Why don't all 4.2 wheels fit 2.7 with HP2s, caliper clearance only
12-21-2004, 11:01 AM
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Why don't all 4.2 wheels fit 2.7 with HP2s, caliper clearance only
Besides the fact that they may be too wide for the 2.7, shouldn't 4.2 wheels have clearance for the HP2 calipers too, or am I just missing something here?
12-21-2004, 12:10 PM
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The real reason...
Is that 4.2 wheels (e.g. Pie Plates) will rub on the HP2 calipers on SOME 2.7t equipped cars. This includes early A6 and S4 models. When I say early, I mean mostly MY2000.
As you may know the HP2 calipers came with 2 rotor offsets. The earlier units had less offset and subsequently the caliper sits further outbound. I can only assume that ALL 4.2 models had the later version of the HP2 caliper with the deeper rotor offset. Hence the wheels spec'd for that car have different brake clearance considerations. The problem can be mitigated with the use of hub spacers.
IIRC the specified offset for the 2.7t is ET45mm and for the 4.2 is ET35mm. I think the RS6 is ET30mm and the Allroad is ET25mm.
Please note the width and offset of a 4.2 wheel is not the limited factor for fitment on a 2.7t. On my early 2000 2.7t, I am running RS6 wheels; 18x8 ET30 with 255 tires and there is still room. In winter, I am running 4.2 Pie plates; 17x8 ET30 plus 3mm spaces on the front wheels to clear the HP2 calipers. There is no fitment issues in regards to width of the wheel and the suspension components or fender.
As you may know the HP2 calipers came with 2 rotor offsets. The earlier units had less offset and subsequently the caliper sits further outbound. I can only assume that ALL 4.2 models had the later version of the HP2 caliper with the deeper rotor offset. Hence the wheels spec'd for that car have different brake clearance considerations. The problem can be mitigated with the use of hub spacers.
IIRC the specified offset for the 2.7t is ET45mm and for the 4.2 is ET35mm. I think the RS6 is ET30mm and the Allroad is ET25mm.
Please note the width and offset of a 4.2 wheel is not the limited factor for fitment on a 2.7t. On my early 2000 2.7t, I am running RS6 wheels; 18x8 ET30 with 255 tires and there is still room. In winter, I am running 4.2 Pie plates; 17x8 ET30 plus 3mm spaces on the front wheels to clear the HP2 calipers. There is no fitment issues in regards to width of the wheel and the suspension components or fender.
12-21-2004, 12:18 PM
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Wow, thanks for the super detailed response!
That answers about all my questions. I have a 2001 2.7 so hopefully I'll have the newer offset calipers. Interestingly, I am also looking to get some pie plates, but I was under the impression they were ET35...
12-21-2004, 12:30 PM
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Exactly right. My 2000 2.7t has the shorter 16.7 mm hat offset.
From the ecstuning's site about brake rotors:
"There are two different front braking systems for the A6 2.7T's. Audi calls them by code letters (PR-T7S & PR-T7Z). Since most Audi owners don't know which front brake system they have, we will give you information on the differences. The rotors themselves are the same size, the only difference is offset of the rotor hats. One of them has a 22.7mm offset & the other has a 16.7mm offset. You must remove the wheel in order to check to see which one you have but it's fairly simple after that. Simpley lay a measuring device on top of the hat to the front part of the rotor ring (see pictures), then order the correct offset per the description lines. They do however take the same brake pads."
"There are two different front braking systems for the A6 2.7T's. Audi calls them by code letters (PR-T7S & PR-T7Z). Since most Audi owners don't know which front brake system they have, we will give you information on the differences. The rotors themselves are the same size, the only difference is offset of the rotor hats. One of them has a 22.7mm offset & the other has a 16.7mm offset. You must remove the wheel in order to check to see which one you have but it's fairly simple after that. Simpley lay a measuring device on top of the hat to the front part of the rotor ring (see pictures), then order the correct offset per the description lines. They do however take the same brake pads."
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12-21-2004, 01:43 PM
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The A.6 4.2 hd HP2 calipers
IIRC, the 4.2's stayed with the HP2's through the entire production. Where as the 2.7t went to something else around MY2003. I believe this applied to Allroads too.