I think my brakes are $%^&*, need help figure out what the hell is going on
 

It's been 3 years since I took the Z to the track, the car drove like how I remember and I ran reasonably well. Here is the problem I do have. At every corner of the track, the brakes seem to behave differently. I would either get no pedal, stiff pedal, stuck pedal, pulsing pedal or whatever. Every corner is different, I had absolutely no faith in them what so ever. Unlike the handling, the brakes definitely felt worse than before. It is getting to a point where it isn't safe anymore, I want to see if anyone can help me figure out what exactly is wrong. I was doing Laguna Seca, I figure I will give the turn by turn break down.

Before I start, I do have the brake duct kit with Carbotech XP10 and XP8 and Castrol SRF fluid. Fluids were all fresh, pedal stiff as a rock. At no point did I get fade, so I don't believe I was overheating them. I run RS3 and I am on stock power, just springs shocks and front sway bar

Back to the track.

Going into T2 at 110mph? Braking at a little before the 3 marker, the pedal would initially not bite and then bite hard to slow the car with a little wiggle side to side. As I downshift, I can feel the pedal staying low (without me pushing it) and then it would eventually come back up as I get ready to go back on the gas. This is already weird behavior 1. The bite of the brake is just weird. I hate how I feel the initial bite, nothing and then the brakes just grab hard.

T3 and T4 I barely tap the brakes, so skip those.

T5 is a huge problem area for me. As much as I try to hit the brakes after the bridge, a lot of times the car would just go into semi ice mode where the brakes would bite and then it would let go and eventually come back again. I tried to go in with the pedals soft and then hard, both ways they would do the same thing. Like T2, I would get the initial soft bite but instead of the hard braking after, the stupid brakes just doesn't seem to grab (I don't feel anything weird with the brake pedal).

T6 I am too busy pooping my pants trying to take it as fast as I can, not on the brakes that long other than setting the car up.

T7 is another problem area for my brakes. As I hit the brakes hard, every lap the car would do something different. Sometimes it feels like it would just keep going, while some laps the car would slow down and make the corkscrew. I do seem to recall I have hard pedals every time, but it is scary when you hit it and the car simply doesn't slow down.

T9 and T10 the pedal feels okay, but once again I really have no trust in them as they can vary in feel every lap. Braking distance is very short anyway

T11 hairpin is as big of a problem as T5. Instead of the initial bite and then slowly not grabbing, I usually get into this turn with no bite and the car would go straight into ice mode. Couple times I feel like the car would just keep going straight and I used the clutch to slow down a few times as self preservation. I didn't try to reapply the brakes as I am too busy not crashing, but the car does the ice mode basically every time in this turn no matter how hard or soft I hit the brakes. Without it, I feel like I can brake as late as 2, but I usually brake at 3 marker just to be safe.

Anyway I love the car, but the brake problem is really scaring me. Anyone have any idea as to what it could be? I guess I can try the pads first, but could the ABS computer be going dead too?

Check pad condition .. have been bedded correctly ?
Check rotors for glaze
Pulsing pedal suggests ABS activated
ICE mode suggests nannies are activated

So look to driver behavior .. are you jumping onto brakes too aggressively


Think about going a bit slower and smoother to go faster

You haven't been to the track in 3 years? Right?

Pads and rotors will need replacement, but they have meat on it. It still doesn't explain why I get these weird feeling lap after lap. Sometimes the car stops, sometimes the car doesn't. It's hard to explain, it's just different behavior at each turn and each lap. I will replace the pads and rotors and the calipers on it, but I am hoping it isn't some other components going bad. I honestly don't recall being this bad.

Smooth input, hard input, both did the same thing.

Suggest you replace the pads and bed them before replacing the rotors - bedding new pads on new rotors is usually not all that successful, best to use one "used" component rather than replace both at same time.

If you are triggering ICE-mode (your pad setup is very aggressive) you will get the symptoms you describe (rock-hard pedal and no retardation).

Only cure is to isolate the yaw-sensor .. search for "yaw sensor fix" or go here:
http://www.the370z.com/diy-section-d...er-switch.html

Yes the pads are definitely aggressive, I think the new pads I have in my garage have less bite. Still, it doesn't explain why it worked before but not now. It's weird.

I will check the pads out in a few days, let's see if I have any pads left. I had 60% when I started.

Could this be caused by bad caliper? I am especially concern at the instance where the brakes bit and then just gave out, not in the same way as ice mode where I get nothing from the start

Use a pad retractor to see if you have a seized piston

You would have seen leaks by now

Have you bled the system - unlikely as the pedal would never by hard with air in the system?

Me confused !! same as you

I haven't removed each individual pad yet, but doubtful one is stuck as nothing has gone metal to metal yet. I did bleed all the calipers and there should be no air in it. Before I started the day, pedal was as hard as a rock. After the track day, it has gotten a little softer.

These two statements make me want to say your overall brakes are fine. Heavy straight-line braking after a significant period with no braking it takes a second to get into temp. Maybe just some uneven deposits causing a slight side to side which was what causes the same issue for me. Got rid of my slotted brakes too which were causing issues for me due to an something unrelated.

If the computer parts of it are eliminated I would suspect it's a suspension issue because each turn is different.

I get the t2, that behaves like what I expect. The behavior I get in the other turn is totally not normal. The one at t5 was the worst as the brakes would grab and then it would just lose power. It’s totally bizarre. Going into the corkscrew, it would do it a little but not too bad. The track seems smooth to me, but I am guessing some of the bumps might have done something to it.

I run the same brakes (Carbotech XP10/XP8) without any brake ducting, and have not had any of the issues listed above.

I do have the yaw sensor mode done, and honestly its ALWAYS off because screw having the car take over when i know what im doing... Anyhow!

Do a rebleed of the system. Maybe you had bubbles in the ABS module and now theyre out and in the system roaming free, plus its never bad to bleed your brakes anyways.

Get the car up in the air, pull off the brakes and the calipers and do a nice look over. Are the seals shot, are the pistons damaged at all, are your guide pin/clips tweaked at all?( I mention this because i had a shimmy of sorts, and it was my front passenger side bracket/clip thingy that managed to bend itself. Threw it on a vice and hit it with a hammer and problem solved)

Warped rotors are a possibility from how you describe your driving, honestly with carbotechs they arent friendly, i quite hate them after having them for a number of trackdays and i will not be going back.

Just take a weekend and check over your system and it may be something small thats just causing a world of issues on track, because on your daily drive youre not driving the car hard enough to warrant them to appear.

My car has over 50 track days on it, maybe it’s bad memory, but it has never been this bad. I will swap the calipers and everything out. I am just lazy...

I may add, it might be abs sensor going bad :confused: I had ice mode even though I did the yaw sensor mod, and after some laps one of the front abs sensors gave me an error code and abs got disabled. Replaced it but no tracks until October to see if it was the problem.

How do I test the abs sensor code

Did you disable the yaw sensor?