I ran CSG CP pads in AP 9660 calipers on track with my ZD8

[Pat]

I'm sorry to waste everyone's time with this post. The information is incorrect. I ordered the CSG CP compound, and was provided the CP compound for the rear brakes, but SP for the front. As CSG doesn't have the SP or CP part numbers on their website for the 9660 calipers, I was unable to verify I was shipped the correct parts. Additionally, I ordered the parts through a local shop and had that shop install everything, so there was one more link in the chain. The whole thing just sucks, as the brakes didn't behave as expected, and I didn't get the parts I paid for. And now I've wasted even more of your time. I was trying to help the community by providing guidance to those that were considering the CP compound on the 9660/355mm kit, but failed. <fart noise>


Context: I had a ZD6 for eight years. I put 135,000 miles on it and maybe 130 track days. I've probably driven eight to ten different pad compounds on track with first-generation 86s. My favorite track-specific compounds were CSG C2 and Hawk DTC-60s. I ended up using the Hawks regularly because I thought they were a better value. Most of my experiences were with the AP Sprint kit, but I also drove a few other brake kits. There were a wide variety of tires, from basic all-seasons up to true racing slicks.
I bought a ZD8 in March of this year. I knew I wanted an aftermarket big break kit to keep track temperatures down. I enjoyed the AP Sprint kit I used for several years, but found myself replacing rotors annually due to the stress cracks induced by the heat. I knew I wanted something bigger than those 299 mm rotors. I considered going with the AP Endurance kit using the same 8350 caliper and 325 mm rotor, but decided to go with the newer-technology 9660 caliper and 355 mm rotor instead.
Now that you have the background, I'll get down to why I'm posting this. I've always run street pads on the street and track pads on the track. When deciding which pads to run on my fancy new BBK, I consulted a couple people I respect for multiple reasons. Both know much more about brakes than I do. They both told me I could very likely get away with running a single brake pad year-round. They both thought I could use the same pad to so ski in the winter, daily drive in the summer, and use in competition at race tracks. I was skeptical, but thought, "Hey, I trust both of these guys. They're good dudes and know more than I do." So I went with it. I considered either the Ferodo DS2500 or the CSG CP compound. While I loved the DS2500 on my B5 Audi, I really disliked driving them on a ZD6. They felt like they were made of wood, and just didn't have the bite I like. So I decided to try out the CSG CP pad.
To be fair, this pad is marketed as a street pad, not a track pad. I was told the pad would likely still work for my use case because there was so much overhead in my BBK given I drive a stock power ZD8. In theory the running temperatures, even on track, would be well within the designed operating range of the CP compound. The mass of the rotor and it's ability to dissipate heat both would make this possible in theory.
Unfortunately theory doesn't always equate to reality. I was skeptical about using one compound for such a wide variety of activities, and it turns out that was for good reason. The first time I used the CSG CPs on track I noticed the initial bite wasn't as good as what I had hoped for. It felt like the pads just didn't bite as expected for the first ~.3(?) second at the end of a long straight. After that they behaved as expected. I expect this is due to the BBK cooling so well. While I slightly preferred the DTC-60 in the Sprint kit over the CP in the 9660 kit, the difference was minor, and one I was willing to accept given the convenience of not changing pads for every track day.
I did another ten or so track days without issue. Then, at the last event of the year, I noticed I just wasn't decelerating as well as I used to in the biggest braking zones. It wasn't dramatic, but it was enough to notice. I looked at the brake rotor and saw pad smearing on it. Apparently I had overheated the pad. The last four track days were on RE71RS tires. Previously I had driven on RC1s.
Hopefully this information helps others make better-informed pad compound choices with the 9660/355mm kit. I expect for most drivers the CP compound in a 9660 caliper would work great for a dual-duty car. For advanced drivers at the race track on faster tires, stick with a race pad.
I plan on going back to the DTC-60 pad for the track and HPS for the street.

[Ohio Enthusiast]

Originally Posted by Pat

I looked at the brake rotor and saw pad smearing on it. Apparently I had overheated the pad.

What was the pad thickness at that point? The thinner the pads get the less heat tolerant they become.

Could you share some more details on wear rate (street and track) and dust and noise on the street?

[Pat]

Originally Posted by Ohio Enthusiast

What was the pad thickness at that point? The thinner the pads get the less heat tolerant they become.

Could you share some more details on wear rate (street and track) and dust and noise on the street?

Yep, they do. I haven't measured, but a visual estimate would say they are at about 40% thickness now. As expected, they wore significantly faster when overheated. There was very little wear before that happened.
Before overheating they wore very well with very little dust. As I have not removed the pads since installation, that's the only wear-related detail I can really provide.
They have been almost silent on the street. I have noticed a little more noise since overheating them, but have not rebedded them since. That might make them near silent again.

[CSG Mike]

Was the overheating after the rotors were flipped to get more heat into the brakes?

[timurrrr]

Originally Posted by Pat

Apparently I had overheated the pad.

How long were the sessions? Were you pushing non-stop?
How much did you cool down the brakes after each session?
Any ducting to provide additional airflow to the rotor?

[Pat]

Originally Posted by CSG Mike

Was the overheating after the rotors were flipped to get more heat into the brakes?

Good question. No, I never changed the rotational direction of the rotors.

Sent from my Pixel 7a using Tapatalk

[Pat]

Originally Posted by timurrrr

How long were the sessions? Were you pushing non-stop?
How much did you cool down the brakes after each session?
Any ducting to provide additional airflow to the rotor?

20 minute sessions. Sometimes I'll only drive 15 of that.
While I don't keep records of this, typical time between sessions is 90 minutes.
I did not have any brake ducts.

[CSG Mike]

After further discussion and some digging, Pat is on the SP1, not the CP, as that is what his shop ultimately ordered.

The SP1 is a true street pad designed for low dust and noise on race calipers, and intended for those who street drive their race setups with the intention of swapping to a CSG race compound at the track.

It's a testament to the capacity of the AP 9660 kit that a pad that was NEVER meant for track use survived track use with a veteran driver at the wheel.

[Ohio Enthusiast]

Originally Posted by CSG Mike

The SP1 is a true street pad designed for low dust and noise on race calipers, and intended for those who street drive their race setups with the intention of swapping to a CSG race compound at the track.

So these are like the Carbotech AX-6? Meant to share a rotor between street and track pads without re-bedding?

[CSG Mike]

Originally Posted by Ohio Enthusiast

So these are like the Carbotech AX-6? Meant to share a rotor between street and track pads without re-bedding?

It would be more in line with a Carbotech 1521.

While the transfer layers for carbotech pads are compatible, you still have to re-mate the surface of the pad to the rotor every time you change pads with Carbotechs.

[JRitt]

Glad you got this sorted Pat...I knew something wasn't adding up!