AP Racing Sprint kit issues
 

I got a set of AP Racing Sprint brake kit last October for my 2022 GR86. Took it to one track day before the season ended and to three track days so far this year. Aside from driving to/from the track, the car is used for track duty only. Car has 4,100 miles. Got the brakes at 2,600-2,900 miles. As I was rotating the tires yesterday, I noticed the passenger side rotor has a one inch crack.

Someone please tell me these things are supposed to last more than 1,200-1,500 miles.

If not, I may need tips on other BBKs. The AP Racing kit was great on track. I had no issues at all, but I can’t buy new rotors every three track days.

Picture?

I don’t have a place to upload them

You can attach files to your post under advanced reply tab.

Without a picture it is hard to say. If it is just heat checking then it is normal. If it goes to the edge of the rotor or you can catch your fingernail on it, replace it.


https://www.essexparts.com/news-blog...-my-iron-discs

F me! $750+ to replace them after four track days and ~1,500 miles.

How do I make them last longer?

I probably should look into other brake kits.

Ugh, yes, that needs replacing. What track(s) did you run and what is your driver experience/skill level?

I don't think anyone will be able to provide much useful info without knowing what your setup is.

One day at Dominion, two at VIR, and one at Summit Point. I’ve done 20-25 track day totals. I’m not super aggressive. I engaged ABS once in the wet for the first time on Saturday.

The Essex rep suggested it is because I drove it on the street with the DS1.11 pads. But I only drove it to/from the track almost entirely on highways—not a lot of stop and go, city driving.

Will they last only 5-6 track days otherwise?

What do you meant setup?

2022 GR86.
Suspension: Tarmac2 coilovers, sway bars front and back, camber plates, rear LCA, end links.
Brakes: AP Racing Sprint kit, SS lines, fluid.
Tires: 245/40/17 RS4, 6UL 17x9 wheels.

Other than that, I have an oil cooler, some aero (splitter, spoiler, hood vents), and safety stuff (seats, roll bar, harness).

I have the Radi-CAL kit so can't speak directly to your experience with the Sprint kit but I have 10 track weekends on my rotors and drive on DS1.11 or DS3.12 pads with no problems all year round.

It sounded like the Sprint kit was good enough for HPDE days when I first looked into it. I figured a $6K kit would be overkill.

Was thinking I could move up to the 325mm rotors on the Endurance kit since it uses the same calipers but it appears they don’t sell them unless you have the entire Endurance kit.

So, sounds like I need a different BBK. Any recommendations aside from the Radi-Cal?

Gen 1 Brembos use 326mm x 30mm rotors, it is very likely that the rotors used with the Sprint kit (299mm x 32mm) are undersized for Gen 2.

The sprint kit should be plenty good enough. I would contact Essex and talk with them about it, that is not normal to only last that amount of time. None of the guys I know have issues with having to replace friction rings that often. The sprint kit is the most common kit I see aside from factory PP kit.

Can you run the 325mm without the endurance kit caliper bracket? I wouldn't think so.

That is why I was asking about setup. You could be FI and swapping to slicks for all I knew.

What kind of times are you running at VIR and Summit? Summit is pretty hard on brakes. VIR a lot less so due to the long straights. Are you running ducts? Ducting in cool weather can lead to cracking or pads not reaching temp.

They said it appears normal…even after only four track days and 1,200-,1500 miles. This was their response:

“Hello,

This appears to be a disc that has seen many track days and heat cycles. This looks normal for a disc that has been used for track use and also street use with DS1.11. We do not recommend street driving with the DS1.11 because it is designed to operate under track temperatures so in street use it can be very hard on the rotor surface.”

2:13s at VIR, 1:33s at Dominion, and 1:43s at Shenandoah (not Main). It was wet all day at Shenandoah…I only did 1:43s in the last session as the track started to dry. I heard Max4 86s and BRZs were doing 1:37s to 39s yesterday with sunny skies and ambient temps in the low 60s, so my 1:43s on Saturday didn’t even come close.

I only did one day at Dominion, two at VIR (one rainy all day and one dry), and one mostly wet at Shenandoah total on those brakes. The pads still look new.

I do not have ducts.

Tell us what your warm up and cool down procedures are.
Also, what does the other front rotor look like?
And what about the inside surfaces of the front rotors?

I usually take it easy on the first and last lap as soon as I see the checkered flag, and usually though not always drive around the paddock for a few minutes after.

I haven’t engaged ABS but once in the rain, my lap times aren’t braking any records, and I’m running RS4s which aren’t the stickiest tires in the world. Based on everything I’m reading, however, it would appear I’m somehow braking harder than the average Joe. I have yet to put a single tire off track or have a spin/off of any kind even in the rain—but of course now that I say it, it’ll be the first thing to happen next time I’m on track. I don’t baby it on track, but I’m also not 10/10 out there.

It seems I need a real BBK. I may need a few days to accept this was the costliest decision of my build so far as I may need to buy new wheels and tires because my 17x9s likely won’t fit anymore.

On a separate note, I have a kidney for sale. Make an offer.

You are 1. getting the rotors very hot and 2. thermal shocking the braking system.

Based on the amount of heat you are generating, I recommend you look for a much heavier BBK, rather than the weight-reduction based BBK you are currently using.

Check out this thread, for example.

https://www.ft86club.com/forums/showthread.php?t=147978

Keep in mind that it is VERY easy to inadvertently get into ABS on a modern car without even realizing it. You may not even feel the ABS engaging, as modern ABS pulses very quickly, and you only really get the crunchy feel when you're DEEP into ABS.

Weight reduction wasn’t my goal. I was looking for something better than stock but not overkill…erroneously thinking that anything bigger would be overkill.

I had a Miata before with stock brakes and $80 pads. Used it and drove it the same way as the 86. Never had a brake issue. 12-14 track days after, the pads still had more than 50% left and the rotors were perfectly fine.

When asked if I’m engaging ABS when braking, I can say I’ve only felt it once in the rain. I can’t say it has never happened otherwise, but certainly not enough to notice it.

I’m sure thermal shocking is directly related to the premature damage to the rotors, I just don’t know what I did.

Not that I’m policing every person on track, but I haven’t noticed doing anything drastically different than anyone else as far as picking up speed on the first/second lap and cooling down on the last lap and on the paddock.

I’ll take whatever advice I can get to help prevent this in the future because at $700 per rotors every three track days, I’ll have to quit the sport. What am I doing to thermal shock the system?

Have you talked with other owners in your area about what they are running? That is usually where I start when I have questions.

These are $299 per rotor from Essex, if I’m thinking these are what you are referring to.

AP Racing J Hook Competition Disc Replacement Ring (11.75" x1.25" / 299x32mm)- Right Hand, 60 vane
Part #: 13.05.10084
Brand: AP Racing

AP Racing J Hook Competition Disc Replacement Ring (11.75" x1.25" / 299x32mm)- Left Hand, 60 vane
Part #: 13.05.10085
Brand: AP Racing

Most folks will warm up their mind, as well as their engine and transmission on the outlap, but often times forget about their brakes. Ideally, you want to gently accelerate, and brake, repeatedly, on the outlap, to input small amounts of heat into your braking system to bring them up to temp, rather than just taking it easy on the outlap, and then suddenly going full threshold at the first braking zone of your first lap.

So, the discs were thermal shocked, overheated, abs was going off constantly causing excessive heat or they were driven on the street with a pad that was too aggressive, according to the supplier.

:iono:

A too aggressive street pad will cause increased rotor wear, but not cause the cracking. The cracking is is pretty much all thermal shock.

Agreed 100% yet the OP was told the aggressive pads could cause the cracking, unless there was a miscommunication.


I can't get my head wrapped around how a 32mm wide rotor, after just 3 track days, could overheat and crack like this. It's hard to imagine that these discs couldn't take anything thrown at them. Short of being tossed in water after a hot run, I just can't comprehend how this happened.

I don't get it either.

So context for someone who is actually running AP Sprint Kit.

My last set of rings lasted 9 track days, 4-5 20min sessions each time. IE - A lot of track time.

I run ST43s this time around, prior I've ran DS1.11s on my first set of rings. So - the fact you're cracking these quite severely in limited outings is concerning/interesting, whatever you would like to take away from it.

From the photo you listed, you don't seem to have much, if any minor heat stress indicators/minor cracks throughout the rotor face. These are normal, as that's how they dissipate heat. Not seeing these really present yet seeing an actual crack seems odd. Much kind of what Mike mentioned, thermally shocking them or not properly bringing the pad/rotor up to temp together (DS1.11s work really well cold, so I can see this being an oversight). Also seems like you have pad smear or something on the rotor face. It's not completely clean, or at least appears to present that way

Anyways, my car is similar to yours. Aero F/R, I run 225 or 245 R7s and I am not kind to the car, VIR Time is 2:07.8. 2016 FRS, NA, E85

The old rings that I cracked vs the new ones are designed slightly different. The new rings do not have cut-outs/balance area on the internal face where the vanes reside. It's completely solid all the way around. I'll take a photo of my spares to show what I mean.

curious to see the difference here.

Wth then?

I don’t get it.

I did run two days in variable conditions. Started raining in the morning, drying in the afternoon with puddles here and there. But if ruining your brakes is as easy as driving in variable conditions, we’d all get bad brakes on rainy days. No?

Btw, are you FI or engine swap? Either way, 2:07 at VIR is a heck of a time. Nice!!

Stick with prolific 17x9 wheels and if you aren’t willing to test again, get a Brembo BM4 kit from CSG. There is a lot of thermal mass available due to the one piece rotor.

You can go all overboard with some really big kit but you may find the brakes too sensitive. Plus it’s just extra weight. And 18” wheels and tires are more expensive.

Really the only complaint I have about the BM4 is the use of bolts instead of studs, but that is fixable. See my build thread.

This may be the way.

Can you tell me about the bolts instead of studs issue? No idea what that means ☹️

BM4 is a mono lock caliper without a removable bridge. Since Brembo includes bolts that secure into an aluminum adapter, it may fail over time. I’m personally not a big fan of frequent threading into aluminum.

I found some pricey Tarett studs made for Porsches that come with bolts to hold fixed calipers. Too many people had problems with their aluminum knuckles stripping. The cheaper alternative is to have the caliper adapters drilled and fitted with Timeserts.

There's one other advantage with studs. You can remove the nut, add a thin threaded sleeve? And slide the caliper into a service position instead of completely removing to access the pads.

A few of us had similar issues with the Stoptech C42 kit (lighter rotors = shorter life). The rotors would not last long (ie max 3 weekends on average). Granted ST came out with the vaned (directional) rotor replacement but longevity as still not there (4-5 weekends or 20ish sessions).

Here was the solution: https://www.colemanracing.com/Brakes...m-Brake-Rotors

1) You send in your current rotor ring.
2) They measure the rotors and add it to the system (you will not have to send the rings again).
3) The new custom rotors were a touch heavier and the vaned walls were also thicker (measured).
4) It was also heat treated meaning less prone to fracture.

Another competitor (NASA TT5 S2K who is very fast and holds a few lap records in the region) has obtained over 72 sessions (session can be anywhere between 15-20 mins including TT and instructor runs) without issues. These are also plain rotors (no dimples, drills or slots).

When I run out of my rotors (spares), that is the direction I will be going.

PS: Have had years of positive experience with Coleman, they make rotors for NASCAR teams and Prodrive.

Cheers.

New

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Old

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Yeah, just saying, my experience yours does not certainly match up

NA at VIR

https://youtube.com/watch?v=9Nb1HsZDpDg


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Looks like from they did that for balancing. I wonder if they stopped doing it that way due to it creating a stress riser at the cut. I have seen that machined cut on other rotors before and I have always assumed that is what it is for.

This is just my speculation anyway.

Sweet!!

This is the first time I'm reading about an issue with the sprint kit here, or anywhere for that matter. I don't like the response you received and I would reach out again.

That said, maybe you shouldn't throw the baby out with the bath water and get a set of rings. Talk to the manufacturer about your brake pads and how you can better mange your braking. There could be a learning opportunity here.

There's also the possibility that they were defective and this is a "one off" No need to spend more money on another kit if this will do you in the future.

I would give it another shot, personally. If you decide to give them another try please report back.