Article on The Internet Mini Encyclopædia
The metro uses a twin circuit. One circuit does front only (2 pots). The other does 2 pots at the front and the rears as well. Therefore, unlike Mini systems where you lose diagonal wheels or alternatively either the front or rear set, failure on the Metro always keeps some braking at the fronts.
Caliper bolts on Mini Hubs ERA parts are required
Despite the fact "they fit and do up" the existing Mini caliper bolts ARE WRONG for fitting Metro Calipers to your exsiting hubs.... Somerford Minis and others produce shouldered bolts ( bigger diameter but same thread as the Mini hubs), these were fitting to the ERA Turbos which used Metro calipers as standard on 12" wheel mini hubs (added by FB 21 March 2004 having been driving around for 4 years with the wrong bolts... done up REAL TIGHT!!!!)
When upgrading calipers to 4 pot Metro, beware there are two kinds, Lockheed and the rarer ATE.
The ATE caliper does not have the wiper seal on each piston as the Lockheed has, but instead has a thin diaphragm dust cover held in place by a metal circlip.
Getting seal kits for this type is very difficult, and prices can be TEN TIMES the price of lockheed seal kits.
Additional notes added 01 01 2005
Q: Are metro drive flanges 100% needed?
A: You can use mini flanges, but they are thicker and AFAIK this will move the disk towards the engine slightly and can rub somewhere, not sure where. I used metro flanges for my 4pots. Removed lugs with AG and refaced them up on the lathe at work. If you use mini flanges then the disc bolt holes need enlarging from 3/8" (9.5mm) to 10mm. The bolts need to be 10mm for the metro (metric!) discs. The mini assemblies use imperial 3/8 and metro uses metric 10mm for disc and caliper bolts.
Q: Are vented and non vented flanges different?
A: No, not AFAIK
Q: You do need special caliper bolts metro mini don't you?
A: (see above) Yes, the mini hubs have 3/8" caliper mounting holes and the calipers are 10mm so will be 'loose' if fitted with mini bolts. Minispares sell "ERA" caliper bolts. My setup is typical of a mini 4pot setup. I used... Mini 8.4" hubs Mini 8.4" CVs Mini 8.4" hubnuts Mini 8.4" disc bearings Mini 8.4" disc balljoints Metro 4pot calipers Metro vented discs (grooved/xdrilled) Metro flanges (delugged) Conversion hose from minisport Pretty much the best braking setup for a road mini!
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