A couple of months ago my car did the same thing " hard pedal/not braking" mid-race...going into T10A at Road Atlanta..130 MPH

Managed to save it by going through the gravel pits but destroyed 2x wheels and tires coming back on the track @ 70 MPH. So replaced the wheels/tires and both side tie rod ends, both side wheel bearing, and all ABS wheel sensors.

Car worked fine at the next event...but who knows...I don't trust it anymore..

 

Sure - I know your opinion on the square setup (terrasmak) and how it could contribute to this.. So you won't be surprised.

Wheels - 18x9.5 on all four
Tires - Dunlop Star Specs ~4/32 tread 275x35 on all four
Pads - Pagid RS19 front, Pagid 4-2 rear
Brakes - Stoptech ST40front, OEM Brembo rear (had the stoptech kit ordered to match the brembo rear - confirmed with stoptech)
Suspension - stock shocks, Cobb springs, Cobb swaybars stiff front, loose rear.
Laps - two warm up laps, 4th hot lap
Session - 2nd session of the day. 1st session was 3.5hrs earlier. This was day 2 of a new time trial event that took place during a race weekend. First day had 2 sessions (~15mins of hot lapping)
Track - Waterford Hills Raceway in Clarkston, MI
Conditions - beautiful. ~80degrees, mostly sunny all weekend.

The pedal felt normal if I recall. Pressure. I do not recall an abnormally stiff pedal.. that seems like something that would stick out in my memory if I couldn't press it down normally. Just no braking.. I think lifting and re-applying did something since you can hear a tire chirp just before i left the pavement.. but as you can see.. the car still wasn't braking.

No issues all weekend. I felt great in the car all weekend. No issues. No signs of trouble. I would say that I have never felt better on the track in this car in my short career than I did this weekend.. Something clicked for me.. which makes this incident so much worse.

I just got the car 'perfect' for me recently.. I have been improving a lot as I think I felt a real connection with the car (faster for some, I think slower for me). This was my 28th track day since 2007... taking all of 2011 off. I think I heard that an experienced 350Z driver with Hoosiers/full suspension runs around 1:17-1:18 on this track. I was running 1:23s on star specs this weekend.

edit - also to note. I did replace the front hubs at the end of last season.

 

Wow, that just sucks, thekinn. You're doing everything right, you're getting better, and then this happens. I really feel for you.

How bad is the car?

 

Wow, that is impressive. The photos are amazing as well. Good job on them to whom ever took them. Glad the guy is alright! thekinn, that really sucks. I hope you can get back on the track with confidence. Keep us updated!

 

I had a HARD pedal, it didn't want to depress at all. Of course all this happen is a few terrifying seconds...but mine was hard..

And I am also running the dreaded Square Setup: i.e., full Spec Z race trim with 275-35-18 all around

 

Does terrasmak have something against a square setup? I switched to one two years ago. Any problems with it, other than it tends to want to get the back end out more?

 

I've had 2 hard pedal fails on mine, I really think it has to do with the square tire setup. I never had problems with a height staggered setup. I'm glad ABS control units sell for top $$$ when I rip mine out.

 

Thekinn if it isn't too late, pull the codes and see if you had a wheelspeed sensor issue. So far it seems like the common thread for hard pedal major incidents like this. Do you think you would have known if the abs light was on? Also, what year is your chassis?

Do you normally stab the brakes and rely on ABS, or do you manually threshold?

btw, I'm not a beleiver in the concern over square setup. There are a lot of race miles without issues with square setups in the Z.

 

For what it's worth, I know the car in the original post here had a staggered width setup.. because I bought the wheels off him. 18x9 front, 18x10 rear. He experienced the same or similar event in his car at mid-o. He was a full T2 setup back then - exact tire sizes .. not sure.

Edit - to answer the above questions. Sorry, I disconnected the battery when I put it int the garage.. in case of loose/frayed wires. I checked for codes anyhow - nothing.

I do my best to avoid ABS. I will hear it occasionally, but not due to stabbing. I have been complimented on my smooth inputs by a number of instructors - that doesn't mean I am perfect 100% of the time.. but I think I am pretty smooth.

Edit #2 - 2006 Enthusiast. TCS off. I did not see an ABS light.

 

Just wanted to add this to the point of discussion. I have added a vacuum reservoir to another track car I own, its a turbo 4cyl with aggressive cams. This gives the car alot less vacuum than stock.
http://www.summitracing.com/parts/sum-g1461/overview/
It has a check valve and is installed before the booster. Works wonderfully, holds tons of vacuum for that piece of mind.

 

Wow scariest fairground ride I've ever seen. thank god he walked away with 'just a sore neck. Best reinforced Z I've ever seen.

 

Which springs? I can hear the wheels lock up at least once, possible twice, which could be caused by wheel hop on a hard brake zone. If so, the ABS will be useless since the wheels will just keep bouncing with no contact.

 

Cobb front and rear.

 

Do you know the spring rates?

 

Damn that's really scary. Glad you're safe, though, thekinn. Thanks for sharing your experience and set up, too.

I've been thinking of going to a square set up but stories like this are making me think more than just twice about it.

 

I should have known that would be the next question

Approximately 15% greater than stock.

So if stock is F314/R427
then F361/R491 for cobb.

 

Hmmm, interesting. I've had to replace my ABS recently, and similarly my calipers. I didn't have any hard pedal failures though. I guess I am just lucky? Usually, the issues start creeping up after my track day or while leaving the track, or just after my final run.
I have an 03 base model with single piston calipers and no traction control. I got lucky off ebay. Got dual piston calipers and an ABS unit for cheap! terrasmak, would you suggest I go back to a staggered step up? I am running 17x8 all around ATM.

 

I'm curious if people experiencing this had removed their splash shields without shimming the wheel speed sensors? The sensor will rub without the extra width of the splash shield, I've seen the wear first hand on the front wheels. I imagine this could wreak so havoc with the ABS.

 

This is obviously apples and oranges, but I have had similar issues with my company truck/ tow vehicle. Hard pedal, virtually no brakes, no light on the dash to indicate warning (initially). Turned out to be front ABS sensors. I had removed the backing plate when I replaced the front wheel bearings/hubs. The sensor wire was lightly being touched by the rotor as it spun. The backing plate held down the ABS sensor wire. Reinstalled plates with new sensors and I'm now without issue.
My problem was inconsistent, happening randomly in different driving and weather conditions. Luckily I wasn't towing anything when it was happening. When the sensor wire finally cut all the way through, it threw an ABS light. Which was my indicator of the issue. I'm not saying all you guys are having issues cutting the ABS sensor wire, but if they were becoming grounded or shorting out due to brake heat melting a part of the sensor, it could be the issue. Different vehicle, same issues/symptoms, ABS sensor related, which is one of the major guesses around the 350z track community.

My 2 cents; change the sensors and if you're not running backing plates, shim the hub or sensor.

 

How so?