AP Racing Sprint kit issues

[M0nk3y]

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.

[ka-t_240]

Originally Posted by M0nk3y

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.

[Kulebrero]

Originally Posted by M0nk3y

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.

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!!

[Wangspeed]

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.

[Kulebrero]

Originally Posted by Wangspeed

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 ☹️

[Wangspeed]

Originally Posted by Kulebrero

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.

[lutfy]

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.

[M0nk3y]

Originally Posted by ka-t_240

curious to see the difference here.

New



Old




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[M0nk3y]

Originally Posted by Kulebrero

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!!

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

NA at VIR

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[NoHaveMSG]

Originally Posted by M0nk3y

New



Old




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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.

[Kulebrero]

Originally Posted by M0nk3y

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

NA at VIR

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Sweet!!

[new2subaru]

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.

[JRitt]

Originally Posted by Kulebrero

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.

Who did you talk with here at Essex? I'm not sure what the miscommunication was, but driving race pads on the street would typically not cause cracking like that. It would cause accelerated wear, but a crack like that is typically due to thermal shock as others have noted. Please see my comments in the video below at the 3:00 mark.

We literally have thousands of 86 customers running our 299mm Sprint Kit without any issues, premature cracking, etc. Your experience in this case is therefore a bit rare and a bit odd.



With that said, there are a million variables at play with how much abuse the brakes take on any car, ranging from tire choice, to driving style, to the track run. It's therefore impossible for us to predict that any discs on any car are going to last X number of track days or Y number of miles (although people do ask us to make that prediction all the time). With that said, I would expect our discs to last longer than they did in your case without incident.



Based on what you've written, the Sprint Kit should be an appropriate choice for your car and what you're doing with it. I don't think jumping ship would be fruitful or economical for you.


I'm sorry you got discouraged after talking with our team. Please shoot me a PM so I can collect some more data from you. I want to understand the details and help you towards a resolution.



Thanks!

[steved]

@Kulebrero

Did you follow up?