[A8D2driver]

Just managed to squeeze a digital measuring caliper around my disc with the wheel on. Can do it at a small window just above the brake caliper where the back plate is not obstructing. Its 21.5 cm - evidently 22cm when new. Diam must be 280mm - hard to judge with wheel on. Problem is all the factors selling right rear calipers quote 1999-2002 A8 3.7 and 4.4Q, but then state 43mm piston (OK) but 20mm max disc size (not ok). All except Euro car parts whose registration based system which I suspect finds the chassis number has the 22 mm disc size braks calipers but at twice the price of the factors with the 20mm size (£150 after return of unit). As you might expect not in the 30% discount items on Euro car parts. Did get the discs and pads from them . Even more confusing On 'E bay' even 'Euro car parts outlet' comes up selling the 269mm discs but 22mm thick. Looks like just judging the thickness isn't enough. Oh no - Im going to have to take the wheel off and try and measure the diameter in situ to within the 11mm difference before I can order the parts. Trying to source a repair kit is even more interesting but looking at the diagrams to strip and rebuild it don't really feel I should try this. Have done the fronts before but the screw for the handbrakes mechanism looks like it makes it much more difficult. Probably going to be new LH and RH units from ECP. Cheaper than a gearbox though. Keep checking the mass air flowmeter is giving correct load and flow rate readings using VaG com, (even lite will do this dynamically) if you want to avoid a new gearbox on 1999-2001 3.7s. I change my MAF every two years after my wife's 3.7 needed a gearbox after 15,000 miles because of this problem.