A4 vs S4 Caliper differences?

[vwnobby]

I have a set of A4 calipers on my bench and a set of S4 calipers on the car. I wanted to rebuild the A4 ones since the powder coating on the S4 calipers is starting to flake off.
I see that, according to ECS, Europaparts, etc.) that they are different part numbers, but I can't tell the difference.
Any know specifically what is different between the calipers?

[Charles.waite]

I assume you mean fronts? The caliper itself is the same, the only difference is the carrier is longer on the S4s for the larger rotors. The rears are completely difference between a4 and s4.

[aluthman]

I assume you mean fronts? The caliper itself is the same, the only difference is the carrier is longer on the S4s for the larger rotors. The rears are completely difference between a4 and s4.

Pretty sure this applies to the rears also. The part number for the remanufactured S4 calipers I bought was the same as the ones for the A4.

[vwnobby]

I assume you mean fronts? The caliper itself is the same, the only difference is the carrier is longer on the S4s for the larger rotors. The rears are completely difference between a4 and s4.

Yes, I apologize, I meant the fronts.
I just wanted to make sure that there were no differences, such as piston size, volume, etc.

[Charles.waite]

Pretty sure this applies to the rears also. The part number for the remanufactured S4 calipers I bought was the same as the ones for the A4.

The rear calipers are much much bigger. The s4 rear rotors are vented and 2x the thickness.

[Axis]

Yes, I apologize, I meant the fronts.
I just wanted to make sure that there were no differences, such as piston size, volume, etc.

The part number is different because they're a bit different.

You might have to grind 2-3mm off the top/bottom of the A4 caliper when paired with S4 carriers/S4 rotors.

[vwnobby]

The part number is different because they're a bit different.

You might have to grind 2-3mm off the top/bottom of the A4 caliper when paired with S4 carriers/S4 rotors.

Thanks! That's what I was looking for. So long as that is the only difference, then I should be good to go.

[Axis]

Thanks! That's what I was looking for. So long as that is the only difference, then I should be good to go.

If I'm not mistaking, late 07-08 A4 wont need the grinding.

[Chris@EPL]

I have a 2005.5 A4 and added the OEM S4 carriers and had no grinding and everything has been perfect for 200k miles. I also just the stock splash shields and never have an issue with the brakes getting wet from large puddles.

[vwnobby]

I have a 2005.5 A4 and added the OEM S4 carriers and had no grinding and everything has been perfect for 200k miles. I also just the stock splash shields and never have an issue with the brakes getting wet from large puddles.

Excellent! Good to know. If anything I can put my old A4 calipers on in the mean time and take my time refinishing the S4 calipers.

[Axis]

I have a 2005.5 A4 and added the OEM S4 carriers and had no grinding and everything has been perfect for 200k miles. I also just the stock splash shields and never have an issue with the brakes getting wet from large puddles.

I have a 2005.5 and had to grind, McSuly also had to grind on his ex 2005.5. Starting to wonder if its the carrier that causes that, but B6 and B7 S4 carrier share the same part number.

[Chris@EPL]

OEM carriers? And I would have to check on what part number I used, not sure if it is a B6 or B7.

[Axis]

B6 S4 Carrier : 1K0 615 125 B
B7 S4 Carrier : 1K0 615 125 B (Early B7)
B7 S4 Carrier : 8E0 615 125 C (Late B7)

B7 A4 Caliper : 4F0 615 123 | 4F0 615 124
B6 S4 Caliper : 8E0 615 123 B | 8E0 615 124 B
B7 S4 Caliper : 8E0 615 123 B | 8E0 615 124 B (Early B7)
B7 S4 Caliper : 8E0 615 123 C | 8E0 615 124 C (Late B7)

Confirmed, there's two different S4 carriers, pretty sure the late B7 S4 carrier is the one that doesnt require grinding

[kingDL]

hmm didnt the grinding issue only appear for those that bought aftermarket carriers?

[Charles.waite]

hmm didnt the grinding issue only appear for those that bought aftermarket carriers?

I think this was the issue.

[Axis]

I ran oem carriers and still had to grind.

[jgood2709]

Thought I'd bump an old thread and shed some light on this topic. Was upgrading the brakes on my B6 and made some discoveries.

I pulled the front brakes off of a B7 in the local parts yard with intentions of getting some S4 carriers and running 345mm rotors. I bought some S4 carriers from a member on here, and in some kind of confusion he sent me one B6 S4 caliper as well.

I installed the B7 A4 calipers since they were a matching pair. I ended up getting the clearance issue that a lot people have reported where the rotor rubs on the inside of the caliper. Wasn't enthused! Did some forum research and couldn't find a solid answer explaining why.

Decided to find a matching caliper for my B6 S4 caliper. It's difficult to do this by part number, but I noticed that some of the calipers on eBay that were listed as B7 A4 matched my B6 S4 caliper upon visual inspection. The matching caliper I got on eBay was listed as a B7 A4 Cabriolet caliper.

So it does turn out that there were two different styles of caliper for the B7 A4. Some will work with the 345mm rotor upgrade, and some have the clearance issue.

Left: Bad. Right: Good.
IMG_2992.jpg

IMG_2993.jpg

Not enough clearance with the left caliper.
IMG_2875.jpg

Adequate clearance with the right caliper.
IMG_2995.jpg

Best tell-tale visual difference is the extra bar going across the U-shaped gap on the outside of the caliper.

I know I'm super late to the party but hopefully this helps someone.

[Jayz691]

Is the bad one, the one listed for cabrio? Cuz seems lots of Cabrio stuff is slightly different. And I believe brakes is one of them.

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[Van Black]

I have the same rubbing issue, but when I bought the discs I told the rep to bring 345mm discs and instead got 347mm.
I noticed a lot later so that was that. I'll double check and measure them, but also have to grind the calippers now since those
marks are stress concentrators. The car's an A4 saloon and S4 carriers.

[wayneair]

Ok, since this thread has been resurrected, what’s the difference in B7 A4 and S4 rear calipers? The part # is the same except for the last letter. I was told the last letter only signifies the revision, and if the 9 previous digits are the same, it works...

[Charles.waite]

That’s definitely an accurate rule of thumb but it’s not a hard and fast rule.

Brake calipers are one of those areas where it doesn’t really apply.

Rear s4 calipers differ in the carrier being taller (300mm vs 288mm) but the main difference is that the caliper itself is much longer to accommodate the vented rear s4 rotor. The A4 rotor is solid and only 12mm thick. The s4 rotor is vented and is 22mm thick. The A4 caliper won’t even come close to fitting over the s4 rotor with pads installed.

[Dangerb]

FWIW: This photo also illustrates the caliper clearance issues you may encounter on certain wheels depending on what calipers you have installed.

calipers.jpg

Take the Alzor wheels model 881 from ECS for example, part ES#2678551. For the B7 A4 fitment they suggest you need 15mm spacers to clear the caliper, whereas you only need a 3mm spacer to clear the brake clip on B7 S4 calipers.

There's quite a bit more material on the outer edges of the calipers to the left (which are the same ones i currently have installed on my B6 A4 that have narrowed my possible wheel options )