Short of pulling the rotor off and measuring it, is there any way to tell what size the rear brake rotors are on a B6? I'm due for rotors and pads at all four corners, and they either come in 245mm or 255mm. I pulled the wheel off to look for some sort of stamp/marking, but found only some cryptic code that doesn't google well. I laid a ruler across the top of the hub, and it "looked" 245mm'ish, but that's not accurate enough for a 10mm difference.

 

ECS tuning.com get the rear rotors for the car and your all set they are OEM

 

Yes, OEM rotors, that happened to come in either 245mm, or 255mm diameters, and did not come marked as such.

 

Just measure the back of the rotor like you did, if its close to 245mm thats what it is.
The 255mm is usually newer model B6's that are probably ultrasport models.

 

I actually measured across the front, but was sure to keep my head perpendicular to the plane of measurement when checking the edges. Mine is a "sport" model, is that different than the ultrasport? I ran the option codes from the sticker in the trunk, rear brakes are designated 1KD = disc brakes rear, which doesn't seem to be related to size, and I cant find anything about the string of crap stamped into the rotor itself.

 

i had the same problem... some people told me newer models had the 255mm older ones had the 245m etc..i talked to audi and they said there is no rhyme or reason to it.... i dont know how u could manufacture cars like that but its the dealership... who knows?


i just took my wheel off and made a cardboard cut out

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l l

shaped like that it the size of the rotor then measured that... mine were 245mm

 

Not wanting to pull the wheel off again, I measured the circumference of the center hub using a piece of magnet wire (465mm), then measured the edge of rotor to center hub(50mm). So, take the circumference, divide by pi, multiply the edge to center by 2, and add them all up.

(465/3.14)+(50*2) = 248mm

Which is close enough to 245mm for me, a 3mm difference is easy to account for given the measuring methods.