difference between rear drum and disc brake master cylinder

[93patrol]

hey guys I am looking to replace my brake system as the peddle is a bit funny really have to really stomp hard on it in reverse to stop and get a bit of brake fade, i have rebuilt all 4 calipers and i was going to replace the master cylinder and i was wondering if anyone know the difference between the disk/drum M/C and the disk/disk M/C* as it doubles in cost to get one to the other?

cheers
Shane




* master cylinder

[threedogs]

Might be the amount it can push{volume} and pressure it has

[Lieney]

Threedogs is basically correct.
Effectively, I would find the specs / volume of each master cylinder first. That will give you an indication as to the compatibility, OR
buy a re-build kit for the one you have. PBR make all sorts of kits and most 'common' car stuff is ok. - CHEAPEST OPTION, if your m/cyl internal surface is okay
To answer your specific question directly I can't; but I do hope I can give you some info to think about and maybe you can work it out.
The diameter of the pistons, the piston travel and pressures capable within the master cylinder, have a set ratio with that of the pistons in the wheel cylinders / callipers.
This is to allow the required force on the brake pedal to transfer pressure to each wheel cylinder or calliper accordingly to apply a the force, thus braking.
You may be able to request specs to confirm piston size & travel of the primary and secondary piston within each type of master cylinder.
Then you could work out how much fluid each type moves at full travel and what sort of pressures are available at the outlets when 'X' force is applied to the pedal.

Design and specs of each m/cyl and w/cyl / calliper ensure the basic 60/40 split forces front to rear.
Swap things around without checking first, and you end up with REAL GOOD, or REAL BAD, front or rear braking.
Brake callipers generally have a larger piston surface area, therefore will apply more force to the pad with 'X' pressure. However, the distance they move is less than a brake shoe (generally). Forces achieved here are fairly high.
A wheel cylinder, and there are so many and varying types and sizes around, are 'generally' smaller in surface area, so to achieve the same force you would need 'x' pressure times something else. The pressure required to achieve the same force is somewhat more; 'generally speaking'
Check out a re-build kit, or find someone else who has done the swap, or take on the mathematics challenge!!

[93patrol]

think imight go see a brake guru in town see if they do an exchange one that way i get a good rebuilt one and the right one for the ute.

cheers for the info Lieney i cant be bother with the maths though it would hurt too much

shane

[BigRAWesty]

Sounds exactly the same as an issue I had, and it was a vacuum leak.

Kallen Westbrook
Owner of
Westy's Accessories

[93patrol]

yeah i ll check that out as well but i have to get back off my brother first i borrowed his car for a bit to take my kid around as the ute is a ute and the missus doesnt want me to put a booster seat in it.

i ll sort the brakes out and then you watch something else will go like the steering will start to wobble haha, such is life

[BigRAWesty]

yeah i ll check that out as well but i have to get back off my brother first i borrowed his car for a bit to take my kid around as the ute is a ute and the missus doesnt want me to put a booster seat in it.

i ll sort the brakes out and then you watch something else will go like the steering will start to wobble haha, such is life

I know how you feel.. just sorted brakes and clunks, vac pump leaks and vacuum leaks, now death wobbles getting pretty serious and another $600 going, going... Gone..

Kallen Westbrook
Owner of
Westy's Accessories

[93patrol]

yeah i think i will slowly but surly replace all bushes and hoses and everything else except the chassis, body, rims , diffs and motor unless its to bolt a turbo on

[BigRAWesty]

yeah i think i will slowly but surly replace all bushes and hoses and everything else except the chassis, body, rims , diffs and motor unless its to bolt a turbo on

Funny that's my plan to.. should be a new car once done

Kallen Westbrook
Owner of
Westy's Accessories

[93patrol]

think it be about as much as a new 4.2td patrol when done about 50g. hahaha