Last HPDE of the year - Cracked Rotor
10-12-2006, 08:38 AM
#1
Team Owner
Thread Starter
Last HPDE of the year - Cracked Rotor
I did my final HPDE and with some seat time with an instructor I cut down my brake usage by a huge amount.
I ran Wildwood J's and...Penzoil brake fluid...I bought it to flush the system since I had to replace a brake line and had a ton of air in the system. My neighbor who works for one of the OEM's said they did a lot of testing of various brake fluids and the Penzoil stuff was pretty decent and in most tests better than the Super blue. Ford's old race fluid was the best, their new stuff is junk since they changed the formula.
I bought ATE Super blue with me just in case but drove the entire day on the Penzoil stuff and never had a single problem.
I used the brakes much less and turned in a respectable time(for me) of 1:35 around Grattan. A Z06 with a race alignment was turning 1:34 so I felt pretty good about my setup since my car must be at least 200lbs or more heavier.
I used the brakes way less than I had in the past. I still ended up cracking a rotor.
I did cool down laps, used them way less and the track was pretty cold overall.
Napa rotor, only run on the J's, never on a street pad. My neighbor seems to think that one of the pistons got hung up and I had a pad dragging creating a hot spot that caused the crack. My calipers have a decent amount of abuse on them and I'm sure there like jello.
Next year, LG Brakes, seats, and a trailer.
I ran Wildwood J's and...Penzoil brake fluid...I bought it to flush the system since I had to replace a brake line and had a ton of air in the system. My neighbor who works for one of the OEM's said they did a lot of testing of various brake fluids and the Penzoil stuff was pretty decent and in most tests better than the Super blue. Ford's old race fluid was the best, their new stuff is junk since they changed the formula.
I bought ATE Super blue with me just in case but drove the entire day on the Penzoil stuff and never had a single problem.
I used the brakes much less and turned in a respectable time(for me) of 1:35 around Grattan. A Z06 with a race alignment was turning 1:34 so I felt pretty good about my setup since my car must be at least 200lbs or more heavier.
I used the brakes way less than I had in the past. I still ended up cracking a rotor.
I did cool down laps, used them way less and the track was pretty cold overall.
Napa rotor, only run on the J's, never on a street pad. My neighbor seems to think that one of the pistons got hung up and I had a pad dragging creating a hot spot that caused the crack. My calipers have a decent amount of abuse on them and I'm sure there like jello.
Next year, LG Brakes, seats, and a trailer.
10-12-2006, 09:19 AM
#2
Drifting
It's an indication that you are running quick and using the brakes hard. If you're fast and you drive a C5, you will crack rotors even if your calipers are in perfect condition. I crack 5 or 6 each season and pistons push back in bores by hand. 
10-12-2006, 10:52 AM
#4
Team Owner
Thread Starter
They had been run in 3 sessions 1 month before and 4 sessions that day.
Its strange that it only cracked on one side of the car and only only the outside. Thats what led us to believe the piston was hanging up.
I've cracked rotors before, in half, but after much more abuse than these took.
Its strange that it only cracked on one side of the car and only only the outside. Thats what led us to believe the piston was hanging up.
I've cracked rotors before, in half, but after much more abuse than these took.
10-12-2006, 12:34 PM
#5
Drifting
All the cracked rotors in my pile in the basement are cracked from the hat to the outside diameter, but only on the outside surface. This applies to both front and rear rotors.
10-13-2006, 12:29 AM
#6
Melting Slicks
My stock and NAPA rotors on my Z06 both cracked on the outside only. And the crack was from hub to lip.
As it was explained to me the outside cracks normally because it cools at a faster rate than the inside. Once you come off trakc and pit your car heat escapes from the rotors. Plus any breeze is hitting the outside face. So the outside cools much quicker. The rapid cooling causes the crack.
I've seen one guy put carboard covers against the front wheels when he comes off track and pits the car. Supposedly stops the outside face from cooling too fast. Not sure if it helps or not.
As it was explained to me the outside cracks normally because it cools at a faster rate than the inside. Once you come off trakc and pit your car heat escapes from the rotors. Plus any breeze is hitting the outside face. So the outside cools much quicker. The rapid cooling causes the crack.
I've seen one guy put carboard covers against the front wheels when he comes off track and pits the car. Supposedly stops the outside face from cooling too fast. Not sure if it helps or not.
