To be honest, I don't notice a huge difference in the stopping power, after an hour stint, my leg isn't tired...

There is a more confidence knowing that the pedal will be there every time. They never seem to fade, even under race conditions, hour after hour. I have seen racers cook their brakes in a vintage race that is only 1/2 hour, which is what influenced my decision, that and the fact that my Stepdaughter races and I want her to be as safe as possible out there.

Sean how much better are the 4-pots than the S calipers?  Overkill for street?  I'm not even boosted and I'm content.

Te Lemons car has a GMC227 master, Alloy 4pot front brakes and we have the 5/8" cylinders in the back, this setup drags everything down from over 160km/h without swapping ends. The brakes are fantastic and very predictable.

The fixed pressure limiter works even better as it turns the rear brakes off preventing locking.  Mine is a later car with the stepped MC.

Thanks all .. lots of excellent advice.  Much appreciated!

When we added S discs to my son's 1976 Mini 1000 with MG Metro 1275, we did not down size the rear wheel cylinders.  Two spins on St. John's in Port Moody in the wet in early morning traffic on his way to university and we put an end to that quickly, installing 5/8" cylinders.  Fortunately, he did not hit anything either.

Stock ramp/ball bias valve, wheels 10"x5" 100+ with Yokohama 165/70 GX501s.

I will not drive a Mini with disc brakes and the larger rear wheel cylinders without some brake limiting solution to eliminate the possibility of rear wheel lock up.  The ends swap very, very quickly!

Alex, what rear limiting valve do you have? I'm talking early cars here, 1961-1978, that just got a fixed pressure limiting valve.
Inertia valves or proportioning valves may work better, considering Rover Coopers all had bigger rear cylinders (I think).

I've got S-discs and ¾" cylinders at the rear.

Stand on everything (and I did last week in the damp) and the fronts lock but the rears don't.
The advantage of locking the fronts only is that I didn't swap ends, and when I came off the brakes at the last second I went in the direction the wheels were pointing.

I bought a pretend 1275 S for my wife a few years ago. The PO had fitted S front discs and kept the 3/4" rear wheel cylinders. All was well until one day in the rain on the F3 freeway @ 110kmh, I had to do an emergency stop. Rears locked, car swerved, it was real scary but fortunately I hit nothing.
I went home and fitted 5/8" rear cylinders, no further problems.
All disc braked Cooper S and Clubman GTs built in Oz got 5/8 rear cylinders, and all the drum braked Minis got 3/4".

If you think bigger rear cylinders are fine with discs, go jump HARD on the brakes in the wet, or on a dirt road and see what happens...

Yes, adjust the rear shoes until they just rub.. Do the adjusting with the rear wheel off the ground.  Tighten up the adjuster until it rubs, then with the handbrake off, spin the wheel hard and yank on the cable to stop the wheel.  This will centralise the shoes and may allow more adjustment.  Repeat as necessary.  Once the shoes are adjusted then adjust the cable where it attaches to the lever.

Also check that the quadrants that the cable passes through at the front of the trailling arm are the right way around.  The quadrants are assymetrical and can be installed back to front.  If so, the quadrant may jam against the trailling arm when the lever is pulled up..  The section of cable in front of the quadrant (ie that attached the handbrake lever) can be bar taut while the rear section (that controls the shoe) may be quite slack...

Cheers, Ian

Originally a 998 Cooper, I swapped the 7" discs for S.  And just as above one of the rears locks up.  However I've not yet had to panic brake so hard as to swap ends.  In the rain the fronts lock as expected.

When adjusting the rears do you want the shoes just barely touching and slowing down the wheel, as they do on the fronts?  I will guess you guys will say yes.

However as Hunter says I should still do 5/8 cylinders at the next change... what a helpful tip.

I've never been able to get my parking brake to work continuously well.  Even though the cable tension nuts are adjusted tightly enough to allow you to pull the lever up only three or so clicks, the car will still roll.

Any local speed shop can sell you a brake bias adapter that you plumb into your brake lines. They are usually around $39.00.

this gives you ultimate control of your brakes. We use them on all our cars that we autocross. If you bring the brake line into the car you can adjust it from inside.

Discs run different size rear cylinders.

Deb

Fronts locking is not a problem at all, and I wouldn't worry at all.

Rears locking however is an entrance to a whole world of hurt...

Actually the 'end swapping' can happen in the dry. It happened to me twice at signal lights until I figured out it was a defective brake bias valve. Its frightening. Luckily nobody else was around, so there was no damage other than soiled pants. 

Spitz is kinda correct ..but it works the other way 'round...

The extra stopping power at the front causes more weight transfer which means the rear tends to lock up more often.  So, when S discs were installed a smaller rear wheel cylinder was also fitted to reduce rear braking effort... Some cars (all of mine) have a rear brake limiter device bolted to the rear subframe.  I would check this if you feel that your rear brakes are not doing what they should.

Personally, I've never(sic) bothered with the rear cylinder mod..and have not suffered any issues.

The bottom line is that you don't want the back to lock up before the front.. some racers even disconnect the rear brakes to prevent nasty suprises.

If the fronts lock before the rear then all is as it was intended...

Cheers, Ian

Do you mean the rears lock up??  Because that is the principal issue when moving from drum to discs up front.  When the rears do lock up you can find yourself in a spin swapping ends in the wet or on a very dusty or otherwise slick road surface.

Switch to 0.625" (5/8") diameter rear wheel cylinders.  Or install a brake bias valve in the hydraulic system.  The former is easier & cheaper to do.

I think the norm is to switch the rear wheel cylinders

I've upgraded the front brakes on my 1966 Australian Mini, with an S disc conversion kit.  They're a great improvement, but they're now so much stronger than the rear drum brakes that I find they lock up under panic stopping, with the rears being ineffective.  Is there any way to balance front and rear more evenly?  Any suggestions most welcome!