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Old 05-22-2002, 08:44 PM   #4
Scooby Specialist
Member#: 16215
Join Date: Mar 2002
Location: In a place with no laws, just "guidlines"
2002 WR WRX wagon


Well what I wrote above still holds. Just now your splitting the car in half.

Basically look at the rears separate from the fronts.

So you would look at the MC size for the fronts just by looking at the front pistons.

Same for the rears

The only thing that can be tuned is feel. You can go to a larger bore for a shorter pedal stroke or to a smaller bore with a longer stroke but firmer feel.

By the way all modern MC are TMC, tandem master cylinder, which is a dual MC in one casting. Of course this means both chambers need to be the same diameter.

It's hard to tell you exactly what size because I don't know your feel preferences. Personally for racing I would rather have a short stroke, low effort pedal (large bore/short stroke) for long distance racing and the firm, longer stroke for sprints( small bore/long stroke). Why? Because on long races my leg will cramp up!

Geez..that thing costs! You must be serious about your motorsports!

This can help you get close to "ideal"

Stopping Force = pedal force * brake pad coefficient of friction * mechanical force ratio * (1/radius of the tire) * brake rotor effective radius

stopping force = weight of car * longitudal coefficient of friction of tires

mechanical force ratio is what you are looking for.

This ratio should get you right to lock up.

Take that ratio and divide it by the pedal ratio.

This is the ratio of mastercylinder bore area and caliper piston bore area.

So say a 4:1 then for a 30cm^2 caliper piston you want a 7.5cm^2 MC or ~28mm bore MC.

For the fronts use the total mass of the car, for the rears use the weight just over that axle. This ensures you get max braking power without locking up the rear all the time.

PLEASE CHECK MY MATH...I have a headache right now.
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Last edited by romanom; 05-22-2002 at 11:06 PM.
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