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Brake Hydraulics


Jenny Pryde

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Pascal's Principle...master cylinder ratios...caliper piston sizes. Bleurgh. Can someone de-mystify how to pair master cylinder and caliper(s), please? So they retain braking power AND feel?

Anyone with a background in the physics of hydraulics who can communicate the facts clearly?

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  • 1 month later...

its force over area, the smaller the master cylinder the more force you can produce but you sacrifice feel, if you use a bigger cylinder then you get more feel and less force, what are you trying to do? i take it you have calipers from one thing and your trying to match the master cylinder, best bet is to use a m/c the same size as the standard one for the calipers your using, quick google should have you with the correct size and go from there.

edited for cocking it up!

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its force over area, the bigger the master cylinder the more force you can produce but you sacrifice feel, if you use a smaller cylinder then you get more feel and less force, what are you trying to do? i take it you have calipers from one thing and your trying to match the mastercylinder, best bet is to use a m/c the same size as the standard one for the calipers your using, quick google should have you with the correct size and go from there.

Fundamental error in this discription. When you use a master cylinder with a smaller diameter piston, you get a higher line pressure, hence more force on the pad, for a given lever force, than you would witn a larger piston.

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you need to work out the ratio of area from the master cyl to the area of ALL the pistons in the brake / brakes it is driving.

for example a 16mm diam master cylinder will have and area of 201mm\2 and if you have 2 calipers off it which are four piston each of 35mm diam the total area is 907mm times no. of pistons = 8 x 907= 7526mm\2

so the ratio is 7526:201 which is 36 to 1

this is just an example and the ideal ratio is anywhere between 22:1 and 27:1

anything higher will feel too soft and the lever will go to the bar and anything lower will feel too wooden and you will have the symptom of feeling no brake till the front wheel locks up

hope thats clear enough

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  • 10 months later...

So how come you can use a Brembo M/C on various different bikes?

And Yamaha Put the same calippers on different models with different M/C's ?

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