• Hang on, what's the point of 4 pots anyway? They dissipate more heat or deal with water better or what? They move smoother?

    You're just applying the same force over double the area so power's the same shirley (for a given lever)

    I have 4 pots and I don't know why

  • Hang on, what's the point of 4 pots anyway? You're just applying the same force over double the area

    In the idealised implementation, you're apply the force over the same area (same size master cylinder, twice as many caliper pistons each with half the area). The advantage is that the pad area is concentrated towards the outer rim of the rotor, so although all the forces are the same, the torque is slightly amplified as the mean radius of action is increased.

    If you have power-assist, you can apply the same force over an extended area, and if you can't increase the rotor diameter due to packaging issues, that's a good way to get a big increase in brake power. Neither applies to bicycles.

    The current Shimano 4-pots use differential pistons, with the leading piston being smaller. This means there's less force on the leading half of the pad, which is said to benefit modulation and eliminate chatter (noise)

    A minor benefit is that the radial depth of the rotor track is reduced, so the rotors can be slightly lighter. This is particularly evident with composite rotors, since you're cutting steel and adding aluminium, but even applies to monolithic steel rotors.

    The main benefit on a bicycle is that 4-pots just look cooler

  • 4-pots just look cooler


  • Yup, 4 > 2.

    Many MTB 4 pot (shimano, magura, formula, sram) have more pad area too, so little bit more meat = lasts more than a day in the mountains.

    Harder to get 'just so' as a longer profile pad = has to be set spot on so you don't get pad rub at the edges of it. Magura E4 (right name?) that come on loads of bikes now a bit of a pain to get centred.


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