Cracked yet another rear rotor

[nsxtasy]

Here's another vote for "why the heck are you having problems with the REAR rotors?".

I have over 12,500 actual track miles on my NSX. I'm on my 14th set of front rotors; they usually need replacement because they eventually crack, even with the cooling ducts I have in front. I'm on my 2nd set of rear rotors; I replaced the first set because of thickness, and have never experienced any cracking or other heat-related problems with the rear brakes, even though I don't have cooling ducts to the rear. I get about twice as many track miles to a set of rear pads as front pads.

As for "taking abuse", I consider brake rotors, like brake pads and tires, to be "consumable" items which will need to be replaced frequently when the car is tracked. I have no complaints about the ability of my NSX to stand up to track abuse; it has done remarkably well with virtually no track-related problems.

 

[dquarasr2]

Right, you could always go with a big brake kit though that brings upon it's own series of headaches (cost, fitment, wheel fitment, rubbing, etc). But you won't worry about your brakes ever again. And for some, that alone is worth the price of admission.

I'd seriously consider the NA2 Racing Brake option, 2 piece front and rear, maketed by ScienceofSpeed as an alternative. Maybe cryo reat them or get the interiors coated with ceramic. Maybe pick up a set of the 02+ 17/17s and you're golden...until your skill level catches up with your equipment again.

Speaking of my skill level, here's how I approach track days:

I always do an out lap at 8/10ths or less. This gets me and the tire temp up to speed, so to speak. I generally short shift, and brake a little early in the brake zones. After I come around for the second lap, I generally start picking up the pace, ensure that the tires are up to temp by gauging their grip, and also start going deeper in the brake zones.

From there I pick up the pace. By the third or fourth lap I'm using the brakes pretty hard, but being conscious of not braking deep into every single brake zone, in particular, the ones not separated by any length of straights or otherwise non-braking zones.

When I start missing my turn-in points by a few feet, I back off for a lap or so until the brake are "back under me". This is usually around 15-20 minutes into a session.

I rarely go more than 30-45 minutes at a time. When I'm ready to come in, either at the checker for the session, or still under green, I'll short shift again, stay the heck outta the way and go back down to 7/10ths or less in the braking zones.

When I pull off the track I'll idle around the paddock area 25-30 MPH for two or three minutes and not touch the brakes, to cool them. Then I'll park it. And I WON'T EVER touch the e-brake handle when I park it.

So, I think I'm treating the brakes right. Maybe my expectations are too high, since with the "other car" (2200 lbs, 128 HP; I'm sure you are tired of hearing about it by now), I can go way deep, every brake zone, every lap, for an hour and stand the car on its nose, no fade or problems. That said, I've driven with other NSX'ers with stock calipers and decent track pads and I must say they can brake pretty darned hard without any fade.

I'm still perplexed.

I ordered another rotor. I'll do some disassembly when I replace it and see if the root cause shows itself, and report back if I find anything.

Thanks for all your replies and suggestions. Most appreciated.

 

[Ponyboy]

I rarely go more than 30-45 minutes at a time.

Wow, I think that may be the root of the problem right there. In my experience, staying out on track for 30-45 minutes is a very long time for an HPDE session. Make no mistake, I'd do it if I could but our local track limits the sessions to 20-25 minutes tops (depending on carnage).

The rationale is that at around 30 minute mark is when stock brake systems and DE driver's minds start to fade. Not to mention general physical fatigue as well. It's better to save the car and driver before fatigue and oversized testicles take over.

I've done one track event, only one, in which we got to stay out for longer than 30 minutes a session and that was with a professional driver in the passenger seat.

If you're going to routinely do 30-45 minute sessions, then I'd recommend going to a big brake kit. For reference, here's the difference b/t size of rotors:

 

[nsxnut]

Speaking of my skill level, here's how I approach track days:

I always do an out lap at 8/10ths or less. This gets me and the tire temp up to speed, so to speak. I generally short shift, and brake a little early in the brake zones. After I come around for the second lap, I generally start picking up the pace, ensure that the tires are up to temp by gauging their grip, and also start going deeper in the brake zones.

From there I pick up the pace. By the third or fourth lap I'm using the brakes pretty hard, but being conscious of not braking deep into every single brake zone, in particular, the ones not separated by any length of straights or otherwise non-braking zones.

When I start missing my turn-in points by a few feet, I back off for a lap or so until the brake are "back under me". This is usually around 15-20 minutes into a session.

I rarely go more than 30-45 minutes at a time. When I'm ready to come in, either at the checker for the session, or still under green, I'll short shift again, stay the heck outta the way and go back down to 7/10ths or less in the braking zones.

When I pull off the track I'll idle around the paddock area 25-30 MPH for two or three minutes and not touch the brakes, to cool them. Then I'll park it. And I WON'T EVER touch the e-brake handle when I park it.

So, I think I'm treating the brakes right. Maybe my expectations are too high, since with the "other car" (2200 lbs, 128 HP; I'm sure you are tired of hearing about it by now), I can go way deep, every brake zone, every lap, for an hour and stand the car on its nose, no fade or problems. That said, I've driven with other NSX'ers with stock calipers and decent track pads and I must say they can brake pretty darned hard without any fade.

I'm still perplexed.

I ordered another rotor. I'll do some disassembly when I replace it and see if the root cause shows itself, and report back if I find anything.

Thanks for all your replies and suggestions. Most appreciated.

It sounds like this may be a problem with the after market rear rotors you are using.

Later,
Don

 

[dquarasr2]

Wow, I think that may be the root of the problem right there. In my experience, staying out on track for 30-45 minutes is a very long time for an HPDE session. Make no mistake, I'd do it if I could but our local track limits the sessions to 20-25 minutes tops (depending on carnage).

The times I've had problems with the NSX I know for sure I've only done about 20 minutes at a time, for whatever that is worth.

 

[Willie Gee]

I am having serious issues with my S2K using the Cobalt GT-Sports. It could* t pads. When did you purchase them? If they are significantly quieter than they were before you could have an issue as Cobalt Friction has changed their formula.

For my complete story please read the following thread: http://www.s2ki.com/forums/index.php?act=ST&f=1&t=537024

 

[dquarasr2]

I am having serious issues with my S2K using the Cobalt GT-Sports. It could* t pads. When did you purchase them? If they are significantly quieter than they were before you could have an issue as Cobalt Friction has changed their formula.

For my complete story please read the following thread: http://www.s2ki.com/forums/index.php?act=ST&f=1&t=537024

No, mine are the "original" formula.