I was looking at the Audi A3 TDI specs and it looks like the front brakes are 312 mm in the front and 280 mm in the back. The diameter is the same as the VW GTI brakes but what about the width and calipers?
I don't have the part numbers for the 2010 but for the 2009 models, the front and rear VW GTI caliper and rotors part numbers are the same as the Audi A3 gas model. I assume the Audi A3 TDI gets the same rotors as the Audi a3. 312mm x 25mm in the front.
The rears are also the same- 286mm x 12mm rear rotors.
Thanks for the tip, I will add it to the Audi A3 checklist. Both cars are FWD but the A3 is automatic and 4 door only so it weighs about 255 lbs more than the Golf TDI automatic. According to VW's site, the golf TDI (doesn't say 2 or 4 door) weighs 3,041 with DSG. I assume that's the 2 door weight because the picture above the specs on VW's site shows a 2 door. According to Audi's site, the A3 gasoline weighs about 3296, no spec is given for the A3 TDI.
I have a 99 Audi A4 that came with 288mm rotors stock. Like many A4 owners, I have switched to A8 312mm rotors by using an Audi TT caliper carrier and the stock A4 calipers (which look remarkably similar to those on our 2010 Jetta Sportwagen).
With the 312 mm rotor, the brakes work very well since they have more of a mechanical advantage (the pads are farther from the center of rotation = more braking torque), plus the larger rotors dissipate heat better.
Keep in mind that a larger rotor means more weight and a larger rotating mass, and that means slower acceleration. I personally wouldn't go any larger than 312mm unless I had a lot more horsepower to tame.
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