Quote:
Originally Posted by 97 SL320
Some master cylinders have bore sizes cast on the housing. One that is marked 19 / 25 is a stepped bore, 19 mm / 25 mm .
Stepped bores ( along with some internal valving ) are usually used to provide high volume / low pressure to bring caliper pistons out rapidly then switch over to high pressure / low volume for actual braking. If you had a large bore only, the peddle would be very hard, if small bore only peddle travel would be very long. This system is sometimes used on industrial equipment ( like forklifts ) to provide power braking without any " power unit ".
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Using the lower limit data in the FSM (see post above) and a bore diameter of 19mm I reckon the force required is =>
Force = Pressure X area
area = 2.83e-4 m^2
Pressure = 50 bar = 50e5 Pa
Force = 1417 N ~ 145 kgf ~ 320 lbf
I don't know if that sounds about right - do you?
I realise that this isn't the full story - there's a brake booster - and then the mechanical advantage of the brake pedal =>
BRAKE MATH: CALCULATING THE FORCE NEEDED TO STOP A CAR: Brake and Front End
More data needs to be found - if this is of any use to the OP!