Slave Cylinders..
Turbo Mini Forums

Let me get this right

My rear brakes are locking up too easily (even with a limiting valve), so......

Small slave cylinders= less braking????

Or the other way around??

Yep. Just swapped to smaller brake cylinders for the exact same reason!

smallest cyinders available are 1/2"

Part no's GWC1126 or (i think) BWC3097

They are deffo 1/2" though

Matt

Oops, double post!:$

Edited by bodgeit on 2nd Jun, 2007.

top call here chaps i've had this prob, offto min-its for some cylinders :) maybe new brae shoes too it the mini is a lucky lil thing

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Tom Fenton says: I have it all, make me an offer

Hi,
I would have though the smaller cylinder would give more braking.
You've got the same amount of pressure to the cylinder but the smaller area will cause more pressure on the shoes?
Cheers,
Gavin :)

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Smaller Master cyl = more brake
Larger Slave = more brake
Regards
Dave

oh fork, now im confused

If fitted a 7/8th inch master cylinder (bigger than std) and now my back brakes keep locking up on me

Master cylinder sizes won't help. A bigger / smaller master bore will STILL have the same bias at the rear comapred to the front - you'll just be pushing the pedal harder / less.

You need to get smaller slaves, or put a few paving slabs in the arse end of your mini. I suspect your problem is partially due to a lack of mass LOL

smaller it is.

If you have a small master cylinder and a big one, the big one should go back as it gives less force, and the small one that gives most force should go to the front.

Its just a matter of reversing the formulas used here to calculate the travel or force of the brake lining/cylinder

Edited by miniminor63 on 3rd Jun, 2007.

urghhh i hate brakes!!!

Right definately smaller cylinders! Stupid lightweight cars

I seriously doubt it!

you do NOT move (much) fluid in a brake system. You transmit pressure. At least as long as there are no compressible fluids in the system. A smaller master cylinder will give higher pressure difference.

I seriously doubt it!

Smaller slave cylinders will exert less force for a given fluid pressure than larger ones.

Pressure is pounds of force per sqare inch of area. Less area, less force.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I seriously doubt it!

force = pressure x area.

If you have a master cylinder with a piston area of 1 square " and apply force of 100 kg to it a slave cylinder at the other end of the line with an area of 1/2" will provide half the force but twice the travel, if you swap the slave to 2" area it will travel half the distance but provide twice the force.

There is a balencing act against pedal travel though, if you have too small a master or too large a slave the pedal has to travel to far and ends up bottoming out, or working in an inefective part of its travel where the ratio is decreased and feeling crappy.

Alternativly think of it in terms of levers, you want to push down on the long lever to give more lift at the small lever.

Edited by Joe C on 3rd Jun, 2007.

Paul, It is all about line pressure and not fluid transfer.
Imagine the following.
2 master cylinders A & B
area of A is 1 sq in.
area of B is 2 sq in.
you apply 60 lb to the pedal (piston)

pressure down the brake line is:-
A 60 psi
B 30 psi
therefore a smaller Master Cyl gives more effort at the brakes

Reverse the above logic at the brake end and a larger slave gives more effort at the brakes.

Regards
Dave

Everything Ive ever read, and all the racing specialist Ive ever talked to say put on as larger master cylinder and smaller wheel cylinder. They are the professionals - they know what theyre talking about from theory and practice. Im quoting what they have told me which did work for me.
How can their word be disputed?

Paul

I seriously doubt it!

I dont know, but they are

It is intuative to think a large master cylinder will give more pressure but it is wrong. A basic knowledge of Hydaulics will tell you that it is wrong.

The largest (practical) master cyl / small slave cyl is the best way to achieve a short pedal travel assuming it gives the required line pressure. This is due to fluid displacement.
Fitting a smaller master cyl to increase braking will always give a longer pedal travel.
Similarly increasing the diameter of wheel cyl /caliper piston will increase braking force but it will increase pedal travel.
Why do you think four and six pot calipers are used? ( to increase area at the brake end) ...(LINE)Pressure x (PISTON)area = (BRAKING)force.
Hope this will clarify it a bit more.
Not trying to sound patronising but if Kad, and all the others are telling you different they are WRONG!!!
Regards
Dave