Edit: To Clarify this is regarding going as fast as possible, i.e. racing, off-road.

I can't see why "modulation" matters so long as you have enough to apply near maximum braking force without locking the wheel.

Surely the brakes should always be used to near maximum stopping power, while using the duration of application to give the desired deceleration in as little time as possible (as late as possible)?

Wouldn't any other approach be inefficient and result in riding slower?

I have held this (logically derived) belief for a while and been around similarly minded people, but recently I have come across a surprising amount of people who always go on about modulation when brakes are being discussed and how they need great modulation to get "just the braking power they want".

Is their preference a matter of what they want trumping what they actually need for maximum efficiency?

I was always led to believe (with sensible reasoning) that dabbing or feathering brakes or in any way applying them, to anything other than near maximum capacity, is simply incorrect brake use (when efficiency is at stake.)

Am I missing something?

  • 1
    I think its a heat thing - clear on-off breaking will leave the rim and therefore the tyre cooler than a long slow gentle rubbing. I've always found that if I want full breaking, my butt has to be hanging out the back of the bike as a counterweight. – Criggie Jan 28 '16 at 6:04
  • Surely the brakes should always be used to near maximum stopping power I hope you don't put that kind of logic into practice on all vehicles with brake systems – stijn Jan 28 '16 at 10:18
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    I put that logic into practice on every vehicle where I am trying to go as fast as possible. – Purr Jan 28 '16 at 14:41
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    This braking strategy would be a nightmare in any group setting. – Paul H Jan 28 '16 at 15:14
  • @Paul H do you realise that on a downhill the only people who could be adversely affected by this kind of braking must be doing it themselves to an even greater extent themselves and be behind me? Furthermore they would only be affected if they are hell bent on doing this somewhere they cannot overtake and decide to do it anyway and run into my rear because they are doing what I am doing but even more extremely and with total disregard for the facts of reality such as bikes ahead of them. Any braking strategy that ignores reality would be a nightmare in any setting! – Purr Jan 28 '16 at 15:56

If by efficiency you mean braking power then yes maximum braking power is right at the verge of locking up.

Braking does not need to be performed at maximum braking power. Often you don't need to slow down or stop as fast as possible.

There is static and kinetic friction. Kinetic is when the wheel skids. Kinetic friction is lower so once you start to skid you have less braking power. Maximum braking is right up the edge before you skid. The trick is know where that is so modulation is used. But if you know right where the edge is then no need to modulate.

Off road where surface varies it is very hard to know exactly where the maximum is so even very good riders get near that edge and modulate.

ABS in cars auto-modulates. Race cars do not have ABS as if you know where the edge is then that is maximum braking. I disabled ABS in my sport car.

For longer braking like a long down hill then modulate to cool the brakes. But that is a different modulation in you should come all the way off to get some air cooling between the brake surface and the pad.

More discussion from OP on modulation.

If you know right where the edge is then no need to modulate

If you know exactly where the edge is then you stay on that edge and that is maximum braking. The problem is you don't always know exactly where the edge is. Modulate near the edge is way to manage that unknown. You are accepting that you will spend some time in the kinetic range. Let's say you know within a 5% error where the edge is then you would be better off just braking at 95% if the ratio of static / kinetic > 1 / .95.

Sorry to get mathematical on you but your mental estimate of max static is more like a bell curve. So if you come off max by 5% and still modulate you may only be in the kinetic range 5% of the time. If you feel yourself in the kinetic range more then you back off. Modulation is both a method to manage and measure the unknown max static.

In real life you push it and then back off. This is OK in a straight where you can skid and typically not fall. Into a corner it is more problematic as a skid can turn into a fall. Max braking is not typically the fastest way around a track.

  • By efficiency I meant getting round the trail as fast as possible, but that requires the hardest and latest braking, thus intertwining it with braking efficiency. Oh and downhill yea it's like, feel like I might loose control, brakes on, don't feel like I am about to die anymore, brakes off, repeat :) (Not a very technical explanation, but just voicing my agreement.) – Purr Jan 28 '16 at 15:10
  • 1+ but, does the ABS like modulation to maintain maximum practical braking actually count as more modulation than necessary to stay at maximum braking power? Or is it covered by "enough to apply near maximum braking force without locking the wheel"? – Purr Jan 28 '16 at 15:18
  • @purr Where do I assert ABS is "maximum practical braking"? Would I make the point ABS was not used in race cars if ABS is optimal braking? ABS is safe braking. – paparazzo Jan 28 '16 at 15:28
  • You did not, and you would not. Having considered those two questions I can now answer my own question with: ABS like modulation is not covered by the modulation necessary to stay near max. braking force. I can also conclude ABS like modulation is a good reason for more modulation than necessary for maximum efficiency. However I can also conclude that the answer to my original question must be simply "No." – Purr Jan 28 '16 at 16:10
  • You are not following the mechanics of modulation nor my answer. "But if you know right where the edge is then no need to modulate." I will try an update. – paparazzo Jan 28 '16 at 16:13

You say "Surely the brakes should always be used to near maximum stopping power". This is where the first need for modulation comes from. Stopping power has at least as much to do with grip between the wheel and the road than the torque your brakes can except on the wheel. Maximum stopping power comes from the front wheel (plenty of discussion about that here) and you really want that to not skid. Thus you need to modulate the front brake if you're riding on varying surfaces. Similarly if for some reason you need to brake on a bend, you'd better make it gentle. In both these cases pulsing the brakes at a humanly-feasible frequency won't help - the initial loss of traction when you jam them on its what will start the skid. I don't think you can assume perfect or even constant grip anywhere let alone on a trail. Think of leaves on a packed surface - the grip can deteriorate with little to no visible change. A bike set up for one set of conditions will be used in a variety. By using your brakes only at max strength (which would have to be quite high) you're removing a useful degree of freedom.

Riding in traffic - as you may do on any bike, even if just to get to a trail. you may want to go slowly to catch a gap or just because you're stuck in a queue. Your pulsing technique would work better here, however it makes for a very jerky ride - not what you want if one hand is off the bars to signal, especially if it's the hand that works your front brake. It wouldn't really be a good idea to set up a MTB that couldn't brake gently. In design you also have to assume a rider who is inexperienced of unfamiliar with the conditions; the latter especially may want to brake progressively which requires modulation.

  • i did say, regarding modulation, "so long as you have enough to apply near maximum braking force without locking the wheel". However I will +1 this because situations where you only have one hand on the bars and need to brake is imo a valid case for more modulation, even if it is a situation I have never found myself in while mountain biking and rarely while road biking. – Purr Jan 28 '16 at 14:50
  • @Purr A right turn (across traffic) at the bottom of a hill seems common in this hilly city, so signalling while only braking at the back. – Chris H Jan 28 '16 at 16:35
  • @Purr You should clarity that you mean max braking is a race type conditions – paparazzo Jan 28 '16 at 16:37

In the hypothetical case where you can get accurately from zero braking to edge of traction, you still need to consider jerk: https://en.wikipedia.org/wiki/Jerk_(physics), especially part "Physiological effects and human perception of physical jerk".

In reality, you still need modulation to adapt to differences in traction. Also, your XT brakes are fine and those who make fun of them don't know what they are talking about.

  • I like that jerk article, didn't realise that was also the technical term! – Purr Jan 28 '16 at 18:15

Inherently, a lack of modulation provides a lack of "feel" to your braking. That lack of feel translates into an On or Off level of braking rather than a gradual application of the brakes. Accurate braking to scrub of speed means faster cornering out on the trails (or road). Carrying the right amount of speed into corners means carrying more speed out of the corner. And I would have thought the amount of force required to brake - below the locking threshold would vary due to rider weight, speed and terrain. So a brake only being able to apply near maximum braking force would be irrelevant.

  • I cannot follow this argument, how is gradual application superior to maximum application? Surely it is inferior? If person X brakes gradually, this means overall he brakes slower, which in turn means he has to start braking earlier, which means overall he takes longer to get to the turn at the correct speed. Surely the braking of person Y who slams the brakes on to the edge of grip, at the last moment, for just long enough to get the speed down to take the corner, would be more "accurate" than some one braking gradually? – Purr Jan 28 '16 at 14:56
  • Regarding your last two sentences, yes this would vary from rider to rider, I feel I cover that with "so long as you have enough to apply near maximum braking force without locking the wheel" I do not specify a static amount of modulation but rather "you have enough" which is variable person to person. – Purr Jan 28 '16 at 15:01
  • @Purr If you don't agree then don't use the input. As last as possible at maximum braking is not as accurate. If you as too late then fail. – paparazzo Jan 28 '16 at 15:10
  • I agree with the obvious idea that failure is not accurate. – Purr Jan 28 '16 at 15:22
  • @Purr - if you want to be fast on a bike - you have to be smooth on a bike. Decent modulated brakes accommodate this. If all corners in life were hair-pin your point would be valid .... – OraNob Jan 29 '16 at 7:27

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