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Disk Brakes: Pad Design

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Disk Brakes: Pad Design

Old 05-18-22, 08:18 AM
  #1  
sjanzeir
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Disk Brakes: Pad Design

So, I haven't actually researched any of this before because, outside of a thoroughly academic context, I wouldn't know where to start.

Correct me if I'm wrong, though...



All things being equal (which in reality they just cannot be, given that these two pads will fit completely different calipers that are actuated by different brake levers...)

The longer, narrower pad will have a more gradual braking effect, but will feel smoother in action and easier to modulate, whereas the shorter, wider pad will furnish a harder initial bite but with less finesse in action. Am I in the ballpark?
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Old 05-18-22, 08:26 AM
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Seems like you think the pads of all models of brake should work with any model.

Or am I missing what your question is?

If you look at where the pads sit on the rotor, it may well be in the same place between the two different models. The length to the attach point means nothing for where they will contact the pad. Unless you put them in the wrong brake body.

Last edited by Iride01; 05-18-22 at 08:35 AM.
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Old 05-18-22, 08:38 AM
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Seems like you skipped over the entire post - especially the second paragraph:

Originally Posted by sjanzeir View Post
All things being equal (which in reality they just cannot be, given that these two pads will fit completely different calipers that are actuated by different brake levers...)
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Old 05-18-22, 08:47 AM
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With different brakes using different pads: Pad material is different, so friction will be different. Hydraulic leverage is different, so yeah, they will be different. I'm guessing the bigger pad will be more powerful in all aspects, unless the caliper design is not as effective. Are you looking for more initial bite, or is that not a good thing? So many variables... you cannot "Mix and Match" the above pads. What was the question? NO! You are not in the ballpark.
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Old 05-18-22, 08:50 AM
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Originally Posted by sjanzeir View Post
Seems like you skipped over the entire post - especially the second paragraph:
Yeah, but you didn't wait for my revision to clarify exactly what I was referring too. I do see how you saw it that way.

You have to realize that different models of disc brake also have different sizes and different numbers of pistons pushing on the brake pads.

Last edited by Iride01; 05-18-22 at 08:53 AM.
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Old 05-18-22, 09:12 AM
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I guess that I'm not sure of why the question is being asked - the brake pads are going to work within the parameters of the system and the intended use. Are you planning on doing some modding so that you can squeeze calipers on to a bike for which they weren't intended?


Having used a few different Shimano hydraulic road calipers with several different types of pads, there's no shortage of modulation control or braking power within the context of road riding. I would be surprised if the braking systems for other types of riding weren't similarly suitable.
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Old 05-18-22, 09:13 AM
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Not really, the master/slave and thus the amount of fluid pumped and how fast it is pumped make the difference. Those pads are different shapes only to fit the calipers they work with. The larger pads fit a 4 piston caliper, the smaller a 2 piston. The brakes will perform differently because the whole system is designed to perform differently, not just because they have different pad shapes.
Why do people over-think so often?
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Old 05-18-22, 12:19 PM
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^^What he said. It's also important to note that surface area of the brake pad does not directly influence braking power like you might think.
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Old 05-18-22, 01:34 PM
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Originally Posted by freetors View Post
^^What he said. It's also important to note that surface area of the brake pad does not directly influence braking power like you might think.
Surface area might affect braking power....But OP is speculating that the shape of the surface might have an impact. (I think that is probably not true, and it's irrelevant anyway. Buy good brakes and pads of one -- and only one -- shape will fit them.)
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Old 05-18-22, 01:54 PM
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You might get a few seconds longer before they glaze with the longer/wider rectangular ones. How they all bite are correlated to the materials used, driving the friction coefficient.
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Old 05-18-22, 05:59 PM
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It's not a stupid question to ask if it's quantifiable why one brake feels different from another. But this isn't the main reason, just as everyone is saying.

The force you apply at your finger and the force you get at the tire are mostly about leverage and that's true of any kind of brake. If you want an "all else being equal" experiment the easiest things to change are the pad compound (there are more than two) and the rotor size (changing the leverage ratio from tire to rotor)

But back on the topic... If all things are permitted to be not equal. If you think about the pad and the pistons together, the 4-piston brake has smaller pistons leading so that the pad force is "toed out" just like you'd toe out the pads on a rim brake, and that does lead to a change in feel. 2-piston brakes can do the same thing with offsetting where the piston pushes on the pad, but only a little, so it doesn't cock the piston.
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Old 05-19-22, 03:15 PM
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So, we're trying to correlate brake performance by analyzing pad shape?

I would think design factors like caliper type / # of pistons, MC style (radial / axial) and rotor size would make a much more quantifiable difference; pad shape is just the result of the size /shape interface between the caliper and the rotor. Bigger, multi-piston calipers would have bigger, longer pads than smaller, single piston calipers.
(Kinda what i've noticed from all the brake jobs i've done over the years)
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Old 05-19-22, 05:58 PM
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Originally Posted by sjanzeir View Post

The longer, narrower pad will have a more gradual braking effect, but will feel smoother in action and easier to modulate, whereas the shorter, wider pad will furnish a harder initial bite but with less finesse in action. Am I in the ballpark?
What's your reasoning behind this statement?

Personally I would think (for a given surface area) the pad shape i.e. length v width is largely irrelevant to any of the qualities you mention above.

From my own limited experience of hydraulic brake design, one of the most important (and often over-looked) factors regarding "feel" is how rigid the caliper body is (stiffer the better). Obviously pad material is very important too, along with the hydraulic circuit itself.

Last edited by PeteHski; 05-19-22 at 06:05 PM.
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