Braking hard with rear brake.

[slowmotion]

I know you are not supposed to brake hard using just the rear brake. When I was a kid I went over the bars as a result of ramming on the front brake and the memory stuck with me. Ever since I have been wary of the front brake and hardly ever touch it. I know this is appalling behaviour but please spare me the chastisement.

Anyway, here's my question....when braking hard with the back brake, why does the back wheel start coming up alongside the rider rather than staying in a straight line ?

Thank you.

 

[ColinJ]

It does seem like you should be dragging the back wheel behind you, but I think that you start to lose your balance and the back of the bike then just slides towards the front.

You wouldn't have enjoyed what happened on my ride the other evening ... A driver overtook me on the approach to a 20% descent with a hairpin bend and then descended slower than me. I was a bit peeved and tried to make a point by catching up with him. Unfortunately he then decided to brake hard which forced me to. It is a bit scary descending a steep descent towards a nearly stationary car with one's rear wheel coming off the road ...

That's what sensitive brake 'modulation' is about. I was able to carry on braking but not flip the bike. Having said that, it is a feat that I do not intend to repeat in the near future!

 

[Profpointy]

Assuming you're not just teasing us... here's an attempt explanation:

The maximum friction from rubber on road (or anything on anything for that matter) when gripping is more than when it slides. And once it slides, you have less sideways friction as well as braking friction. So, you lock up the back wheel, amount of friction is reduced, so wheel goes straight on (in the direction its going) without any ability to steer (in the direction its pointing). As you're rarely going dead straight on a bike, then tendency is for the back wheel to come round one way or another - especially so if you're using the front brake even a little bit.

 

[slowmotion]

Assuming you're not just teasing us... here's an attempt explanation:

The maximum friction from rubber on road (or anything on anything for that matter) when gripping is more than when it slides. And once it slides, you have less sideways friction as well as braking friction. So, you lock up the back wheel, amount of friction is reduced, so wheel goes straight on (in the direction its going) without any ability to steer (in the direction its pointing). As you're rarely going dead straight on a bike, then tendency is for the back wheel to come round one way or another - especially so if you're using the front brake even a little bit.

No, I'm not teasing. I've heard of "rolling friction". Do gyroscopic forces come into it? A locked up wheel presumably has little tendency to keep rolling in a straight line, whereas a rolling one does. I've noticed the back wheel "coming alongside" when I haven't touched the front brake.

 

[Profpointy]

No, I'm not teasing. I've heard of "rolling friction". Do gyroscopic forces come into it? A locked up wheel presumably has little tendency to keep rolling in a straight line, whereas a rolling one does. I've noticed the back wheel "coming alongside" when I haven't touched the front brake.

doubt if gyroscopic forces have much to do with it. I think it's because once the back wheel locks, there's no directionality so it will go in the direction it is travelling - which may differ from the direction its point so to speak - thus coming round one side or other.

Before it locks it can give some braking force and also some different amount of sideways force so track along the way you want it to go.

(sorry, that's not clearly put, but maybe best I can manage)

 

[slowmotion]

Actually, come to think of it, one usually only brakes really hard when trying to avoid a sudden obstacle so maybe steering and locking up the back wheel comes into it. If I'm feeling brave, I'll try and lock up the back wheel while going straight down a length of clear tarmac and see what happens. Thanks for the input. Keep it coming

 

[theclaud]

I have been wary of the front brake and hardly ever touch it. I know this is appalling behaviour but please spare me the chastisement.

Not a hope.

 

[slowmotion]

Not a hope.

Oh! Cruel Mistress....

 

[Citius]

Anyway, here's my question....when braking hard with the back brake, why does the back wheel start coming up alongside the rider rather than staying in a straight line ?

Thank you.

It can go left (if your bodyweight lets it), it can go right (if your bodyweight lts it), or it can go over the top (if you balance properly and don't moderate the braking force).

 

[slowmotion]

It can go left (if your bodyweight lets it), it can go right (if your bodyweight lts it), or it can go over the top (if you balance properly and don't moderate the braking force).

One would have thought that, if the bike's going in a dead straight line and the rider isn't leaning, that the locked up back wheel would tend to act like a trailed sea anchor does for a boat....that is, keep the bike in a straight line. BTW, I don't use the front brake at all.

 

[theclaud]

I reckon Slowmo is in the wrong cycling discipline. He gets bonus points if he can tell us who these people are, without Googling:

Robert Cardoza, Bob Haro, Greg "Ceppie" Maes, David Lee and Grant Meyers.

 

[slowmotion]

I reckon Slowmo is in the wrong cycling discipline. He gets bonus points if he can tell us who these people are, without Googling:

Robert Cardoza, Bob Haro, Greg "Ceppie" Maes, David Lee and Grant Meyers.

They sound like a bunch of rather overexcitable celebrity chefs to me. I imagine a meal at Greg "Ceppie" Maes' establishment could be horrendously, ruinously expensive.
Do I win?

 

[MichaelW2]

bikes steer by balance and balance by steering. You just lost a lot of steering control by braking, so the bike unbalances sideways.
Seriously, learn to trust your front brake. You only go "over the bars" if you do it wrong:
Very upright position.
No bracing of arms.
Sudden grab at brakes.
The bikes stops but you don't.

To brake safely, set your centre of gravity low and rearward. Brace your arms. Brake progressively, applying just as much braking force as the tyre can apply.

 

[slowmotion]

bikes steer by balance and balance by steering. You just lost a lot of steering control by braking, so the bike unbalances sideways.
Seriously, learn to trust your front brake. You only go "over the bars" if you do it wrong:
Very upright position.
No bracing of arms.
Sudden grab at brakes.
The bikes stops but you don't.

To brake safely, set your centre of gravity low and rearward. Brace your arms. Brake progressively, applying just as much braking force as the tyre can apply.

Thanks Michael. I'll try and practice that and I'm grateful for the advice. It's much appreciated.....but I'm still curious as to why my back wheel seems to want to snog my armpit.

 

[threebikesmcginty]

I reckon Slowmo is in the wrong cycling discipline. He gets bonus points if he can tell us who these people are, without Googling:

Robert Cardoza, Bob Haro, Greg "Ceppie" Maes, David Lee and Grant Meyers.

They were all stoned to death for 'rear brake only' stopping.