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Master cylinder piston travel
Slimy38 - 24/8/20 at 07:11 AM

How far does the piston on a master cylinder need to travel? I can understand it being a lot smaller than pedal travel, but how far is it?

I also expect it will be different depending on whether it's for brakes or a clutch?

steve m - 24/8/20 at 11:15 AM

My floor mounted setup, the brakes travel was about 15mm,
Clutch to the floor was around 25mm

steve

Mr Whippy - 24/8/20 at 12:24 PM

Stick it in a vice and push a screwdriver in the end till it bottoms out. There's no one size, they come in all sort of sizes. If you get the part number off the side and stick it in google you may be very lucky and get a spec but I've never seen that and would much prefer to measure it myself.

Slimy38 - 24/8/20 at 01:59 PM

quote:
Originally posted by steve m
My floor mounted setup, the brakes travel was about 15mm,
Clutch to the floor was around 25mm

steve


Perfect, that's the sort of travel I have at the moment, thanks.

quote:
Originally posted by Mr Whippy
Stick it in a vice and push a screwdriver in the end till it bottoms out. There's no one size, they come in all sort of sizes. If you get the part number off the side and stick it in google you may be very lucky and get a spec but I've never seen that and would much prefer to measure it myself.


My first thought was to see how far it can physically travel but it ended up going quite far, a good couple of inches from circlip to base. That would equate to maybe 8 inches or so of actual pedal travel!! But then it occurred to me that the pressure of the circuit would prevent it going to full travel (under normal circumstances).

The clutch is a bit different as there would be very little resistance and so it could travel further. And that ties in with the 15mm and 25mm travel that Steve describes.

It sounds like I'm in roughly the right place though, I can do slight tweaking once everything is in the car. Thanks both.