The older minis had drum brakes. These are a definite “NO” if you up the power and are only marginal with the standard 850cc A-series. Luckily my mini came with discs, so it did stop. The easy upgrade for minis it to swap the discs and callipers for an MG Metro Turbo disc/calliper combination. This gives 4 pot callipers on vented discs. The drive flange needs to be moved over from the Metro, but other than that and simple and effective upgrade.

A bit of shopping on EBay found a set of MG Turbo brakes, and were duely bought.

The Z-cars kit provides bike derived discs and callipers, so the rear is taken care of. 

Mini 4 Pot Conversion

What you need:

·        Mini hubs

·        Metro vented discs

·        Metro 4 pot calipers (obviously!)

·        Metro drive flanges

·        Mini CV joints

·        Mini brake caliper bolts (or new ERA turbo ones)

·        Brake line conversion kit

Its pretty straight forward. Split the mini hub/brake apart, do the same with the Metro hub/brake assembly.  Cut the lugs off the Metro drive flanges (I did this with a hacksaw, put with come wheels the flange face may need to be perfectly flat) check that the drive flange fits flush with the wheel. Bolt the flange onto the Metro disc, put the lot onto the hub and tighten up the castlelated nut. Next fit the caliper with the Mini caliper bolts. These are a little sloppy, but people have had no problems in the past. However for piece of mind ERA bolts with the mini thread but a slight shoulder to remove the “slop” are available.

The mini flange would fit onto the metro disc, but the flanges are slightly different in thickness as you can see from the (bad) photo below. This would position the disc in the wrong position relative to the caliper.

The callipers that I bought via Ebay were in reasonable condition but one piston had stuck. I thought about refurbishing the callipers myself, but after some advice from my dad and a bit of thought I decided to just buy exchange callipers – brakes are something you only get wrong once, if you get my drift. Exchange metro callipers aren’t cheap, £47 each!! The callipers will have cost £134 for a pair of 4 pots, ready to fit, which is not too bad value for money I suppose.

The only other thing to buy was brake hoses. The 4 pot calipers were designed for the metro, which had the brake system split so that left rear and one half of each front caliper worked on one circuit and then the right rear together with the opposite halves of each front caliper on the second brake circuit. To convert to operation on a Mini a short hose connecting both halves of each caliper is all that is needed. I bought a Goodridge braided hose conversion kit to do the job.

With new vented discs purchased I put the lot together. It looks the  business.

Next up was the pipe work. I used the orginal pipes as a guide where possible replacing all the front pipe work with new. Again, I replaced the run to the rear, ending in a T-piece ready to split off to the rear calipers. With a couple more braided hoses the rears were connected.

The vacuum feed for the brake servo isn’t obvious on the R1. There are a web of tubes coming of each cylinder manifold. These join together and feed the fuel regulator. I fitted a T piece at the feed to the fuel regulator and took a vacuum pipe off to the servo.

After all that its just a case of bleeding the system. Be-warned, the metro calipers have 3 bleed nipples a piece, so its a bigger job than other cars. I bought myself a bleed Eazi kit that pressurises the system from the pressure in a tyre. Makes the job a piece of cake....I found before using this, the rear bias valve causes problems bleeding the rear calipers. Its also useful for bleeding the clutch as well