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Discussion Starter · #1 · (Edited)
Brake modulation (calipers, disc)

First and foremost, I am NOT trying to start another useless disc vs regular calipers brake thread.

That said, I can't wrap my head around why modulation would be better with disc brakes like people always seem to say it is. With smaller distance between pad and braking surface, I would think disc brakes would actually be more touchy. Does it have something to do with hydraulics, and if so does that mean mechanical disc modulation is not good?

I have not had many chances to ride disc brakes, either road or mountain. For road biking I have no plans to change anytime soon from caliper with alloy braking surface, works great for me. But if I buy a mountain bike in the next couple years, it seems disc is the only option.

Anyway, just trying to understand the modulation issue better...

EDIT: Got my terminology wrong and previously referred to canti brakes by mistake (probably from my old MTB days), fixed post as much as possible.
 

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Find a way to ride quality hydraulic disc brakes. Then you will understand.
Spend the day on them. Road or mountain.
 

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First and foremost, I am NOT trying to start another useless disc vs canti brake thread. .
Dude.........You are like ASFOS lite and I love it. :thumbsup:
 

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That said, I can't wrap my head around why modulation would be better with disc brakes like people always seem to say it is. With smaller distance between pad and braking surface, I would think disc brakes would actually be more touchy. Does it have something to do with hydraulics, and if so does that mean mechanical disc modulation is not good?

I have not had many chances to ride disc brakes, either road or mountain. For road biking I have no plans to change anytime soon from cantis with alloy braking surface, works great for me. But if I buy a mountain bike in the next couple years, it seems disc is the only option.

Anyway, just trying to understand the modulation issue better...


Find a way to ride quality hydraulic disc brakes. Then you will understand.
Spend the day on them. Road or mountain.
It's hard to explain, but you'll get it right away if you get on a brake that is very "on/off" (lacks modulation)

I will try.....

Think of well modulated braking in a linear movement. (not a bowel movement, although some brakes are crap)

So, you pull a little you get a little braking

You pull a medium amount and you get a medium amount of brake.

You pull a lot and you get "oh sh!t, I have to stop" kind of braking.

AND................the effort across the entire pull is about the same. You exert x amount of for through most of the lever stroke.
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for brakes with crappy modulation,
You will pull a little and get very little braking
you pull medium and get a lot of braking
You pull a lot and you are locked up before you realize it.


Good modulation does not have a direct correlation to brake power.
 

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Discussion Starter · #5 ·
Thanks, I get the concept of what good modulation is vs bad (no) modulation, I just don't understand how disc brake design leads to better modulation.

Will try to test ride some bikes for kicks.
 

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Just for clarification, am I correct you meant to say "caliper" rather than "canti"? Very few road bikes ever had cantilever brakes.
 

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I think it's because it's hydraulic. There is no change in force required to go from just a little bit on to fully on. You can pull the lever with 1 finger and get the same force as using your whole hand. It's also very linear as other people have noted.
 

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Discussion Starter · #8 ·
Just for clarification, am I correct you meant to say "caliper" rather than "canti"? Very few road bikes ever had cantilever brakes.
Fixed post #1, thanks for catching my terminology mistake. I started on MTB in the mid-90's so that's where thinking of cantis came from.
 

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cut/paste from the interwebs: The greater degree of control comes as the result of a bit of counterintuitive physics. A disc rotor's smaller diameter compared with a rim's brake track means it has to work harder to stop a bike. But because it's working harder, you get better control (modulation), explains Wayne Lumpkin, founder of Avid Brakes and creator of the Ball Bearing mechanical and Juicy hydraulic disc brakes. How much harder does it have to work? According to Lumpkin, disc-brake pads must squeeze with about 1,000 pounds of force to achieve near-lockup, while a rim brake needs only 200 pounds for the same job. The larger span (0 to 1,000 pounds versus 0 to 200) is a bigger window in which to control braking force; hence, better modulation.
 

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Discussion Starter · #10 ·
Thanks, that's helpful. So it's sort of like a torque equation? I didn't think about that at all.
 

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According to Lumpkin, disc-brake pads must squeeze with about 1,000 pounds of force to achieve near-lockup, while a rim brake needs only 200 pounds for the same job. The larger span (0 to 1,000 pounds versus 0 to 200) is a bigger window in which to control braking force; hence, better modulation.
I don't know if I buy that. It terms of percent. 0% to 100% is the range. The range is the same for both. Each system has 0%, 25%, 50%, 75%, etc etc.
 

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I don't know if I buy that. It terms of percent. 0% to 100% is the range. The range is the same for both. Each system has 0%, 25%, 50%, 75%, etc etc.
In terms of percentage has nothing to do with it because your hands aren't programmed to control exact percentage. There's more 'room for play' between 0 and 100 in terms of what your hands can regulate.

edit: I could described what I wanted to much better than that but I'm to tired at the moment to find better words.
 

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Fixed post #1, thanks for catching my terminology mistake. I started on MTB in the mid-90's so that's where thinking of cantis came from.
With cable operated rim caliper brakes you can adjust the geometry of the design to have more or less leverage, and you can adjust that w/ the lever as well. You can also design in the cable pull you want so that in conjunction w/ your brake you get the desired 'power' and 'feel'.

With a hydraulic brake you have piston size (the caliper end of the equation) and master cylinder bore and stroke. The bore/stroke in conjunction w/ the geometry of the lever gives the required feel/power. Just like a cable brake. I went through a few lever/master cylinder designs on my old race moto to get the desired feel and power that I was looking for. I also tried a couple rotors and pad formulas. There are not as many choices in bicycle brakes but you should get the idea. You can do the exact same thing pumping brake fluid as you can pulling cable.
 

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I think the feel is better because there's little to no friction in a good hydraulic system.

Compare good rim brakes with fresh cables to crusty old calipers in need of a rebuild and old worn cables. Much less feel with the old worn stuff.
 

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I think the feel is better because there's little to no friction in a good hydraulic system.

Compare good rim brakes with fresh cables to crusty old calipers in need of a rebuild and old worn cables. Much less feel with the old worn stuff.
To a certain degree, yes. But...you can put together hydraulic brakes that have absolutely no modulation and tons of power, or no modulation and no power...whatever combination you want if you put the right (or wrong) parts together. I've done it...to the detriment of my bank account. More than once. :D
 

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I think it's because it's hydraulic. There is no change in force required to go from just a little bit on to fully on. You can pull the lever with 1 finger and get the same force as using your whole hand. It's also very linear as other people have noted.
Exactly, well said. However, it's not easy to "get it" without trying it first and it takes some time to get used to it.
 

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Thanks, I get the concept of what good modulation is vs bad (no) modulation, I just don't understand how disc brake design leads to better modulation.

Will try to test ride some bikes for kicks.

I think it's because it's hydraulic. There is no change in force required to go from just a little bit on to fully on. You can pull the lever with 1 finger and get the same force as using your whole hand. It's also very linear as other people have noted.
What Devio said above. It's hydraulics. You can do all sorts of things with leverage ratios, fluid volume, hose types, piston numbers, etc.

SRAM has had a horrible track record on hydros in the mtb world. Google "turkey gobble" and you'll see.

Shimano has done way better in the brake department. I'd trust theirs way before SRAMs. I'd given up double tap to get Shimano hydro.
 

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The perfect analogy for the difference in feel to me is non power drum brakes vs power disc on a car - world of difference there and it's the same as the difference between any mechanical brake and hydraulic brake on a bike. I don't many on this forum have ever or will ever have driven a car with manual drum brakes to get an idea of the difference though.
 
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