SunnydayDILYSI

I recently finished my fourth HPDE weekend and noticed a lot of 1/4 to 1/8 inch heat checks on the surface of my Napa rotors (rotors were new prior to my first HPDE in May). I have been running on Hawk HP+ pads and just finished off my first set in the front (backs still look good). Based on your experience, do you expect heat checked rotors to make it through another weekend without a real crack, or is it time to change?

Thanks,
Chris

rithsleeper

Its so easy to change a rotor, i just wait till they crack and have new ones on hand... they look like crap once you punish them, the heat marks are normal just like surface cracks. Only prob is when new one goes on pad has to bed before you go into super hard braking.

crease-guard

Make sure you check the inside surface of the rotors as well. I had a set of fronts I replaced earlier in the year and only had those "heat" cracks on the outside. There were a lot of them so I knew they would start linking together. When I got the rotor off, there were 3 cracks on the back of left and 2 on the right that were edge to edge. I was on borrowed time and got damn lucky they didn't shatter.

Lesson learned, I check the inside surface first then the outside.

Jay

rithsleeper

Mine have never "shattered" i doubt on a hpde they would be capable of such a catostrophic failure, i immediately feel when the crack, it makes braking very rough with lots of vibration, just come in and change them to my street set.

another idea i had is pre bed your extra set. Little extra work beforehand to avoid bedding the new pair. Good advice on checking inside, never thought about that.

CHJ In Virginia

Heat checking is par for the course on track rotors. I examine mine after they cool down from each session. If a crack is big enough to catch a finger nail in and it extends to the outer circumference of the rotor - the rotor is gone. I recently switched to the DBA two piece rotors and life is greatly extended over the Chinese crap being sold today.

Last C5

They're good till they really crack. You'll feel the vibration on the first turn if you didn't hear the "tink" while you were setting in the pits. Just change the rotor then and give yourself a few laps to rebed the pads.

yakisoba

Confirm that run til you crack is what I do. A big crack is really noticeable. The only other trick I do is to make sure I use teh brakes VERY little during cooldown and move the car a bit so that the pads don't sit on the rotors too long once I park it. That also lets me check for cracks. My rotors rarely break on track. Almost always in the pits, so check them 20 or so minutes before you go out so you have time to change one before the session.

Aardwolf

It sounds like they have some life in them but it's tough without a picture. If they were mine and I was going to do a two day event I would probably change them. I do not prefer to change them at the track but that's just tired old me. By the way they sound I would trust them for a single day event. Save them for spares if you do change early.

JeremyGSU

Did it look anything like this?



I used mine for several more track events if I recall and they never fully cracked.

rustyguns

That is what mine look like before they crack change when they crack

gmccreary

When they look like this

taken19

That one appears to have a crack to the edge at the 12 o'clock position. Is that true or just an illusion in the pic due to lighting?

Scooter70

x5 on running them until they crack. When they do, you'll know it. These Brakemotive rotors don't seem to heat check much before they crack due to thermal expansion.

SunnydayDILYSI

My rotors don't look nearly as bad as Jeremy GSU's. The cracks are much shorter and are just towards the middle of the burn path. I'm going to follow in the footsteps of many of the other posters and give them another weekend, while also bringing a spare set along just in case.

Sounds like I need to start practicing quick rotor changes for when they do go "tink". I've only done it once so far, the caliper bolts took me forever to break loose, but I think I have the technique down now (very large breaker bar, my impact wrench wasn't getting the job done).

Aardwolf

Turning the wheel makes access better!

Gary2KC5

when you can put a credit card through the crack then replace the fronts ASAP, and if it's on the rear, start thinking about replacing them.

Zenak

Did you ever ready the sticky in this forum for all these questions here:
http://forums.corvetteforum.com/auto...e-learned.html

surface cracks are fine. CHECK FOR OUTER CRACKS. If you see any cracks from the outer edge of the rotor, those are the kind that split. Also heres something you need to do, after the car is in the paddock, and sitting for about 5 minutes, ROLL the car about 6-8" and then stop. THe rotor will cool faster in all areas EXCEPT where the calipers shield the rotor from shedding heat. the asymmetrical cooling causes he rotors to buckle. new rotors not so much, but as they age this get more and more pronounced by heat cycles. Rolling the car after paddock EVERY time you come in is a great way to extend rotor life.

brake cooling ducts are also a major factor, as are all the brake cooling methods in that link

MarkDFW

My 2 cents:

If you aren't going with 2 piece rotors, try Centric High Carbon Plain 125 Series Rotor. Seem to last quite a bit longer than the cheaper Napa rotors and not that much more money. I've run four HPDE on them and run with advanced group and haven't cracked them yet.

sothpaw2

This is good advice. In terms of cost/convenience, you should change the rotor just before it cracks all the way to the edge and is thus very, very, very apparent in the pedal when you try to brake.
What you are looking for is long cracks near the outer perimeter of the rotor that will soon threaten to go to the edge. To cause a crack to the edge, I find these also will need to be large openings where you can hang a fingernail. So look for large opening cracks that are getting near the edge. I would say that if such a crack tip is just 1/8"-3/16" from the edge, this should be replaced now.

Note: For front rotors, you want to be more conservative as if you put a new one on there, you lose 1/2 session with burnishing the pad to the new rotor. I had this happen once...the car won't stop (severe brake fade!!!) for 10-12 minutes; then suddenly all is well. So for fronts, it's best if the rotor looks good for 4 sessions (full day) so you can change and bed them in after the paid sessions are over.

A final hint in addition to the above on rotor life: when you do your "move" of the car in the paddock to move the caliper's position on the rotor, DON'T LEAVE THE HOT CALIPER SITTING ON TOP OF A SUB-CRITICAL CRACK. I always see 1 or 2 cracks on a rotor that are far worse than anywhere else...these areas should not have hot caliper sitting on them.

SunnydayDILYSI

I got into the DE CoTA event, so decided not to risk any down time and swapped out the rotors. After getting the old ones off, it does look like they have a lot of life remaining. Only 0.5mm of wear on the fronts and 0.1mm on the backs after going through a set of HP+ pads on the front and about 25% of the HP+ on the rear. The surface cracks on the front just started to make me a bit nervous, but I needed a good set of backup rotors anyway.

Zenak - Yes, your sticky rocks! I've read through it a couple times and still reference it regularly (that's where I got the idea for the Napa rotors). I also took your guidance on the AR headers, NT05 Tires, CCA pedals, Bilstein shocks, new belts, SS brake lines, speed bleeders, DRM brake ducts, DRM enlarged radiator with integrated oil cooler, and just ordered my upgrade to Carbotech pads. Hope to upgrade sway bars, bushings, seats and harnesses in the spring. Thank you for putting the sticky together, and sorry to hear about #99. I hope you are back up and running.