NightOwl

I’m in the thinking box regarding upsizing the brakes in my A8 D3. Mostly because it has the smallest discs mounted on the D3, and then driving with 19 inch summer wheels (18 inch winter wheels) makes the small discs more apparent. The discs are now 321x30mm in the front and 280x20mm in the back. There are several options to choose from, and I’ve been thinking about 360x34mm in the front and 335x20mm in the rear.

Anyone having any experience in such a job?

Will there be any conflicts with the onboard computer regarding changing disc size?

The wheel bearing housing is the same on all the models as far as I know, so there shouldn’t be any worries there.

The carrier needs to fit the size of the disc size, so they need to be replaced front and rear.

The calipers on my car are one piston type, and for the 360x30 front discs, it needs to be a two piston type, so they need to be replaced too. In the rear I can reuse the old calipers.

I’m aware of the EPB in the rear, but as the old and the new discs have the same thickness, I’ve been hoping it could be as simple as to slide off and on the caliper without any other changes to the caliper. As I don't have VAG-COM yet.

Anyone who can follow my thoughts and can confirm that all this should be a simple bolt on job? Or any other thoughts, suggestions or ideas?

mishar

Welcome to the board!

I believe you are in Europe but it would be nice if you fill your profile. It helps people to help you.

I've replaced my 360/310 rotors with S8 385/335 rotors. It was bolt on job, but I've replaced calipers too.

By replacing those small brakes you will get much better braking which is, in my opinion, more important than looks.

I would not suggest mixing rotor sizes from different models. So with 360 mm fronts rears should be 310 mm. It is also much easier to find them. If you go with larger rear brakes you can get too much braking at the rear. That would put your ABS in overtime mode and possibly make hard braking unstable and unsafe.

Used calipers usually come with carriers. I would suggest buying rear calipers too, probably without motors. That can be cheaper than buying new rear carriers. You also need larger dust shields and new brake pads.

You have to check size of the master cylinder. Since your front calipers are single piston and 360 mm are dual piston you need more flow but less pressure. If you keep your master cylinder you will get low brake pedal.

You definitely need VCDS in order to program new brakes.

NightOwl

Thanks! Living in Norway, also added in it my profile.

The front calipers needs to be replaced, but as far as I know, the rear calipers has the same part number regardless of the disk size.

That's very true!

You probably right and I was a bit worried about that. The reason why I suggested 360mm in the front, was that I didn't think the 385mm would fit under my 18 inch winter wheels. But just found out that the D3 W12 comes with 385mm disks and 18 inch rims as an option (19 inch as standard size). So this mean that it could be just as good idea to go for 385mm in the front and 335mm in the rear.

I will look into that as new carriers are a bit pricy. The dust shield in the back seems to be the same for all disk sizes, but for the front I guess its better to replace it with the right size.

Will look into this too.

Have some friends with VCDS, but I guess its good to have one "in house".

Thanks for your insight!

mishar

Even better.

I had 18" aftermarket wheels and they didn't fit on 385 mm brakes. That W12.S8 spare obviously fits, but you should check those you have.


Actually it is just the opposite. You can keep front shields (not perfect) but rears won't fit at all.

NightOwl

Mine 18" are also aftermarket, so its hard to tell, and potentially expensive to try and fail...


Ah, you are right, 280mm and 310mm rear disks share the same dust shield, but they won't fit the 335mm.

I've checked the tandem brake master cylinder, and it seems like its the same on all models. I guess the bigger single piston equals out somewhat the smaller dual pistons?

NightOwl

Another think that has come to my attention, is that the ABS unit has different part number for 8 cylinders including diesel engines, 10 cylinders and 12 cylinders. Means 3 different ABS units...although the drawings looks exactly the same. Not sure what to make out of it.

Might add that mine is a 3.0 TDI.

Mister Bally

Different part number for ESC/ESP (Electronic Stability Control/Protection) equipped ABS units. If your vehicle does not have the extra valves in the ABS unit, Yaw sensor and Steering Angle sensor, the ECU will look for them and when it does not "see" them, a fault will be generated. Always replace with the proper part number. Ask a dealer to confirm.

mishar

Add that to your profile too.

MP4.2+6.0

in front. Did when I got some 20's refinished. The standard five spoke U.S. base wheel that is, which is the same as the black painted spare found with the D3's that came w/ 20's. It is very close, but it fits in all respects. Both the barrel clearance in general and caliper clearance bar the spokes are critical.

MP4.2+6.0

To your original post, yes the 360 and 385mm factory set up are two piston calipers (Ate)--floating, meaning the pistons are both on one side. I think the only actual difference is the caliper carrier. In non-OE pads like EBC, they use the same pad part # for either one.

Also, you can find donors from the C6 S6 that had similar larger brakes.

FWIW too, I don't really think the rears should be 335mm only if the fronts go to 385mm. In practice, the ABS can sort that out in true emergency stops for starters. But at a more basic level, as pointed out the caliper is really the same; it's the carrier that varies. Other than the electric parking brake that same bail caliper has been typical Audi rear brake parts bin stuff for many years. The pad pressure being put on the rotor is the same given the size delta is in the carrier, though the effective lever arm length varies. The 335's also have more swept area to them and thus greater resistance to heat and perhaps somewhat longer rotor life. While it is a different specific rotor (semi floating type), the C5 RS6's used 335's in the back, and in that era were not up to 385mm in front, whether the better Euro spec set up, or the cheapened U.S. one. You can find 330's in the back of Q5s as another example with everything from 345mm front stock on a Hybrid, TDI or 3.0T, all the way up to 380mm on the SQ5--which themselves come right out of the D4 smaller motor set up parts bin. In other words, even on the same platform, Audi varies the fronts a fair amount compared to the rears.

Finally for what its worth, if I were doing D3 brakes in front again, and I did not already have 385's (like I do with a W12), I would actually probably go to the 365 mm Audi OE Brembos with the semi floating rotors. This assumes the target is true higher performance though, and not simply big brake "looks." Pricier on both rotors and calipers though. The donor would be a B7 era RS4 with steel brakes (not ceramic), though the calipers can come from RS5's, RS4's or (steel brake) R8's. Not that hard to find the calipers on various country EBay's from my prior searches if you take your time to find a good buy and good condition. You want the "older" rotor set up (which I typically buy as new for rotors anyway) to get the right hub center for the D3, rather than the B8 RS4, RS5, etc. ones which will have the current hub design like the D4 does. I am running those brakes in front on my Q5, and the rotors came from an RS5 since the Q5 is the newer hub center size too. I pulled off the stock 345mm standard steel front rotors and some pretty generic current two piston Audi mass production calipers. The RS4/5/R8 calipers are 6 piston Brembo, and with the semi floating rotors overall (even with some sizing up diameter wise) can pull some weight out or at least not have it go up as much. There is a 390 mm set up like this that was used on the C6 RS6 that also crosses over, but it is basically not obtainable from the U.S. and hardly ever found on Euro EBay's. Both use very wide Brembo typical designs given the opposed piston non floating calipers, so wheel fit is important, or spacers in lieu. You also have to deal with the pad sensors (external on the RS ones, but only on one side), but that can be adapted and kept on both fronts like the D3.