Do B5 S4 rear brakes bolt onto B5 A4?

I guess what I should have asked first off is; if this is worth doing or I should just do the A8 300mm upgrade?

My pads fell apart- just like the front. YAY for PO's deadly cheap pads! I was lazy/no time, so my RR rotor was metal on metal for a few days before I could throw in some used spare pads I had.

So I need rotors & pads at minimum. I already have the S4 calipers/carriers, I just need to clean them up & reseal them. I had been waiting to do the 300mm rear swap to match because I have the ST40 fronts (which I think are overkill for me already).

But now I'm thinking it's overkill to go that big rear?? It's an avant but 1/2 the time it's empty. The othr 1/2 I've got scuba gear for 2 or other heavy stuff so larger than stock seems like a good idea(also to match the front!). S4 brakes would be easier/cheaper$ and also I could get it done sooner than the A8 brakes.

But if the S4 brake isn't even worth the gain, what's the point? I mean it's only a 246mm to 256mm difference iirc- but vented rotors help with fade tho right?

Please help! Opinions, speculation or btdt, etc, etc,

Those seal kits are a lot! I thought it was for both side but only one. Beats rebuilt calipers but then you get an entire caliper for $150.

Ok, ya that's along the lines of what I'm thinking. I guess any gain is good in braking and I already have the calipers/carriers, but need rotors/pads either way so if it's a fairly straight forward bolt on then it's worth it to m. 300mm would be good but I just want to get this done asap and not deal with making adapters, etc. I know I could buy them but I'm too cheap (& could make them for nothing), timing is bad though.

The S4 rotors from ECS are only about 5 bucks different than the A4(both Meyle) so not bad, and the pads are about the same cost A4-S4. I'm not sure on EBC Greens or yellow stuff or the Hawk HPS. I read a lot of A+ reviews about the HPS.

Are you using stock fronts on your A6 or? For some dumb reason I thought I could get away with being a slacker fixing my rear brakes becasue the fronts are stoptechs but no that doesn't seem to be so lol. Seems a lot worse than another stock A4 I drove for a few weeks that had metal to metal rear rotors/pads.

From what I've found The seal kit is about $42 from ECS and about that most places I've seen. Not horrible but seems like you'd find it cheaper like $15/per side. I thought I read a while ago when I was repairing a friends brakes on his S4 that there's a GM caliper that the boot/seal works on but heck if I can find it now...