Temps and Pressures on Track

[Trawz]

Looking for some opinions from the road course guys.
The first track day of the season last Friday. I did a couple mods to some important systems since last season (Z06 brake upgrade, new Mishimoto radiator, trans and diff oil changed out).
So, that day was more of a shake-down, watching temps and pressures as well as trying to stress the brakes.
It was a hot day for here in Oregon this time of year, around 90 degrees.
First couple laps of the first session out, the brakes had a slight vibration under heavy braking that went away after the 2nd lap.
5 laps in, I noticed my oil pressure was about 35-40 PSI going WOT down the main straight.
Thinking that was too low, I slowed down and pulled off to check idle pressure and to check the brakes.
The oil pressure settled at about 15psi at about 255 degrees, and this is with an aftermarket oil cooler. Do you guys see pressures/temps around there on track?
After sitting for a bit and cooling off, the pressure was normal (~25psi).

The front brakes has some strange markings down the center of the rotor.
Like there was a high spot in the center? Both diver and passenger sides had the same darker spots down the center.
I must add that after 3 sessions, the marks were gone, but when I got back home, I noticed some brake fluid was seeping from the caliper bleeders and tightened them up again.

[olblue75]

Did you bed the pads prior to your track day? An temps seem about right and what weight oil are you running??

[Trawz]

I did bed them in, plus I have been driving on them for almost a year.
This was the first time they have been really pushed hard.

As for the oil, I'm running AMSOIL 5W-30.

[olblue75]

I think your supposed to run a different weight an might wanna think about a oil cooler and getting rid if the OEM cooler.

[Trawz]

Really? Never heard I should switch to a different weight for the track.
I am already running the Mishimoto oil cooler kit.

[cdb95z28]

GM OE pads?
When did you bed them? Given enough street time after bedding, the transfer layer can be wiped off the rotor.
OE pads are a great pad but they can easily be overheated on track with our heavier Gen5s. Even the Gen6 SS 1LEs can overheat the same Ferodo manufactured pads.Throw in the variable of driver braking technique or certain track layouts and they can be inadequate. Your pic shows the pads are starting to smear, which is an indication of overheating. If not already apparent, you may be headed towards vibration from uneven pad deposits. What brake cooling do you have?

5w30 is probably inadequate. I’ve run Mobil 1 Turbo Diesel 5W40 and Mobil 1 5W50. A little more weight is a good thing, but I’m guessing there aren’t too many 90* days in Oregon.

[APR_ZL1]

Which track are running at? PIR? You should try Oregon Raceway Park; more to learn and less chance of balling up your car.

For PIR I would run a track pad like dtc70 or the latest pfc pad because of the heavy breaking zones on front and back straights. Stock pads are not good enough for a heavy car with lots of power on that track.

I run 5-40w oil, but hit the oil temp warning fairly quickly. I am thinking of adding a cooler. Also, the dic shows higher oil pressure than the gauge. If you have a way to get the pressure from the computer just to verify if the gauge is correct.

[Trawz]

Originally Posted by cdb95z28

GM OE pads?
When did you bed them? Given enough street time after bedding, the transfer layer can be wiped off the rotor.
OE pads are a great pad but they can easily be overheated on track with our heavier Gen5s. Even the Gen6 SS 1LEs can overheat the same Ferodo manufactured pads.Throw in the variable of driver braking technique or certain track layouts and they can be inadequate. Your pic shows the pads are starting to smear, which is an indication of overheating. If not already apparent, you may be headed towards vibration from uneven pad deposits. What brake cooling do you have?

5w30 is probably inadequate. I’ve run Mobil 1 Turbo Diesel 5W40 and Mobil 1 5W50. A little more weight is a good thing, but I’m guessing there aren’t too many 90* days in Oregon.

I am running HAWK HP-Plus Sport/Track Pads.
Figured I would get a good pad when I did the Z06 Upgrade.
After tracking for 2 seasons on the stock 4 pistons with race pads, I wanted more stopping power.
I beaded them in Fall 2019. Did about 1500 miles of street driving on them over the winter.

However, I think they might have been getting cooked. When I went to retighten the bleeders and clean off the brake fluid that seeped out, the brake pads were shedding the exposed back coatings like burnt paper...
I currently have no brake cooling. I was trying to get a Z/28 kit but had no luck finding one. Might have to build my own. It's defiantly on the top of the list of next upgrades.

Thanks for the info on stepping up in oil weight for the track.
I didn't know if that was safe, so I stuck with 5W-30 from AMSOIL. I'll look into some 5W-40, especially since mid-late summer regularly brings 90+ degree days here.

[Trawz]

Originally Posted by APR_ZL1

Which track are running at? PIR? You should try Oregon Raceway Park; more to learn and less chance of balling up your car.

For PIR I would run a track pad like dtc70 or the latest pfc pad because of the heavy breaking zones on front and back straights. Stock pads are not good enough for a heavy car with lots of power on that track.

I run 5-40w oil, but hit the oil temp warning fairly quickly. I am thinking of adding a cooler. Also, the dic shows higher oil pressure than the gauge. If you have a way to get the pressure from the computer just to verify if the gauge is correct.

That's right! Been going to PIR for the past 2 summer now. Its just so easy to get to.
I want to try to get to ORP this summer. I hear its a technical track that feels like a large go-cart track and the facilities have gotten better then its early days.
Its just more of a trip.

Looks like I might have to switch to a dedicated track pad. I believe my HAWKs might not be up for the speeds at PIR.

I'll definitely invest in some 5w40 here soon. Just put in some fresh AMSOIL 5W30 a couple weekends ago.

Thanks again for the advice!

[cdb95z28]

Wow, no cooling? You got lucky to not have any fluid boiling. You can piece the Z/28 duct kit together with buying the individual parts. There is a recent thread on this. I suggested to that OP about doing that and he had success. But they probably won't be enough. Lots of variables to say if they would offer enough cooling. But some cooling is better than none. Quantum used to make the dedicated kit for the Gen5 Camaro, but they do not anymore. I have a Gen6 SS 1LE buddy who tried the the Hawks and didn't like them on track. But you may have had success if you had adequate cooling. The Z ducts are engineering for the 14-15 refresh nose, but they can be made to work on the 10-13. A member here did it on his '13 1LE.

Be aware that using an aggressive track pad will require more cooling and excellent fluid. While I would not consider those Hawk pads track pads, zero cooling is trouble waiting to happen. I run Raybestos ST43 pads, the vented C7 calipers, dedicated cooling ducts that take air from the nose and ducts it to the inside of the rotor. I also run the Z/28 ducts but they alone most likely cannot cool enough by themselves especially with hardcore track pads. I also have titanium shims at the pads that help slow the heat transfer to the calipers. Castrol SRF, Endless 650 or Brembo HTC64T fluid should be used and properly maintained. Since we are stressing the braking system we must continually lay eyes on them to be sure they will slow the car without drama every single time.

Take a look at your caliper piston dust boots. You may have cooked them. While they do not "seal" the piston, they do help with long term durability by keeping dirt and dust off the piston which helps the actual piston seal. If they are cooked you can just replace the dust boots without having to do a complete rebuild. Rockauto has the Centric piston seal and dust boot kit for each caliper. Buy two kits to do both calipers.

On the bleeders. Since the bleeders are vertical and seal at the bottom at the taper, there will always be a tiny amount of fluid sitting within them after you close them. When the calipers are heated at the track , this fluid wants to push out the top or thru the threads. The threads do nothing towards sealing the bleeder when tight, it is all done at the taper. The only way to eliminate the fluid from the closed bleeder is to give them a quick hit of BraKleen to flush out that fluid. I take the red spray tip and put it inside the closed bleeder with a rag wrapped around the opening. This keeps the fluid from spraying all over your rotors, pads and yourself. Do a quick blast, let it dry and do it again. You may see fluid/BraKleen trying to percolate around the threads. Let the bleeder dry before installing the black rubber cap.


If the fluid is left inside the bleeder, this will cause other issues beyond the cosmetic effects of leakage. The fluid will be within the bleeder threads. This will absorb moisture and corrode the threads. This corrosion acts as a threadlocker, requiring a lot of loosening torque to open the bleeder. If we are lucky the bleeder won't snap.

If you bedded your pads in 2019, then the transfer layer was gone.

[Trawz]

Originally Posted by cdb95z28

Wow, no cooling? You got lucky to not have any fluid boiling. You can piece the Z/28 duct kit together with buying the individual parts. There is a recent thread on this. I suggested to that OP about doing that and he had success. But they probably won't be enough. Lots of variables to say if they would offer enough cooling. But some cooling is better than none. Quantum used to make the dedicated kit for the Gen5 Camaro, but they do not anymore. I have a Gen6 SS 1LE buddy who tried the the Hawks and didn't like them on track. But you may have had success if you had adequate cooling. The Z ducts are engineering for the 14-15 refresh nose, but they can be made to work on the 10-13. A member here did it on his '13 1LE.

Be aware that using an aggressive track pad will require more cooling and excellent fluid. While I would not consider those Hawk pads track pads, zero cooling is trouble waiting to happen. I run Raybestos ST43 pads, the vented C7 calipers, dedicated cooling ducts that take air from the nose and ducts it to the inside of the rotor. I also run the Z/28 ducts but they alone most likely cannot cool enough by themselves especially with hardcore track pads. I also have titanium shims at the pads that help slow the heat transfer to the calipers. Castrol SRF, Endless 650 or Brembo HTC64T fluid should be used and properly maintained. Since we are stressing the braking system we must continually lay eyes on them to be sure they will slow the car without drama every single time.

Take a look at your caliper piston dust boots. You may have cooked them. While they do not "seal" the piston, they do help with long term durability by keeping dirt and dust off the piston which helps the actual piston seal. If they are cooked you can just replace the dust boots without having to do a complete rebuild. Rockauto has the Centric piston seal and dust boot kit for each caliper. Buy two kits to do both calipers.

On the bleeders. Since the bleeders are vertical and seal at the bottom at the taper, there will always be a tiny amount of fluid sitting within them after you close them. When the calipers are heated at the track , this fluid wants to push out the top or thru the threads. The threads do nothing towards sealing the bleeder when tight, it is all done at the taper. The only way to eliminate the fluid from the closed bleeder is to give them a quick hit of BraKleen to flush out that fluid. I take the red spray tip and put it inside the closed bleeder with a rag wrapped around the opening. This keeps the fluid from spraying all over your rotors, pads and yourself. Do a quick blast, let it dry and do it again. You may see fluid/BraKleen trying to percolate around the threads. Let the bleeder dry before installing the black rubber cap.


If the fluid is left inside the bleeder, this will cause other issues beyond the cosmetic effects of leakage. The fluid will be within the bleeder threads. This will absorb moisture and corrode the threads. This corrosion acts as a threadlocker, requiring a lot of loosening torque to open the bleeder. If we are lucky the bleeder won't snap.

If you bedded your pads in 2019, then the transfer layer was gone.

Thank you very much for that mountain of advice!

Yes, brake cooling was next on the list.
Last Friday was the first time I have pushed the C7 Z06 caliper system since I installed them, and I felt I wasn't pushing them too hard (no deep dives into the corners... yet).
But, the whole reason I installed them was to push them harder then the stock system could handle.

Someone in the 1LE thread found all the pieces for the Z/28 kit recently, but because the kits are discontinued, the individual parts are getting hard to come by.
I'm an engineer at a fab shop and could easily design my own system, but our shop needs to be slow enough to fab them up. which doesn't look like that will happen anytime soon.

Looks like dedicated tack pads are in my near future.
When I installed the Z06 kit, I blead the system with MOTUL RBF600. Was told that was the fluid to get after you upgrade.
Where did you pick up the titanium shims? That sounds like a great idea.

I cleaned up the bleeders with a bit of brakeclean and made sure everything was dried up before it all went back on.

[gtstorey]

The Motul is a good fluid but Castrol React SRF is supposed to be a lot better.
https://thebuildjournal.com/tech-gui...parison-guide/

[cdb95z28]

My buddy fabbed up a set of ducts based off my Quantums. A short rpiece of 3" tubing is probably the hardest part to get right on these. Get the length right then weld it to a mounting plate. Honestly, someone could pound out sets of these out without any difficulty.

Here are some pics of the Quantums






I got my titanium shims from Ken @ KNS Brakes

https://knsbrakes.com/c/car-item/182...+Shims+-+Front

The Motul is a good fluid, but when you start to look at the specs there are better choices. I kinda look at what cost for confidence and zero failures? I've run the Castrol SRF, but last year I switched to the Brembo HTC64T. The Brembo has a better pedal feel, especially when hot.

gtstorey's link is a good breakdown of fluids, but it could use an update.

This associated link gives some good data on fluids:
https://thebuildjournal.com/tech-gui...view-analysis/

[Trawz]

Awesome! Thank you.

I could design up some similar system easily. Time do do some 3D modeling.

I'm also looking into doing a factory oil cooler delete, but from what I hear, its not the most fun job to tackle due to bad access to some bolts. However, someone pointed me to a blanking plate that comes with AN10 fittings to plumb in an after market system to where the factory one was.

Those Titanium plates are on order, Thank you sir!