Brake bores compatibility....

[Justonemorebike]

Mk1 mini being down graded from metro discs to twin leading shoe front and single leading shoe rear.

0.7" bore master cylinder 3/4" bore rear cylinders
Single leading edge front drum compensation valve (original spring put back)
15/16" bore front cylinders.

All new pipes shoes all adjusted to rub then backed off.

Pedal seems to have a long travel almost on the floor.

I will re bleed the system again but am wondering if the above parts combination is actually compatible? Or should I fit smaller diameter brake cylinders?

[Peter Laidler]

Thinking on my feet here, I feel that starting from scratch, there's just too many variables at the moment. You've got to eliminate the first which conveniently is the cheapest and simplest. Bleed the brakes fully to eliminate all of the compressible air. After that it's back to basics - a bit of maths or cylinder diameters based on advice from the forumers. I wouldn't have thought that there are many who have reverted from discs to drums though.

[Oneball]

Have you correctly adjusted the brakes after you bled them, they will have moved around?

[Justonemorebike]

Yes all adjusted and bubble free fluid, apparently I should bed shoes in re adjust a check again as any out of round nss of the new shoes makes it worse. According to my elderly mechanic friend. He also suggested clamping hoses to see if it i.proved things so will try that.

When fully pressed brake pedal is 1/2" off the floor?, I would have expected a little more but its been 30 years since I drove a drum brake mini .

There is about 8mm of free play at the pedal before starting to give pressure.

Any idea what's normal?

[Mini Mad Swede]

You wrote 'All new pipes and shoes' so did you use old drums? They usually have maximum wear size 'printed' on the inside, so maybe measure they arent to worn? Another place that can loose some pedal travel are the brakehoses, especially when putting maximum pressure on them when bleeding the brakes.
Found out the hard way about the hoses after trying to fix the brakes on a -78 Mini.
When left (given up) it stood for a couple of weeks and then the pedal travel felt way better.

Dont know why, but for me Mini's are the No1 car having trouble with brakehoses.
On the other hand its the car I've worked most on, especially brakes.

[Peter Laidler]

Others might disagree but when you press the brakes, you are pressing an incompressible liquid immediately. So there should be NO free play (except for a tiny bit of mechanical wear) Elongated holes in the action of the pedal and pins/forks multiply free play by x5 so rectify this too.

[Craig]

Have you fitted the beehive springs from the shoes to the wheel cylinders ??

Craig