Four pot calipers for Classic Mini:
KAD manufacture in total three different Mini 4 pot calipers according to their offset from the centre of the disc. There is one size of caliper to suit 12 and 13" wheels (marked "12") and two sizes of 4 pot caliper for use under 10" wheels using either 7.5" (marked "M") or 7.9" (marked "10") diameter discs depending on the type of 10" wheels fitted.
Most of the modern pattern wheels (Minilite, Minilife, GB alloy, 100+, Spectrum, MB Racing, Revolution, Revolite etc) have sufficient clearance for the 7.9" disc to be used which non standard size achieved by machining down an 8.4" (part GDB 90806) 12" wheel disc. This mounts to the late type Mini drive flange (21A 2695).
The Cooper S steel and reverse rim 10" wheels, Mamba and Magnesium Minilite must use the smaller disc size (7.5) which can be either the 8.4" disc machined down with late flange or Cooper S disc and flange (with our 'S' fitting kit of spacer washers and longer bolts). Many older types of wheel fall into this category also and in some cases wheel spacers must be added as these wheels were often initially produced to fit over drum brakes.
All of the calipers can be used with vented discs either as supplied (as a vented type caliper) or by the retro-fitting of the spacer kit and longer bolts, our calipers are designed to mount these to the late Mini flange by drilling the mounting holes from 3/8" (9.52mm) to 10mm. There is no vented option available for the S flange.
We do not use the Metro flange due to the upstanding lugs in the centre of the flange which prevent many Mini wheels from fitting. If you have bought our calipers and are wondering why you cannot make them, you should establish that you car has not been fitted with Metro flanges as there is an offset difference in the flange which will be causing your problem.
When fitting vented discs not supplied by KAD, the inside of the disc bell must be machined to provide clearance over the hub oil seal. The final dimension for the thickness of the face that the drive flange bolts to is 0.660". In 90% of cases the vented disc will now touch the steering arm where the arm forging bulges out around the mounting bolts, here it is necessary to either file or grind the bulging portion to achieve clearance of 2mm, there is plenty of meat in the arm at this point so strength is not a problem.
The hub/uprights are the same between the late Mini and the S type, but the drive flanges are different so its not possible to use the late flange with the S disc or vice versa.
Six pot Type A Calipers for Classic Mini:
These calipers offer more universal fitting possibilities than the four pot as they are a radial mounting caliper and can be spaced out radially from the disc centre line. They are supplied with alloy spacer washers which allow fitment to disc diameters from 7.9" minimum to 8.4" maximum. There is sufficient length in the pistons to allow their use on either vented or solid discs but if they are used on solid discs, brake pad wear must be monitored as it maybe possible for the pads to fall out if the pads are allowed to wear down to the backing plate.
If you are running 13" wheels in competition, a big disc conversion is available which uses the type B six pot caliper with a 265mm x 18mm 2 piece disc assembly.
The six pot calipers are not fitted with dust seals as they are primarily intended for racing, if you are using them for a road car, you must make sure that the area around the pistons is kept clean of brake dust and road salt etc as the piston bores will corrode leading to pistons seizing and early caliper replacement.
Plumbing and bleeding
(This is not a lesson in fitting brakes, if you are that unsure of what you are doing please ask yourself if you would be better to get an experienced person to fit what is one of the most safety critical parts of your car.)
All calipers have a single 3/8 UNF fluid feed same as the standard Mini.
Bleeding the calipers should be easy since the fluid passage ways have been designed not to trap bubbles of air, the calipers are not handed and bleed from the top bleed screw (obviously). If you are experiencing trouble achieving a good pedal try bleeding the master cylinder first then the calipers as the job is easier if the master cylinder is pumping fluid and not air.
Bleed screws are small delicate things that need to be treated gently, if they still appear to be weeping fluid and you have tightened them already, resist the temptation to keep tightening until they shear off. Instead, loosen and tighten them 6-10 times, what this does is to form a nice seat in the caliper body and they should now seal OK. Tightening torque should be about 4 lb/ft only. Caliper mounting bolts should be tightened to 25-30 lb/ft with a thread locking compound.
In cars with a single master cylinder, there may also be air in the lines to the rear cylinders so we have found it useful to jack the rear of the car to assist in expelling bubbles trapped in this pipe run.
When fitting the brake pads to either of the 10" wheel calipers, the bottom corners of the inner brake pads must be cut as they interfere with the hub mountings as the caliper is pitched closer to the disc centre line.
Care of calipers.
Regular brake fluid changes keep water out of the fluid and calipers reducing corrosion from the inside and preventing brake pedal fade (spongy feel when hot). Clean the outside of the calipers and around pistons with warm soapy water or proprietary brake cleaner to remove the build up of brake dust which is itself very corrosive. Allow the calipers to dry before wiping over with WD40 or similar. The caliper seals are made from complicated rubber compounds which are attacked by certain chemicals, it is best to avoid spraying non recommended fluids in around the piston area. Steam cleaners are also not recommended in this area.
Wheel clearance templates:
These PDF (Adobe Acrobat) files can be downloaded, printed out full size and glued to card backing. The profile can then be cut out and tried into the wheels to ascertain if there is sufficient caliper to wheel clearance.