ModifiedA4

this <a href="http://translate.google.com/translate?u=http%3A%2F%2Fwww.der-audi.de%2Fwsc75273706%2F37499%2F37526.html&langpai r=de%7Cen&hl=en&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools">site</a> seems to indicate s4 rear brakes(256mm) are possible with only the rotors and carriers. i cant find anymore information on this, so im tending to lean towards the common knowledge here that it cant be done with out the s4 calipers too. i cant find any direct evidence here either that it cant be done, just anecdotal.

qfrog Ti20

the calipers must be changed too iirc.

however you can upgrade to 255mm rears with just rotors and carriers if you search for some of my old postings about that topic. None of my parts are from the S4 tho.

Silver Streakin'

I'm thinking about doing the B6 A4 rears before the track/race season starts in April. my OEM rear rotors are close to being done.

carrier and rotors needed only.

Rear brakes to B6 3.0 carriers (8E0-615-425-A) and A6 255mm x 10mm solid rotors (4B0-615-601-B).

ModifiedA4

i was just looking into it...and found that web page.

Silver Streakin'

I found that with weak spring rates up front (H&amp;R A4 streets) -- I had too much front brakes (StopTech with Pagid Oranges and HP+ in the stock rears) since a lot of the weight would tranfer to the front under heavy braking, namely at the end of long straights. The car would dance a bit because the fronts would lose grip even with the Azenis Sport tires. I learned to be easier on the brakes, but I wouldn't mind a little more rear brakes. It almost feels as if I do - now that I have Stasis Tracksports 600/750 = less transfer of weight to the front and keeps the rear down.

After watching some of my out-of-car vids, I can see it happening. People watching would also mention the huge nose dives and rear lift under heavy braking.

JAFO

it says that you need the calipers too in the parts list.

ModifiedA4

since the a4 shares the same rear suspension component the only variable between the two rear brake setups is the caliper.

if the a4 and s4 caliper had the same offset from the carrier to centerline, then that would mean the s4 carrier alone accounts for the rotor thickness difference. which would mean the simplifed s4 rear is possible.

it seems unlikely this is true, but its all still anecdotal.

it also seems that since the 245x12 brakes on the b6 a4 use the same carrier as the b5 a4 and the same caliper as the 255x12 also on the b6 a4...that the calipers on the b5 and b6 a4 are dimensionally similar.

because of this a pure rear upgrade to b6 a4 255x12 brakes seems like a direct bolt-on:

8e0 615 601 D
8E0 615 425 A

ModifiedA4

might as well buy rear rotors and carriers and do whatever is possible then too.

RKA

cheaper rotors, reuse existing calipers, and so far, nobody has demonstrated a need for vented rear rotors...so in absence of that, I'd say it's safe to assume you don't need them.

Ritz

The fronts do the vast majority of the "heavy lifting". If you make the rears a LOT more grippy than stock, it can make the car unstable during panic braking, even with ABS.

Cheers,