AddictedA4

vented rear would be nice. I will have stoptech's in a few months-- will the smaller a4 master cylinder be an issue? Thanks

Longwolf (Christian)

I do recall hearing that rear brakes on S4s fit A4s.

Liam in Montreal

direct swap

Steveo369

I just went through this issue. See my sub posts on a couple of braking threads.

The bottom line is that the piston diameter is close to the same, but the rebuild kits are different, so I'm not sure exactly how different they are. The OEM pads for the S4 are slightly different (different part number), but the backing plate is the same size. Some aftermarket pad manufacturers don't differentiate between rear pads for the A4 and the S4, others (and Audi) do.

The rotor diameter and width is different (A4 = 245x10mm, S4= 256x22) the width is obviously different due to the venting, which makes the caliper different to accomodate the wider rotor, and the carrier is larger to move the caliper outward. You need the S4 dust shields as well, as the rotor size will cause rubbing, even though it's only 11 mm larger in diameter.

Basically, if you can get your hands on a full S4 rear setup, it's a direct bolt on swap.

S4 rear brakes vs A4 rear brakes <-search terms.

Cris

<ul><li><a href="https://www.audiworld.com/tech/wheel1.shtml">https://www.audiworld.com/tech/wheel1.shtml</a></li></ul>

Steveo369

<ul><li><a href="https://forums.audiworld.com/a4/msgs/1957982.phtml">https://forums.audiworld.com/a4/msgs/1957982.phtml</a</li></ul>