Reducing rear braking performance.
Turbo Mini Forums

With a light back end, despite binning the standard brake limiter and fitting an adjustable one my car still has the tendency to want to lock the rears.

Would changing the rear wheel cylinders to increase pedal effort be the 1st port of call, or should I be investigating other issues first?

Regards

James

Edited by minimole23 on 12th Jun, 2017.

bigger bore cylinders on the rear should help i would think

3/4 cylinders should be std fitment on anything after the early 70s I think, that's the largest.

Hmmm, I did change them 10 years ago, but they're just what the parts guy gave me, so maybe worth a shot. well, after a measure.

Edited by minimole23 on 12th Jun, 2017.

Small rears gives less rear brakes. 1/2" is the smalest.

Yeh, you need smaller bore cylinders on the rear to reduce the braking effort.

I've got the 1/2" cylinders on the rear with the standard limiting valve and you can turn the rear wheels by hand when the brakes are applied hard

doh i was thinkingi t was the other way, brain fart!

think I'll check whats in mine at some point.

I don't know if it's technically the best way to do it but can't you just slacken the rear adjusters off on the drums a little?

All that will achieve is a longer pedal.

Are all bias valves the same ? Which one have you fitted ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

What master cylinder are you using? Single or twin?

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Useful suggestions. Seems worth changing the rear wheel cylinders.

Steve, its an unbranded one, and was an improvement, but not quite enough.

Will, its a 1988 Twin Master cylinder.

Dp

Edited by minimole23 on 13th Jun, 2017.

I've never had an issue with locking rears with the same setup you have.

But my car was maybe heavier art the rear, full subframe and I was sat as far back as possible.

Have you filed the leading edge of the shoes? is there any contamination in the drums? Are the hand brake levers free?

These are thing that have caused locking for me in the past; rather than an system issue.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

I may change the brake backplates as they are not straight which won't help. Also handbrake levers are free and everything is contaminant free as went over it all the other weekend.

The rear fact I can almost pick the back up probably doesn't help with the locking.

I would go with smaller slave cylinders.

Ive been looking into proportioning valves of late and they can be a bit of a blunt tool. In my mind you cant make a one size fits all valve as even with adjustable ones you are stuck with the same spring rate in it. There is no tech information on how they behave.

So smaller rear cylinders are larger master cylinder ( if thats an option)

perhaps the back is fine and the front isn't up to scratch ? no idea what the car is just an idea..