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No Crash- had to blow by "Bus Stop"- no other cars in area.
Great 2 day event - 5 sessions a day 20-35 minutes each- lots of track time. I have upgraded to DBA rotors & Hawk Street/Race pads PLUS I brought Motul DOT 5.1 to my dealer for FULL flush of system just a couple weeks ago.
Day 2 session 3 was progressively trying to go deeper into turns and brake harder- getting confident and really pulling down speed quickly (happy with DBA and Hawk but really put a lot of wear on the rotors in 2 days) for nice entry. About 20 minutes into session started to observe some minor brake fade. Coming down front straight stopping was good but definitely increased to moderate fade. I decided to dial back and finish up last 5-10 minutes of session less aggressively and do a good solid cool down lap. After Turn #1 the next brake zone is Turn #5 entering the bus stop. Was going ~ 139 MPH (most other times @ 145/146 MPH) down back straight. Stepped on the pedal and went to the floor with maybe 10% brake effectiveness. Fortunately the Bus Stop has a bail out route but I did reenter the active track at ~ 60ish because just had no more brake to give. The corner worker had given me a point in seeing no cars and probably understanding I lost my brakes. Limped into pits and called it a day. I think the only thing that surprised me was the big drop off in braking power after Turn #1 but assume it just had time to boil up between #1 and #5 so I was toast at that point. Good news no other cars nearby but as I was only 60ish on reentry think we could have avoided another car if they were there. Next time I'll pit sooner and avoid the temptation to do just one more lap.
Unrelated I did throw 5 OBD codes- 2 misfires/ red line & 3 emmisions PLUS 2 airbag warnings (going over rumbles in bus stop messed with air bag sensors) and also overheated eDiff session 4 day 1 but after cooling off it worked fine again. A8 was fine
When you feel any oddity with the brake feel, unless it's a race, you should definitely stop doing hot laps and inspect your brakes at the paddock. Every time, in every car when I had brake fade, I only had 1 or 2 corners with odd brake feel before it got much worse. I think it starts feeling weird right when you start boiling it, and a few minutes later, there's now so much air in the system.
The idea of street/race pad is very dangerous since its fade resistance is still much lower than a real race pad's. StopTech also has a similar pad, and it's also known to give up despite its temp range specs would suggest.
Finally, if you lose brakes, just in case you don't already know, you should immediately start pumping until you start having enough brake pressure again. Stomping on the pedal won't help.
Finally, if you lose brakes, just in case you don't already know, you should immediately start pumping until you start having enough brake pressure again. Stomping on the pedal won't help.
Ditto on the pumping of the pedal. The car has a dual brake system so even if you have a brake line break pump that pedal and you may get the other half of the braking system to give you sufficient stopping power.
The only issue with a lot of car's and the Corvettes dual brake systems is they are a dual diagonal system Vs front and rear. If you happen to boil the fluid in both front calipers you blow both sides of the dual system. Then you really need to pump the pedal to compress the air/steam in the calipers to build brake pressure.
Ditto on the pumping of the pedal. The car has a dual brake system so even if you have a brake line break pump that pedal and you may get the other half of the braking system to give you sufficient stopping power.
The only issue with a lot of car's and the Corvettes dual brake systems is they are a dual diagonal system Vs front and rear. If you happen to boil the fluid in both front calipers you blow both sides of the dual system. Then you really need to pump the pedal to compress the air/steam in the calipers to build brake pressure.
Bill
Anyone seriously tracking their C7 should at the very least have high-temp brake fluid in their system.
Castrol SRF & Motul 660 work very well.
5.1 (and stock/street pads) won't cut it if you are doing aggressive braking.
I lost brakes once using "good" street fluid. Screw that. Just do a complete flush with motul 660 and never worry about it again. It was absolutely terrifying.
Also, no street pads are really adequate for true track driving, especially off street tires. Street pads give you no warning when they decide to go.
I lost brakes once using "good" street fluid. Screw that. Just do a complete flush with motul 660 and never worry about it again. It was absolutely terrifying.
Also, no street pads are really adequate for true track driving, especially off street tires. Street pads give you no warning when they decide to go.
Most people get better results with RBF600 than RBF660. RBF600 has better wet boiling point, which makes it more resilient in the long tern. (RBF660 would perform better if you, say, were to replace it at every event).
Anyone seriously tracking their C7 should at the very least have high-temp brake fluid in their system.
Castrol SRF & Motul 660 work very well.
5.1 (and stock/street pads) won't cut it if you are doing aggressive braking.
Motul 5.1 is NOT a good track fluid!!! It only has a dry boiling point of 522°F!
I used to use Motul RBF 600 (dry boiling pt 594°) and found it to be VERY good. Motul RBF 660 has a dry boiling pt of 617°.
So...the 5.1 isn't even close to being in the same league as the "RBF" Racing Brake Fluids!!
Originally Posted by daleong
Isn't DOT 5 fluid not recommended to be used? Believe it's called out specifically in the GM track set up guide.
DOT 5 fluids are silicone based. DOT 5.1 is a designation for standard non-silicone (usually glycol ether) based fluids that conform to the boiling point, density, etc., standards of DOT 5. Some may be up to DOT 4 racing fluid standards, but as you can see with the Motul 5.1, they may really only be a very good fluid for street use.
As I said, I used to use Motul RBF 600 and found it to be excellent, but I decided to use what is arguably the best fluid available - I now use Castrol SRF. There are a couple other fluids that compare favorably with the SRF, but I've found the SRF to be really great.
The SRF dry blg pt is 594° (there are some others with higher), but the wet blg pt is 518°, and there aren't many others that are that good. That's essentially the same as the Motul 5.1 DRY blg pt!!!
Bottom line - when taking the car to the track, get a good DOT 4 racing brake fluid!!!
Just MHO, your mileage may vary!
Take a look at the Stoptech white paper bulletin on brake fluids "Brake Fluid 1A":
I used Castrol SRF on my CTS-V. Never let me down hitting 150mph at VIR. I changed the fluid completely each season and just bled in between events. Castrol + DTC 60/70 made my V bullet proof. I'll be doing the same with the Z.
Brake fluid is the weak link in any system... as suggested use full-bore Dot 4 racing fluid.
Plus air and/or moisture in the fluid will cause extreme brake fade. and Dot 4 will absorb water over time, so it must be changed regularly (6 months or so).
Brake pads are the second point of failure. I use stock Z51 pads, and have had no braking issues, but I'm only driving 9/10 HPDE speeds. Proper bedding procedure is also critical... although the newer compounds are very forgiving, follow the MFG recommendation for break-in.
Also, tires matter. With an ABS car, tire fade can cause this... if the system detects slippage, it will shut down pressure to the brakes (some call it "Ice Mode"), but it is not brake fade... it is loss of tire traction... you can jam the pedal through the floor, but the brakes will not operate.
Finally, Watkins Glen is very easy on brakes. Maybe you are also using the brakes harder than necessary.
Ok, just another take, If you have PTM, in Sport 2, the Stability Management System may still be active. THis uses the ABS system to apply Differential Braking to manage yaw on the car...
When driven under high performance track conditions, this system applies the brakes to stabilize the car.. this pumps additional heat into the braking system, even if you are not applying the brakes.
Finally, Watkins Glen is very easy on brakes. Maybe you are also using the brakes harder than necessary.
Not in my experience. I used to run the Glen 15 to 20 days per year then moved South. Now I run at VIR. VIR is far easier on the brakes. Components last at least 50% longer.
Not in my experience. I used to run the Glen 15 to 20 days per year then moved South. Now I run at VIR. VIR is far easier on the brakes. Components last at least 50% longer.
Bill
It wasn't VIR that was tough on brakes it was my heavy azz CTS-V. 4,450 lbs getting pulled down from 150mph. Maybe a resident physicist can chime in but I remember mass X velocity, squared divided by competitive.......I know it's a $hit ton, give or take.
08-31-2016, 03:46 PM
Boiled DOT 5.1- Watkins Glen @ 140MPH
It only has a dry boiling point of 522°F!
Holy braking-zones Batman!! Where is that?