Found a crack in the right rear rotor. These are the JHM two piece rotors but it’s probably not their fault. They are 330x22 so pretty small and I was running them on Pagid RS19 pads full time. Does anyone know if the RS7 355mm rear rotors will just drop onto a B8 if I order them from the dealer? Or is it a huge hassle?
how big of a crack are we talking, do u have any pics?
I’m curious to see the cracks too. Assuming it went through the surface (and into the vanes)? Was it on the outside or on the inside (closer to the hub)?
I might need to go with these: http://www.ecstuning.com/Audi-B8_RS5--4.2L/Braking/Rotors/ES2642807/
Never mind was in title lol…
I wonder how much the fact that they aren’t floating caused this.
did you contact JHM to see if they would warranty it for you? it seems you are the first to have cracked one of their rotors, it may have been a defective blank.
In theory you could crack any rotor with the right amount of abuse. I doubt JHM would warranty these, and I believe they have a disclaimer about road course use. My guess is these rotors aren’t great for track abuse. If you get 2 piece, you want a floating setup to allow the outer ring to expand and contract as it goes through the extreme heat cycles of stopping a 4000lb car at stg 2 power levels. My stoptechs in the front make all kinds of noise as I pull into the paddock after a session.
I think west is just confirming what we might have guessed. I will probably see something similar if I track them a lot. He is also running a r-comp tire, which probably pushes the brakes harder than most.
I’m not aware of anyone else who makes a 2-piece floating rear rotor for the B8 S4. I know boro was looking around for a while.
yea closest to a 2 piece floating is the ecs ones. http://www.ecstuning.com/Audi-B8_S4-Quattro-3.0T/Braking/Rotors/ES2681143/
Not sure exactly what “semi-floating” means, but I wouldn’t run their setup based on what this RS5 guy saw after 4 sessions:
http://audirevolution.net/forum/index.php?topic=2995.0
http://i14.photobucket.com/albums/a348/vette_ruminator/IMG_2736.jpg
im sure also if you contact griodisc they will make a set.
west you can go s7 rear ceramics 
the rs5 guys bolt them on
http://i1257.photobucket.com/albums/ii506/CuppaChoc/IMG_20130203_170246_zpsafa08013.jpg
http://www.a5oc.com/forums/sale-group-buys/26655-fs-audi-s5-rs5.html
I would think that using r-comps would lessen the overall load on the brakes since you have a higher adhesion/traction limit (which also results in not having to slow down nearly as much).
They will not make a set.
I have already tried 
Apikol makes rotors. Though I’m not certain if they do rears.
FWIW, ECS semi floating means the rotor can expand outward (radially), but not laterally. That is, the rotors aren’t floating on both the x and y axis. They are only floating on the y axis. More specifically, the rotor ring is slotted for the hardware to bolt into (so the ring can expand radially).
10 real track days on rear rotors, on RS19s seems short. Did OEM last longer than this?
For fronts, I can see 10 hard track days killing a set if you are running crazy pads. But rear! Wow! you’re not driving with stability control on, are you?
I am not sure they would consider warranting a rotor that was used at 10+ track days and a year or two of driving (not sure how long he had them)
I would also remind everyone that another member’s Brembo rotors were cracking after 2 days at the track on his RS5. Track is abuse, plain and simple.
Frankly I think 10 track days is pretty good considering they say right on their web page that these aren’t for road-course racing.
That’s a good point. But it could work the other way: now you are entering corners faster because you didn’t need to slow down as much in the previous corner, and bleeding off 10 mph from a relatively higher speed will transmit more heat energy to the brake rotors, since KE = 1/2 mv^2. So I guess the validity of my claim should be considered under the assumption that the car is driven the same way (for the sake of debate).
Even then I wonder if my guess is true. Because with the added grip you slow down faster and are thus on the brakes for less time to achieve the same delta speed. On the other hand, the instantaneous force achievable from the brakes will be greater with the additional tire grip. But impact on the brake system should be measured in terms of energy transfer rather than instantaneous force applied.
So my guess is r-comp tires do less wear/tear on brake system/fluid because you stay on them for less time.
RS7 rear rotors will not just drop in, it will likely need a bracket and possibly a new hat.
According to ETKA it is a 356mm x 22mm. So the thickness is the same as the B8 stock caliper so with a bracket and correct hat this is a possibility.
If there is some interest on a rear BBK like this for the B8, we can look into getting it made.
Thanks Jake. Sorry I didn’t email you first. I think the RS7 conversion would make sense if the pad shape was larger and the caliper was better. Otherwise, dropping in RS5 rear rotors is probably more than enough.
The entire feature of this rotor is that it’s light. I think you have to assume it’s an annual wear item at 11 pounds. Gotta pay to play. I’ll spend the $1050 and go up to the heavier RS5 rotors, which should last 2+ years.
The fronts at 380mm x 32mm last 2 years and eat through 3 sets of RS-29.
No stability program. Tires were Pilot Super Sport for all 10 track days. The Pilot Sport Cups are new and I haven’t had a proper full track day on them. Just a little test session.
its the s7 rotors, someone did it on their s5, so i assume its the same for the s4. they just changed the lines, brackets, calipers, rotors and said it was all bolt on.
i think you need the rs4 rotors for the rear, if im not mistaken the rs5 ones you need a spacer unless you change the hubs also.
Thanks for the tip infinkc. I will in fact need the RS5 hub and new wheel bearings, as the old ones will get wrecked pulling the hub off. Man this job is getting expensive.