Original Cooper S disc brakes VS new grooved discs

[Lord Croker]

It's what we know as the 'Torque Arm Effect' which is what led to the introduction of 4 & 6 pot calipers, greater braking effect is achieved by moving the centres of the pistons further away from the centre of the disc.

[Simon776]

Works Mini's had pads that still used asbestos, do you really want to find some!

Works cars used Ferodo DS11 pads with an asbestos block in the piston.

I used DS11's in my road rallying days and never had any brake issues.

More recently I've used the carbon metallic pads mentioned previously with standard original S discs in the Alps and haven't suffered any brake fade. I see that Mini Spares offer two versions of the S disc in different materials.

[WNX700H]

The torque arm effect ..... yes moving the cente line of the piston outboard will give more braking for a given line pressure but as you move the piston outboard you have to make it smaller in order to fit inside the body casting still . The smaller the piston the less the braking force for a given pressure. On a 7.5" S set up the piston is already about as far out from the centre of rotation as possible . In my experience of using ally calipers they were worse as they flex more and hence you use fluid to do that and increases caliper pedal travel. To get euivalent stiffness from an alloy caliper you need to increase the casting especially in the bridge over the disc which you can do because thats already a tight installation with the iron caliper The std S caliper is pretty much optimal, so fitting ally calipers usually only relieves your wallet.

Correct brake balance is key and whilst the rears do far less work on a mini you need to get as much utilisation out of the rears as you can so that you minimise the heat issues in the fronts whilst still avoiding rear lock before the fronts in order the vehicle remains stable for the road. Also careful choice of friction material is key if you have upgraded front materials and crappy rear stuff the rears fade out early and all the work is done on the fronts making the heat dissipation issue worse. You need a rear material that has similar fade characteristics to the fronts so your nominal balance remains constant and you are getting as much utilisation our of the system as possible..... on this set up every little bit counts.

Brake system design with Girling for 25 years.

[Ratkiller]

So i'm going to bite the bullet and buy 4 pots.
I'm looking at these:
http://www.minispares.com/product/Class ... .aspx|Back to shop

What are the correct metallic pads to use with these?
And can I still use my stock MK1 resivor?

[Smiffy]

You don't need the expensive carbon metallic pads with these, just running black stuff pads in mine and besides the dust there fine.
If your gonna stick with the, standard cylinder I'd advice at least fitting the extension tubes. As the four pots displace more fluid.

[ianh1968]

I'm looking at these:
http://www.minispares.com/product/Class ... .aspx|Back to shop

It's no wonder people put calipers on upside down, look at the photo...

[Vegard]

I'm looking at these:
http://www.minispares.com/product/Class ... .aspx|Back to shop

It's no wonder people put calipers on upside down, look at the photo...

It's one of those new style calipers, where you open the valve and the air just pours out...
I remember a long time ago, then the cast calipers where the ones to use, (aluminium) and billet inferior. Now, noone does the cast ones any more, so subsequently billet is far better

[andy1071]

I should have been following this thread, but somehow it slipped below the radar...

As a ex-AP Racing person, can I make a few comments?

The brakes fade because of the amount of heat (-energy -you're removing momentum from the vehicle) you put into them. -Changing the pads, discs or calipers does not change the amount of energy (heat) you are generating.
-As stated, when you change the caliper or discs you are changing the characteristics -typically more heat capacity, or better heat radiation / convection. So you (hopefully) move the fade / overheating point out of your operating range.

The friction of the different pad materials is generally similar -but it tends to be at different working temperatures or temp ranges. -If you do find some old DS11 pads, I wouldn't recommend them for road use: -they really need lots of heat in them to start working (at ambient temperatures, they have lower friction than standard pads -working temp range remember..).

Grooves on the disc face help to clean (de-glaze) the pad, and vent gases, as stated: but only if the pads are prone to glazing / de-gassing (this depends on many factors: -heat input, material etc). Usually 'road' spec pads don't need them.
But the other effect of grooves, which is beneficial, is that they present an edge to the pad. This generally improves the initial 'bite' of the brakes, which can give the feeling of improving the brakes. -Drilled discs can give the same effect.

While drilled discs reduce the mass of the disc (hence the heat capacity), the increase in surface area (the area of the sides of the hole) increases the radiation / convection. -But, you need to take the heat away -which is always a problem with small, typically enclosed, wheels. Brake ducts help.

It was common to put asbestos blocks in the pistons. -To insulate the piston and slow the heat transfer to the fluid.

Racing fluid has a higher boiling point than normal fluid, but is more hygroscopic -it absorbs moisture faster. So you need to change it more often. -I wouldn't recommend it on a road car. -But if you only drive in the summer, and change the fluid every season, you may be ok...

Most (all?) car of the '60s and '70s will fade their brakes of a race track -and on a mountain descent with continued brake application -there is not enough time between brake applications for the heat to dissipate. (And in a mountain descent, the rear brakes will be contributing less than when braking on the level).

If the brakes are fine for all your 'normal' driving, and you only had a problem on one mountain descent, I would recommend staying with what you've got, and remembering to compromise your driving style on the mountain next time (this is the cheapest solution!!!). But if you want new calipers, go ahead: it's your money

Modern asbestos-free pads have as good as, or better, performance than the old asbestos pads (but remember the dust from modern pads is still dangerous! -All dust and fibres are not good to breathe...). So I'd be happy to use appropriate modern pads. -Though they can be more aggressive to the discs, and wear them more.

[pad4]

Well Said and I for one totally agree with you although im sure some wont

pad

[Nevsmini]

Looked at this tread today and saw 5 pages about breaks ????? Pity Andy did not answer first but then they would be no entertainment value !