Brake Cylinder Bore Clearances
Turbo Mini Forums

Does anyone know what the clearance is between the rear brake cylinder & the piston? and further does a half inch rear brake cylinder have an internal bore of exactly 0.500 inches or is it more like 0.503 inches to allow for the piston bore clearances?

Edited by Rob H on 1st Apr, 2010.

Sorry Rob, not much help, but IMO there can only be a few thou in it.

New cylinders are only about £8. Can't you just mic one up ?

I'm assuming you don't intend using it for brakes ?!?

Richard.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

I always thought they were a sloppy fit like near .5mm and any play taken up by the seal. However dobt have one to hand to measure :(

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

I can't answer for definate as I've not measured one.

However, normal engineering convention is to make the hole an exact size and put the variation for clearance or interference on the OD of the mating component.

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."

Cheers, I'm toying over machining up some alloy ones to save a bit more weight off the car, god knows if it'll work or not.

Usually you need at least 0.05mm to allow oil enter the clearance. As here the goal is to prevent oil passing I'd say you need at most 0.05mm.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Interesting Rob.

With an ali piston and a cast iron cylinder, will it be more susceptible to galvanic corrosion between the dissimilar metals ?

I only ask as we've had a number of problems with actuators on marine turbines where the ali pistons had seized when in long term contact with CI and hydraulic fluid - caused by moisture contam.

Richard.

Edited by turbominivanman on 2nd Apr, 2010.

Minivanless, but reluctantly happy living with the decision. There'll be another one day.
http://www.youtube.com/profile?user=minimadmotorman#p/u

I was thinking of going for an aluminium piston and an aluminium cylinder, the later is going to push the limits of my tools but I think I can do it.

I was thinking of going for an aluminium piston and an aluminium cylinder, the later is going to push the limits of my tools but I think I can do it.