VRMMMM

I took my car to Willow springs today for the first time. I have been to this track several times with other cars, and really enjoy the track. I first went out in my run session, and was amazed at the C7s ability, simply amazing track car! I was in Track mode/Sport.

My friend was there with his 2014 AMG C63, I had noticed he pulled in after 3 laps, I took my car around one more time then came into the pits to see why my buddy came in early. Said the C63 overheated and went into limp mode, this is a car with 2500 miles on a 68 degree day WTF!!

I tell him we still have 10 mins in our run group and to try out the C7, so we take the car out with my friend driving. He does the first lat at about 6/10th to get a feel for everything, 2nd lap he starts pushing a bit harder about 8/10s. Everything is good, no fade, no smells, just running perfect.

On turn 8 which is a long sweeper, we are going about 95mph, we reach the braking zone, my friend hits the brake, and NOTHING! We go straight off the track, not turning, in the dirt. Without taking his foot of the brake he starts to pump the brake pedal, and the brakes come back. He gets the car stopped, we took the car directly to the pits to check it out. Fluid is fine, not boiling, nothing seems wrong.

We talked to other Corvette guys at the track, mechanics at the track, nobody can figure out how this happened. The pedal was firm, so sign of fade. Just no braking zero. We had a GOPro in the car, we are going to review it tonight.

The car is fine, just got dirty. I contacted my dealer, and will bring it in for a full check up, but this seems very bizarre to us. Any thoughts or advice?

W88fixer

Z51? Cooling rotors installed? Don

VRMMMM

Z51 and cooling rotors are installed.

NoOne

ABS/TCS interfering? From what you describe, hit the pedal, feel the pedal but nothing happens?


This is one reason I hate ABS. I realize it may feel or sound like something else but you were not driving so your up to his interpretation of what happened.


Yesterday I was coming off a freeway ramp, left hand sweeping turn and a light at the very end near the end of the curve. I was moving pretty good but not enough to activate the TCS,touch the brakes to start to slow down, it pushes the pedal back at me and would not slow.


Not exactly the feeling your looking for in a high speed corner.


How long of a ride was it from realizing no brakes to stopping the car? Did you feel the brakes actuate? Lot of things happen very fast in those situations and recollection may not be the best. Nothing against him, just the way those things happen.


Were the brakes fine afterwards? No problems at all?


What was the track condition, is it bumpy or wash board there? How much steering wheel angle before he hit the brakes? Car hop or move around at all?

slief

You sure your friend didn't hit the clutch pedal instead of the brake pedal? Probably a dumb question though. The only thing I can think of would be brake fade. How were the brakes after the mishap?

That said, I spent a year racing Willow Springs on a street bike. Turn 8 would not be a fun turn to loose the brakes in. Fortunately, your friend wasn't going as fast as he could have been going into that turn. I guess it's just as well it happened there instead of turn 1 where he could have really been coming into hot. I totaled an R1 in turn 1 at 120. Walked away without a scratch but the bike was a total loss.

6spdg37s

since you weren't driving there are alota factors that can come into play with this including driver failure... could u clearly see that his foot was on the brake? maybe he caught between the pedals or the carpet or something?

VRMMMM

I will put up the video later tonight, I just got it. After watching it many times, something else is very interesting. Rev matching was turned on. The lap before going off, you can here the car shifting from 4th to 3rd and rev match is heard. On the second lap, you can hear the car shifting from 4th to 3rd same spot, no rev match is heard, and you can see no dive in the hood.

He was 100% on the brakes, because he never took his food off the brakes, he started pumping them once we hit the dirt, and they came back.

We are thinking its a programing issue, its almost like the car was cycling through ABS and stuck in the off portion of the cycle.

Snorman

What brake fluid is in the car?
It sounds like the fluid boiled, especially since "pumping" the brakes brought them back somewhat. Bear in mind, under braking pressure, fluid often doesn't boil...it's when you're off the brakes and the pressure is lower that it boils in the caliper.

Some tracks you can get away with a stock temp fluid, some tracks you can't. I ran stock fluid at Daytona, but wouldn't consider running stock fluid at Sebring, Homestead or RA. This could have happened in a few laps because the fluid, because it's hygroscopic, had a decreased boiling point.
S.

slief

I've got several hundred (if not more) laps under my belt at Willow Springs and know first hand that it's a very fast track. It's actually said to be the fastest track in the west. It's also very technical and good brakes are a must there. It's one of those tracks that is very hard on the brakes. If I were a betting man, I'd bet you hit the nail on the head.

VRMMMM

Brake fluid was not boiled. 2 laps at 68 degrees out, driving not at full tilt. There was not any fade, just suddenly Zero brakes.

VRMMMM

Snorman

Is it stock, as-delivered-from-GM brake fluid in the car?

I have had brakes feel fine the entire session, then fade slightly into a turn and be gone the next. I hope you figure out what happened, but my bet is boiling fluid in the caliper.

Also note, I was told by a "driving coach" who was with a C7 at Homestead that when running certain PTM modes, C7's are very hard on brakes. I shut off everything.
S.

wtb-z

Interesting video - videos can be hard to judge especially with just a windshield view but I would go with driver problem as well. The delta-v required to make 9 is small and can be applied gradually, as long as you position the car right. Positioning the car at extreme track left to turn into 9 is good geometry but very hard to execute.

Seapar

Dot4 fluid? Recent flush?

6spdg37s

that video was painful to watch.... is it possible the fluid was boiling and by the time u got to pop the hood it was no longer boiling?

jerryv

That's some scary stuff. Would have been a perfect time to put a code scanner on there and see if any codes were thrown when the failure happened .. Don't know if the car monitors brake fluid temps or not ..

6spdg37s

probably a good time to upgrade to steel braided brake lines as well !

mjorgensen

Could have been pad "knock back" pushed the pads away from the rotor because of flex under load through the corner before, then before the brakes would work again the pads had to be pushed back against the rotors which is basically why they did nothing on the first try. This happens in other cars, but most cars have a check ball to prevent this, maybe that failed?

rxdo

Please not a return of the dreaded ICE MODE, had this issue on my old 370z, very worrisome, basically happens as the car reads a difference in the front/rear wheel speed, usually when suspension unloads on a different part of the car. Someone can help me out on this but this is a known issue for some cars, hopefully not the vette.

AFVETTE

[QUOTE=6spdg37s;1586849723]that video was painful to watch[QUOTE]

No shitz my last time on a track was with my Z06 at Road America and I blew turn 14 and went straight off the track onto the grass, the car went off head first and I did not correct it. No damage to the car, just my pride. The car was covered in grass as was the interior. That was my last time tracking my Z.

Glad no one was hurt or your car damaged, HSDE's can be expensive if something goes wrong.

Good luck finding the problem.