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Mk2 Cooper rear brakes (2 replies)

Edington
5 months ago
Edington 5 months ago

Well I'm back after some time away and realise I've had my Cooper for nearly 5 years and its still not finished! So I've given myself a good talking too and while I wait for the shell to get its final paint I've been doing all the other re-build bits. This leads me to ask if anyone knows the correct diameter of the rear brake pistons? The ones that were on it were 0.75"dia but as it was previously used for rallying with built-in spacers on the brake drums I'm not sure if this is original spec.

Daz1968
5 months ago
Daz1968 5 months ago

They should be 5/8 rear cylinders and master cylinder is also 5/8 bore. The rear brake shoes should have a small spacer built in I think about 3/8 bit these are nla new. I will be fitting genuine mini fin rear drums with a separate spacer on my car. I would try to get a correct master cylinder if yours is 3/4 as it really makes a difference.

Edington
5 months ago
Edington 5 months ago

Thanks DAZ, interesting. I thought I read somewhere that they were changed to 0.75" diameter sometime in late 1969 (mine is a July 1969 Austin Cooper)! On another point I was in the progress of buying a pair of new rear brake quadrants that take the brake cable through 90degrees on the swing arm and was looking at MiniSport which provides two sorts one for wet and one for dry suspension. My cooper is as original as I can make it so will be going back as wet. I don't really understand why there is a difference. Any thoughts?

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