On a stock car, rotor heat conducts to the rotor hat, which then conducts into the knuckle and wheel. After a session, the wheels being a few hundred degrees is not unusual.

This is part of the reason why 2 piece rotors are used; it helps keep the heat in the rotor to dissipate away, rather than conducting out to the knuckle and wheel, which doesn't have as much surface area relative to the mass. That heat can also contribute to wheel bearing failure, and wheel fatigue, in extreme cases.

I'm surprised you warped the rotors with stock pads. Did you set the parking brake after coming off track, or hold the brake in pits/paddock for a long time after coming off?

The rotors are likely not warped.

What he's probably feeling is the effect of brake pad compound smeared all over the surface of the rotor.

When I melted my OEM pads (lazy, didn't take them off one day) the feeling afterwards was terrible.

Eventually the pad material scraped off and things were fine again.

Rotors don't warp. That's almost a myth.
Maybe solid rotor, but ventilated rotors (like all front rotors, and the twins rear) are almost impossible to warp. They will crack before warping.


The feeling of warp rotor is almost always pad material not evenly transfered on the rotors because of overheating, or appliying the brake when stopped, or a craked rotor.
Bad transfer layer can sometimes be corrected by bedding-in or "turning" the rotors.

In my limited experience (some 4 years doing HPDE and time attack, around 30 days total), I have never had a warped rotor, but I had cracked some and its as you say, they feel like warped (vibration on the pedal). Even with uneven/bad transfer layers on the rotors, it didnt really make much of a difference to feel (it did to braking distance on the other hand).

Almost a myth is correct. Pretty hard to warp a car rotor since it has to be heated up extensively and very quickly. Even the hardest track braking doesn't do it fast enough so as you said they crack instead.
We make pick up truck (and some car) rotors where I work and every couple of months we get a set of badly warped vented rotors sent back for warranty investigation. They are always the front and the dealer documents usually start with "customer was going down a large hill pulling a heavily loaded trailer and noticed a pulsing in the brakes right after". Conditions like that can warp them pretty badly.

I am amazed you got SIX days out of stock pads. If you were hard on them, they'd be smeared in a day. I run Carbotech XP10 pads and have no issues with my brakes at all.


The wheels get very, very hot, but are most definitely not deforming at the hub so much that the caps fall out, as someone else suggested. The tabs get soft when they are riding in a 200+ degree wheel.


One thing I did preemptively, based on experience with my WRX, is replace the stock lug nuts. I would get stripped nuts every time I hit the track with that car. Yes, I own a torque wrench. No, I did not cross thread them. They are of terrible quality.


My Primacys are working well and have several weekends on them. Coming to the end of that road, though...


Oil cooler goes on this week, as I would like to see temps stay well below the 270 max I am seeing now.


I really don't expect anything else to fail at this point. I just want 17x9 wheels and stickier rubber :thumbsup:

Subaru replaced the center caps free of charge.:w00t:

-Called dealership parts department, ~$30 for Subaru caps and $50 special order for the STi caps, this is more than I want to pay on plastic caps that pop out.
-First local dealership service advisor I talked to told me centercaps are not covered by warranty, I said “Oh, so it’s normal for these to fall off?” He backtracked a bit and then elaborated that “the warranty item is no longer present.”
-I emailed Subaru NA and they said to schedule an inspection of the matter at that dealership and provided an SR#. I let them know what date the inspection was scheduled.
-Dropped my car off at the dealership in the morning and picked it up at lunch, they asked for the SR#, this second service advisor was super friendly, and sent me on my way with two new centercaps and a receipt for $0.00
-Subaru NA gave me a follow up call an hour later and I let them know I was happy and told them “Thanks!”

Really liking Subaru at this point.

Just wanted to chime in on this. Yes, racing pads are a MUST. I have not run a lapping day on stock pads but I can say the four lapping days I've run with Winmax W5's has been incredible. I just did a full day covering approximately 180 miles at Pueblo Motorsports Park today. Between the pads, Castrol SRF React brake fluid and Potenza RE-71R tires, I can stand on the brakes all day long with zero fade. I'm pretty sure the heat has discolored my calipers already, but ironically my center caps are still snug as a bug in a rug (maybe I'm pushing my luck and should remove them).

On the subject of tires, a lot of people say the RE-71R is only good for a quick sprint or one good hot lap before they fall off and I don't know what they're talking about. I was lapping consistently all day, the only variation in time due to driver error. They started to fall off only when I wore the outer shoulder off because I don't have enough front camber yet. I'm on my second set only because I was moving cross country and didn't want to drive 2,000 miles on my first set which is still at ~4/32nds; I'll get another event or three out of them I suspect!

I broke a wheel stud this morning from said terrible lug nuts and am going to break another one tomorrow when I go to swap my pads. Any recommendations on a good set of lug nuts? I was considering getting ARP extended studs eventually, too. Friend of mine has broken his fair share from swapping wheels so many times at the track, too. I was 90% sure I didn't cross thread mine, either!

Oil cooler, yes. My temps are creeping just above 270 and that seems like danger zone territory to me; the temp has stayed consistent with zero power loss or warning signs, thankfully. I run Pennzoil Platinum Euro 5W30 in case anyone cares.

I'll gladly demonstrate for you if you come out to California!


Check out https://www.counterspacegarage.com/c...ugnuts-m12x125 They're made with SCM435, which is a chromoly alloy specifically designed for shafts, gears, and screws exposed to high stress high temp.

After an autocross competition day with 4 60 second runs my wheels were hot enough that I couldn't swap them right after my run group without waiting for them to cool off. This was on stock callipers and Winmax W3 pads.

New vs tracked center caps: :bellyroll:

https://youtu.be/U-4WL2PTzYQ