I dont know the scientific/engineering/ reason why bigger rotors equals more stopping power (to me if something makes the wheel stop whether it be a 180 rotor or a rubber block on a road bike rim then it does the job just as well as any braking mechanism)but I know it does, so why doesnt a bigger brake pad have more stopping power? Or maybe it does and if that is the case why havent manufacturers made them?
friction isn't area dependent.
bigger rotors work due to more leverage (pad centre to axle)
The main reason is the pad dissipates heat onto the disc, then air hitting the disc cools it. Also if the diameter of the disc is bigger then there are more rotational forces to use/act on the rotating wheel!
Ignoring heat dissipation and scientific calculus jargon, its a leverage thing. A bigger disc is further away from the hub center therefore when the brake is applied, less force is needed on a larger disc than a smaller one to stop the wheel due to the distance between the two points. Ie, spin a wheel and stop it by touching the tyre, now spin the wheel and try to stop it by touching the hub flange. Simples.
The standard friction equation is
F = u x N
Where F is the force required to move an object, u the coefficent of friction, and N is the force clamping the two objects together.
Area doesn't come into the equation, so doesn't effect the result*
*Though reality is quite a bit more complicated 🙂
Big pads big calipers big weight
original XT fourpots, hope something or others, avid code, new XO's
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TheSwede - MemberIgnoring heat dissipation and scientific calculus jargon, its a leverage thing. A bigger disc is further away from the hub center therefore when the brake is applied, less force is needed on a larger disc than a smaller one to stop the wheel due to the distance between the two points. Ie, spin a wheel and stop it by touching the tyre, now spin the wheel and try to stop it by touching the hub flange. Simples.
Why has nobody developed a brake that shoves a rod into the spokes? Instantly locks up the wheel, even with one finger.
It's the future, I tell you.
They already do. The pads on my Hope M4 Evos are much bigger than the ones on my old Avid Elixirs. The pads on the Hope V2s are bigger still. I presume the new 4 pot Avids also have bigger pads than the 2 pots.