34 replies to this topic

[sonikk4]

Cooperman would be the best to advise about pads.

[sonikk4]

I'm not sure, but I seem to remember that if going to 'S' discs and 'S' master cylinder, you might need a different pressure relief valve for the rear brakes.

Whats the reason for that please??

[Artful Dodger]

The 7.5 set up was designed to use a servo. The S cars had them and the GTs had them. I'd use a servo:P

Ahh but what if you want to keep it looking standard though. I have been recommended on here that if you are not using a servo to go for the Cooper S master cylinder AD.

fair enough!

il be honestm my system is a late split system master cylinder, (rears on a bias valve and fronts no limiter valve) GT servo and 4 pot 7.5 calipers. when i plumbed the system up i put it up on the brake roller tester.

Without the servo (no engine, no vacumn etc) in use the brakes performed very well! nearly locked up!

I'm not sure, but I seem to remember that if going to 'S' discs and 'S' master cylinder, you might need a different pressure relief valve for the rear brakes.

dont you mean rear drum cylinders? thats how they were 'limited'?

[Jared Mk3]

I'm not sure, but I seem to remember that if going to 'S' discs and 'S' master cylinder, you might need a different pressure relief valve for the rear brakes.

With regard to pads, it depends on how hard you will be driving. Standard 'S' pads are quite good so long as they are original spec. EBC Green are good for road driving and for competition the Carbon-Metallic pads as supplied by Mini Spares are absolutely fantastic.

So would I need to change the pressure relief valve or change to different wheel cylinders?

With standard spec discs, would Green Stuff pads be good?

[Cooperman]

I'm not sure, but I seem to remember that if going to 'S' discs and 'S' master cylinder, you might need a different pressure relief valve for the rear brakes.

Whats the reason for that please??

Just checkin, the regulator valve is a 21A1774 on all Mk.1 & Mk.2 and all Cooper 'S'.

Mk.1 'S' had a 0.625" rear wheel cylinder, part no. GWC1101, but it seems that the later 'S' had a 0.75" rear wheel cylinder GWC1102.
The Mk.2 Mini had the 0.625" rear cylinder except very early 850 which had the 0.75" cylinder as had the 997 Cooper, whilst the 998 Cooper had 0.625" ones.

Confused as to why, well I certainly am.

[sonikk4]

My Clubman is a 998 so will have to have a look at the slave cylinders this week.

[Artful Dodger]

i cant see any other regulator valves for sale, so they must all be the same. anyway, to change it all you would need to do is alter the spring rate of the spring inside it.

and as for the wheel cylinders, could it be because of the different master cylinders, and possibly the different ratios of pedal to master cylinder and master cylinder size?



bleedin BL!

[sonikk4]

Well if push comes to shove i will see what happens. Either it will work or it won't.

[Cooperman]

All brake master cylinders were 0.70" bore. The early 850 cars had GMC153, then they all had the GMC102 up to the Mk.2 and part way through the Mk.2 they went to the GMC171.
The Cooper 'S' had the GMC172 as did the 1275GT up to 1974 when it went to diagonal split brakes.
But the 997 Cooper had 3 different master cylinders, all with 0.70" bore, GMC103, GMC104 & GMC171. 998 Cooper had GMC171.
The 'S' master cylinders had a greater fluid capacity.

No wonder BMC never made any profits!

[Jared Mk3]

So the only difference between the standard one like I have and the "S" item is the fluid capacity?

[Cooperman]

Looks like it.

[JVA10L]

I have used the small capacity master cylinder with 7.5" S brakes and no servo and it worked fine but I did have an adjustable bias valve for the rears. The larger tank is there because the fluid level drops as the pads become worn so make sure you check the fluid level often. The original master cylinder was actually 0.75" bore but they were only fitted to early 850's so yours will be 0.70".

[Ivor Badger]

I have used the small capacity master cylinder with 7.5" S brakes and no servo and it worked fine but I did have an adjustable bias valve for the rears. The larger tank is there because the fluid level drops as the pads become worn so make sure you check the fluid level often. The original master cylinder was actually 0.75" bore but they were only fitted to early 850's so yours will be 0.70".

So I can take it that the adjustable bias valve was a finer adjustment than oiling the brake shoes?

[tiger99]

Very amusing! Oiling the shoes indeed....

I don't think that you will need to change the pressure limiter, as the maximum pressure it allows, which should not quite allow the wheels to lock, has nothing at all to do with the front brakes. However, at lower braking levels, there may be a mismatch between front and rear, which should not cause problems, as it is only rear wheel locking which is problematic.

I would prefer to reduce the risk of locking in the wet even more by using the 0.625" rear cylinders. 0.75" is too big.

Ideally you would use an adjustable pressure ratio system, or a balance bar and twin master cylinders, not a limiter, if they are legal where you are, to optimise it properly.

Edited by tiger99, 11 March 2013 - 10:26 PM.

[Jared Mk3]

So I could get away with refurbishing my current master cylinder and adding one of those extension pieces currently available? Like so :

http://minispares.co...px|Back to shop