Braking

[pete75]

Yes, I believe you're right, but SB wants no rear braking.

My point is that BOTH is better than front only.

But he doesn't Mick.
He goes on to say :-

When to Use The Rear Brake
Skilled cyclists use the front brake alone probably 95% of the time, but there are instances when the rear brake is preferred:
Slippery surfaces. On good, dry pavement, it is generally impossible to skid the front wheel by braking. On slippery surfaces, however it is possible to do so. It is nearly impossible to recover from a front wheel skid, so if there is a high risk of skidding, you're better off controlling your speed with the rear brake.

Bumpy surfaces. On rough surfaces, your wheels may actually bounce up into the air. If there is a chance of this, don't use the front brake. If you apply the front brake while the wheel is airborne, it will stop, and coming down on a stopped front wheel is a Very Bad Thing.

Front flat. If you have tire blowout or a sudden flat on the front wheel, you should use the rear brake alone to bring yourself to a safe stop. Braking a wheel that has a deflated tire can cause the tire to come off the rim, and is likely to cause a crash.

Broken cable...or other failure of the front brake.
Long mountain descents, when your front brake hand may get tired, or you may be at risk of overheating a rim and blowing a tire. For this situation, it is best to alternate between the front and rear brake, but not to use them both at once.

When to Use Both Brakes Together
Generally I advise against using both brakes at the same time. There are exceptions, however:

If the front brake is not sufficiently powerful to lift the rear wheel, the rear brake can help, but the best thing to do is to repair the front brake.
Typical rim brakes lose a great deal of their effectiveness in rainy conditions, so using them both together can reduce stopping distances.


Long or Low bicycles, such as tandems and long-wheelbase recumbents have their front braking limited by the possiblity of skidding the front wheel, since their geometry prevents lifting the rear wheel. Such bikes can stop shortest when both brakes are applied.
Tandem caution: when riding a tandem solo (no stoker on board) the rear brake becomes virtually useless due to lack of traction. The risk of fishtailing is particularly high if a solo tandem rider uses both brakes at once. This also applies to a lesser extent if the stoker is a small child.

[Mick F]

If your DP brakes cannot throw you over the bars, they are not properly set-up!

Oh, but they are.

In practice, is what I'm talking about. In theory, I'm sure I could, if I wanted, lean forwards and brake hard on the front, and go over. But I would have to actively encourage the situation. Even sitting normally, I wouldn't go over. I might fall off to the side with a front wheel skid, though!

Maybe this has something to do with grip too? My skinny 20mm 100psi tyres possibly can't lock up AND grip enough to throw me over? I would provoke a front-wheel skid long before upsetting my centre of gravity forwards.

Practice is what I'm talking about, not theory.

[Mick F]

Yes, I believe you're right, but SB wants no rear braking.

My point is that BOTH is better than front only.

But he doesn't Mick.
He goes on to say :-

When to Use The Rear Brake ....................

Our posts crossed in the post!

SB says that an emergency stop will only need the front brake, except for the situations you quote. Without those conditions, all you need is the front.

I maintain that both brakes are needed all the time, but to use them wisely.

It works for me.
Try it yourself.

[Velo]

If your DP brakes cannot throw you over the bars, they are not properly set-up!

Oh, but they are.

In practice, is what I'm talking about. In theory, I'm sure I could, if I wanted, lean forwards and brake hard on the front, and go over. But I would have to actively encourage the situation. Even sitting normally, I wouldn't go over. I might fall off to the side with a front wheel skid, though!

Clearly YMMV, as this is not my experience at all. I have carried out controlled over the bars dismounts, stoppies/endos due to emergency braking and I have also applied excessive braking force and gone over the bars when trying to wipe off too much speed in order to avoid a collision (with weight downwards and rearwards, arms braced etc).

[byegad]

My Trice QNT has two front brakes and no rear one. The reason being that under hard braking it is possible to lift the rear wheel and so 'peck' the road with the large chainring out infront. It is possible to fit a rear brake but it is for parking only as it will lock very easily.
My Azub recumbent with V-brakes will squeal the front tyre and the rear gets so light that it will lock up on even a very light pressure on the back brake lever.
If a conventional bike's front brake cannot lift the back wheel on a good, dry, level road with the rider moving his/her body back as far as possible to avoid the rear wheel lifting, then that wouldn't be my idea of a good brake.
Maybe I'm spoilt but, the Azub, as a product of it's configuration, has the centre of gravity lower and further back than any road bike ride could achieve. All my uprights use V-brakes and will lift the back wheel on dry roads and the Trice with drums will comfortably out brake any standard bike without pecking.

I would agree with MickF in that in the real world with roads as they are the risk of a front wheel lock up on two wheels is such that it is preferable to use both brakes all the time. But Sheldon is right in that under maximum braking the rear wheel SHOULD be so unweighted as to be useless in stopping the bike, as indeed it usually is on its own if you want a short stop!

[Auchmill]

Surely whether the cyclist goes over the bars depends on the forces involved. If the braking force is sufficient and the momentum adequate then over the bars you will go. Tandems may be difficult to rotate but presumably not impossible given enough force. You may have to travel at 200mph to achieve it.

[byegad]

Surely whether the cyclist goes over the bars depends on the forces involved. If the braking force is sufficient and the momentum adequate then over the bars you will go. Tandems may be difficult to rotate but presumably not impossible given enough force. You may have to travel at 200mph to achieve it.

That'll be down hill then?

[Mick F]

Just reading about SBs death.

Sad.

[meic]

Andy insists that "for skilled users in good conditions the front brake is sufficient" and he relies on physics.
I think we all agree on that except we may wish to replace the word "skilled" with "perfect" and then point out that such people are rare.
Now when doing a front only braking stop at the critical point of rear wheel losing contact, does it actually do any harm to be applying the back brake?

As we dont normally ride in good conditions we have to carry the back brake around anyway so we might as well use it. Then when we fail to reach the perfect front wheel braking point our back brake is helping.

On Mick's braking test he may well hit lucky and acheive equally good braking with front brake alone as with both brakes, it wont happen often!
If he does better with front brake only than with both brakes then either our knowledge of physics is in adequate or some other factor made the tests unequal.

After a good long discussion I think we are coming to an agreement, do you?

[Ben Lovejoy]

I used to be involved in IAM motorcycle training, and we carried out some tests comparing rear, front and both brakes.

At the limit, the rear brake had no effect at all for precisely the reason SB suggests: it is totally unweighted, and the rear tyre thus has no friction.

However, most people are afraid of going over the bars or the front wheel tucking under, so don't use maximum braking on the front. Thus in the real world, as Mick found in his tests, the rear brake will contribute.

Ben

[Mick F]

Thanks guys.

We live in a Real World and we ride Real Bikes in a Real Environment.

What I object to about SBs account, is that his explanation is black and white. The Real World is all shades of gray.

[AndyB]

Now when doing a front only braking stop at the critical point of rear wheel losing contact, does it actually do any harm to be applying the back brake?

Well, according to both Sheldon, and my experience, using the back brake when braking really hard can cause fishtailing. Okay, it's easily controlled by releasing the rear brake, but not a great sensation when you're trying hard to stop.

What I object to about SBs account, is that his explanation is black and white.

That's harsh - his page has a long list of situations when it's a good idea not to just use the front brake.

However, most people are afraid of going over the bars or the front wheel tucking under, so don't use maximum braking on the front. Thus in the real world, as Mick found in his tests, the rear brake will contribute.

True, I'm sure. It was interesting to read one of the links from Sheldon's page - the guy there was suggesting that most people didn't need to brake so hard that the rear wheel started to skid with 25% braking applied to that wheel. In other words brake with a ratio of power of 3:1 front:back.

After a good long discussion I think we are coming to an agreement, do you?

I think so... the main thing is understanding what can happen, what might happen, and what can be done about it.

[fatboy]

My two pennies worth! This is about the only thing on his great website that I thought "now hold on a moment". I sort of see the point but I still don't quite believe that only using one brake is better than two. I guess the issue is that under hard braking when the back of the bike is so unweighted that it has no weight the back brake can only cause the back wheel to skid and hence loose control.

However for all that I always instinctively grab both brakes at once, probably because I've never had a bike with truely great brakes. I'm thinking about getting some "froglegs". Maybe they'll stop me better!

[Mick F]

That's harsh - his page has a long list of situations when it's a good idea not to just use the front brake.

Yes. Agree. But not harsh. He puts that section as an add-on.

But if he'd said at the beginning of the article that using both brakes was normal and advisable in just about every situation in just about every road surface, especially at speed, I'd have been happy.

I would also have been happy had he said that in theory, in a perfect world on a perfect surface with perfect brakes, all you need is a front one!

I can't and won't argue with science. The front brake only situation is right. But only in theory. The Perfect World only exists in theory.

[pigman]

Interesting debate. FWIW, I'm not really into the lab conditions physics. As someone says its real world stuff that counts. Couple of observations from me.
1. Years ago, I was descending through chatsworth park on an evening (lined-out) chaingang. Suddenly, some cows came onto the road and everyone did emergency stops. I applied the front brake too hard and managed to lift the back wheel up quite significantly bofore I fortunately let go and dropped down. (no-one actually crashed and we resumed said line-out).

2. bikes throughout the ages have been equipped with a front and a back brake. Some might argue that it still exists as so, because no one has challenged convention, but I'm sure that if front brake only was the way to go, the pro teams that have budgets running into millions would have done this. If the rear brake was there as a back-up only, it would make sense to have the two calipers, one in front of and one behind the fork crown and hence have front braking only along with a secondary back-up caliper.

I'd personally like to keep things as they are and have all wheel braking, rather than have it all focussed onto one wheel. But, i'm no scientist ...