because you can't override years of learnt experience and risk smashing your face into the road.

Yes you most certainly can.

I do sometimes move my weight forward for the fun of it. When braking with both brakes and the weight back I stand on the pedals and move forward so that my body is in as best I can in line over the bottom bracket.
The rear wheel locks first then almost immediately lifts and the bike accelerates. It is good fun to try and balance the bike with the rear wheel off the floor and a tight corner coming up.

But how do we get R2 (Reohn2) to slow our bikes down?

mark a. wrote:Excellent post, Andrew. Thanks!

+1 for that!
I would say that COG should be further back. Perhaps as far back as the saddle mount. Of course it varies from bike to bike and rider to rider, but further back anyway.
You make no allowance for the COG being moved rearwards during ES.

hubgearfreak wrote:it is pointless to try and prove or disprove it. you can't do what sheldon's theory says, because you can't override years of learnt experience and risk smashing your face into the road. as andrew's excellent diagrams (nice work andrew ) show above, sheldon is right, in theory - but none of us have the recklessness to be able to get there, as mark & i have said.

SB is correct. I've always said that.
My point about his statement is that it's not complete. He has no statement about speed or weight. I keep saying this. He is correct, but not fully correct.

The front brake takes a finite time to get to max braking, so the rear brake has good use.
The COG can be shifted rearwards in an ES situation to keep the weight at the back. I do this naturally and automatically.

SB says that you MUST NOT use your rear brake in an ES situation. Why not? Even if it has no effect, does it matter?

I say it does have an effect so you MUST use it. This is not born out of a lifetime of cycling, it is born out of living in the Real World.

PS:
As a car diver - as I'm sure many of us are - in an ES, the driver presses the brake pedal hard, but at the same time, he pushes forward on the steering wheel and forces his body into the back of the seat. This attempts to stop his body going forward.

If the driver didn't lock his body in position and just relaxed - other than pressing the pedal - he would go forward and hit the window. The mere act of braking hard makes the driver support himself. Passengers, OTOH wouldn't be reacting and would be thrown forward.

Same thing on a bike.
The rider pushes forward on the 'bars and forces himself rearwards moving his COG to the rear. If he didn't do that, he would do an immediate header.

Mick F wrote:The COG can be shifted rearwards in an ES situation to keep the weight at the back. I do this naturally and automatically.

you rightly say that you can do it and do do it naturally and automatically. i agree

what i'm trying to say is this; because it's so natural and automatic you can't override your instinct or urge to do it. so you cannot re-create the required conditions to prove or disprove sheldon's theory - so it's pointless to try

i will carry on riding gently and using my rear brake (it's more often than not a coaster and as such is easier & cleaner to use than the front), with the additional use of the front in an emergency situation

Sheldon agrees, of course, about shift weight back.

Sheldon Brown wrote:It is important to use your arms to brace yourself securely during hard braking, to prevent this. Indeed, good technique involves moving back on your saddle as far as you can comfortably go, to keep the center of gravity as far back as possible. This applies whether you are using the front, rear or both brakes.

The following may explain why he is against using both brakes.

Sheldon Brown wrote:Using both brakes together can cause "fishtailing." If the rear wheel skids while braking force is also being applied to the front, the rear of the bike will tend to swing past the front, since the front is applying a greater decelerating force than the rear. Once the rear tire starts to skid, it can move sideways as easily as forward.

As I mentioned above, I reckon I would want to fishtail in a genuine emergency stop.

Sheldon cites John Forester and John Allen in his support, but both these suggest using both brakes.

hubgearfreak wrote:what i'm trying to say is this; because it's so natural and automatic you can't override your instinct or urge to do it. so you cannot re-create the required conditions to prove or disprove sheldon's theory

I gather I am not here or you do not believe me.

Edwards wrote:I gather I am not here or you do not believe me.

the latter. it's be like falling over when walking, not putting your hands forward and landing on your face deliberately.

whilst you can mess about on bikes, you can't override your reflexes

snibgo wrote:Sheldon agrees, of course, about shift weight back.

Yes, he does, but further down in the article and not about ES but general braking. And I like you would prefer fishtailing.

I suppose that the OP question has been hyjacked by me into ES situations. OP was asking if anyone ever used their back brake. Sorry.

hubgearfreak wrote:whilst you can mess about on bikes, you can't override your reflexes

Then I suggest you do a lot of reading up on psychology and how the mind works. You are so very wrong.

The weight shift can be observed on mountain stages of the Tour DE France and a lot of other races. You see the rider going towards the corner and at the last moment they try to put o foot down. If you watch carefully the braking is less effective.
I saw this and did not want to be the one going over the barrier so practiced in places where I had more time and options. This has now become instinct.

So before you think I am a liar. Try this. Ride down a hill with the weight over the rear wheel, then move your weight forward. You will find both brakes do not work so well.
If you do this in a controlled manner you can also release the front brake if you get scared

Edwards wrote:Ride down a hill with the weight over the rear wheel, then move your weight forward. You will find both brakes do not work so well.

i don't doubt it.

as i said we can and do mess around on bikes, see what works & etc.

but in an emergency stop, instinct/reflex would be to shift weight backwards. i couldn't not do it, much like falling forwards whilst keeping my hands behind my back.

i'm not calling you a liar - more like we're not understanding what each others saying

This reminds me of when BMW released their first motorbike with ABS.
The motorcycling journalists were given a brand new BMW on a gravel path and told to ride along and slam on the front brake.
Not one of them could do it first time! Just as Hubgear says years of hard learnt experience prevented them from doing it.
However they watched the BMW test rider demonstrate (just as Edwards did with the TV) and went out and overcame their fears.
By the end of the day they were all able to use that front brake on the gravel.
Just like Edwards says.

Hubbers I said "before you call me". It is the instinct part that we are not in agreement.

I have had 2 years talking to psychologists and others. We are working on how to overcome my natural instincts. This can be learnt depending on how deep seated it is and how you respond to it. My instincts vary from one extreme to the other, so at times I am not bothered by what others perceive as a extreme danger. The other times is being unable to do anything.

If you really want to improve your braking in all situations practice pushing forward with you feet on the pedals, this needs to be done so hard that you are now pulling hard on the bars. It also needs to be repeated so often that it does become instinct.

Thanks Meic that is a very good example

it's me not understanding

are you saying that shifting your COG forward reduces stopping distance?

hubgearfreak wrote:it's me not understanding

are you saying that shifting your COG forward reduces stopping distance?

No.

Shifting your weight/COG forward increases your stopping distance.
This is because you lighten the weight on the back wheel, henceforth you are more likely to go over the bars under hard front braking.
Therefore you cannot brake so hard.

Luck .............

Tigerbiten wrote:Shifting your weight/COG forward increases your stopping distance.

thankyou, that's what i knew - but is edwards saying the opposite, am i misunderstanding, what's going on?

Edwards wrote:If you really want to improve your braking in all situations practice pushing forward with you feet on the pedals, this needs to be done so hard that you are now pulling hard on the bars.e