weak rear brake -- a feature, not a flaw

[AlanDog]

My 1981 cx500 has a great feature, it has a rear drum that is impossible to lock up. Maybe if you jump on the pedal, but pushing down hard will not lock it up (but it definitely does help the bike slow down quicker). Shouldn't all bikes be like this? Having practiced and having had to actual do panic stops to avoid hitting cars on the 250, I have totally bought into Alex's idea that it seems to basically take 100% of your attention when stopping quickly to just modulate the front brake for maximum braking power. Locking up the rear does help you stop, but one thought I have is I could 'upgrade' the 250 to a weaker rear brake. Any thoughts or ideas on how this would be done? Make the pad surface area smaller? Drum brake upgrade?

Yes, I know I can practice, practice, practice. But my experience is that panic braking occurs when you are in a panic. And my practice sessions seem to show that it takes incredible focus to modulate the rear for maximum braking.

[Domagoj]

Originally Posted by AlanDog

Yes, I know I can practice, practice, practice. But my experience is that panic braking occurs when you are in a panic.

This is very true.

You can try some terrible brake pads. It requires no modifications and the brake will be significantly less powerfull.

[cuong-nutz]

I would still go with practicing panic braking. Could also throw in engine braking by down shifting. Switching to organic rear brake pads may help or adjusting the rear brake to need more pedal to apply same braking force.

[alex.s]

if you are set on the bike well and aren't jumping whoops, you can accurately move the pedals. but its a bitch to move them hard. so the less input you have to give, the more precise you can be with it.

why you would use a rear brake is another story

[NathanUc]

Sort of related, but I use GG grade pads on the rear instead of HH to help reduce lock up. While it would still lock up if I tried, it's extremely unlikely myself or anyone else on my bike would lock it without deliberately trying.

[Alex]

Old-tech ABS, just make the brakes too weak to be able to lock the wheels at speed.

[Linuss]

Originally Posted by AlanDog

Locking up the rear does help you stop

Only because you're using both brakes instead of just one.


Locking up the brake provides less stopping power than correctly modulating it and letting it still spin.

[Motofool]

The lock up of the rear tire during really strong braking of the bike will happen, regardless the rear brake power.

At 1g deceleration, all the weight moves forward, leaving the rear tire literally in the air, or at least reducing the friction force between asphalt and tire to near zero.

"The obvious mathematics of the situation are that the front wheel can do 100 percent of the braking and the back at that point just locks up no matter who you are. Learn to totally rely on the front brake for quick, clean stopping; then, if you still have a use for the rear, go ahead and use it. But realize that the rear brake is the source of a huge number of crashes both on and off the track." - Keith Code

[AlanDog]

Originally Posted by alex.s

if you are set on the bike well and aren't jumping whoops, you can accurately move the pedals. but its a bitch to move them hard. so the less input you have to give, the more precise you can be with it.

why you would use a rear brake is another story

Jumping whoops? Not quite getting what you're saying...

So it sounds like some people say not to use the rear brake at all... how common is this thought? Clearly, it will help you stop, and as long as your going in a straight line, locking up doesn't usually cause a problem. Is this an old debate? Well, I think my upgrade is a real possibility. So the pregen 2007 comes with HH pads stock in the rear? What about cutting grooves into the pad with like a dremel or circular saw to reduce the surface area?

[Motofool]

Some racers even disconnect or remove the rear brake.

The rear brake will help you in normal braking, but not much for emergency stop after the wheel stops turning.
The skidding friction is much lower than the rolling friction.

Check these brake articles:

http://www.msgroup.org/Articles.aspx?Cat=2

[dfox]

as motofool stated above, if you're braking, your momentum pushes you onto the front wheel.

Braking force is directly proportional to the weight exerted by the wheel (f=mu*m*g, m*g being weight). If you're almost doing a stoppie because you're stopping so hard, there's basically no weight on the rear tire, and any ammount of force on the rear brake will lock it up.

IMO, the rear brake is there more to reduce the wear on the front brake and more ballanced breaking during average riding. In a panic, don't bother with the rear brake because you're so likely to lock it up and have it slide out from under you.

cliff notes: weak rear brakes prevent you from accidentally locking when you're not in an emergency, but in an emergency, anything can lock the rear wheel.

[akima]

Alan: I solved your problem by deciding to use only the front brake in emergency stops. I use the rear for other situations (like gently braking on a loose/non-grippy surface. Holding the bike in place on an incline when at a stop. Coming gently to a stop.)

There seem to be plenty of people here who brake front only and plenty who brake with both brakes. I just made this poll to get an idea of the numbers.

[KawiKid860]

Rear brake + 2 up = awesome. I can almost stand on it and it will stop me easy without locking, but even in 2 up emergency stops I've locked the rear for that millisecond. I keep in practice using both brakes for emergency stops, but I've never been in a situation where I have to stop as quick as possible to avoid damage, injury or worse. I also use the rear + engine braking in normal riding to require less effort with the front brake and again just to stay in practice.

[akima]

Originally Posted by KawiKid860

Rear brake + 2 up = awesome. I can almost stand on it and it will stop me easy without locking

Wow! I've never had a passenger before so I don't know what that feels like.

[AlanDog]

Originally Posted by Motofool

Some racers even disconnect or remove the rear brake.

The rear brake will help you in normal braking, but not much for emergency stop after the wheel stops turning.
The skidding friction is much lower than the rolling friction.

Check these brake articles:

http://www.msgroup.org/Articles.aspx?Cat=2

cool link, thanks. I still think that the optimum solution is to simply have a rear brake that will not lock up. Another great thing about the weak rear brake is that it's much easier to modulate during regular riding. I understand the argument that almost all the weight is on the front in an *ideal* emergency stop, but being able to use the rear is like an insurance policy for when your front braking is not ideal. So weaker rear brake modification has only positives, and no negatives.