Let me preface this post by saying my ABS lights turned about about a week ago and I have yet to find which sensor it is but I'm 98% sure that's what the problem is.

This summer began with me starting my track sessions at Heartland Park. Since then I've revisited 4 times and have been to MAM twice. Needless to say I'm hooked. The down side is I cannot get a brake setup that I have a lot of confidence in.

I started out with Stoptech ST40's and 13" rotors with Ferodo DS2500 pads in the front and non-brembo calipers and Hawk HPS pads in the rear. The balance was okay but it was a rear pad eating setup and I was having occasional fade.

Then tried Hawk HPS+ pads in the back for a little higher temp pad and flush and bleed the brake fluid with fresh ATS blue.I still consumed the rear pads in less than an hour of track time. Again the balance was fine. I’m still battling the occasion brake fad at the end of sessions.

At this point I'm fairly irritated so I break down and buy a rear stoptech ST22 kit and load Carbotech XP12 pads on all 4 corners; which are 2000 degree torque monsters, and add some front brake ducting. It's now at this point the pedal feel on the car is much much more firm. I like this. I go to MAM and begin my bed in sequence. 2 laps at ~50% and 1 cool down lap using as little brake as possible. Then I run them till they fade....I'm very excited. Knowing of course I need to mind the fact that I'm without ABS and need to keep from flat spotting the tires. I hit the first straight section, go flat-out to just about 125MPH I begin to apply the brakes, plenty early just to get a feel for the first hard stop, and the rear instantly shoots out and the car goes into an uncatchable slide sideways NASCAR style. Luckily the car went off course in a direction with lots of runoff room.

So I now spend the next 3 sessions learning how to threshold brake with huge amount of rear bias. I get okay at it but still get the rear tail wag occasionally. Still not happy I remember I have a set of Stoptech street pads for both the front and rears. I let the car cool, grab some lunch and then swap the rear street pads on, knowing full well they'll probably be gone within the hour.

The balance was much better but still favors the rear. I ended up cording out my BFG R1's about an hour later, and the pads were still holding up okay so I throw on my street tires, ‘cause what the hell, I paid for the entire day. Now I have staggered tires 265/285 vs. 255's all the way around. I actually had much more confidence with the street tires and ended up only about 1 second off from my best lap with the R1's. This leads me to believe I need to run staggered tires next year.

3 months later, I’m not any further ahead than I was. I need to play with different brake compounds to help things out but I still think I’m going to need to get a proportioning valve or something to regain my faded confidence in my brakes.

DONE!

 

This sounds like you are running with VDC turned on..... Are you disabling VDC for the track?

 

something isn't right man

perhaps you are getting some wicked knockback in the front which is causing your rear bias issues. i noticed a lot more knockback when i went to 2pc rotors. hpt is bad for knockback given the lack of braking and hard right/left of the last 2 corners followed with the long straight. given your speed, mam is the same way.

have you completely disabled the vdc? maybe change to a 14" front setup. let me know if you want to give it a try--i'll let you borrow the brackets and rotors.

 

Mine has no VDC to be disabled. Plus with the ABS light it kills all TC, ABS and VDC. I'm gonna call it a year. I don't have tires to track on other than my Hankook RS3s and the new rear BBK has a thicker hub than stock and pushed out my rear wheels enough to make the 285's rub pretty bad. Time to roll the fenders!

 

Also, I'm not familar with knock back? I'm assuming it's something to do with the floating rotors moving under heavy loading?

 

it mainly has to do with caliper mounting location and wheel bearing play, but 2pc rotors magnify it.

http://www.stoptech.com/tech_info/wp_knockback.shtml

Z33's are pretty bad about knockback. it's why you'll always see me left foot brake at the top of alpha zero--coming down the hill and having the pedal sink with no brake torque is a scary feeling.


i also remember watching a best motoring vid where the mines Z33 had a wheel speed sensor get contaminated with diff fluid. it caused the brakes to lock up and send the car into the wall. i would start with proper diagnosis of your abs issues.

i have the cipher software and cable if you need to get codes. i'm pretty sure it will read abs.

 

Ah yes! I know exactly what you're talking about after reading that article. I get that going onto the 2nd straight at MAM. I've always wondered why I have so much brake travel in that braking zone and no where else. This makes much more sense now.

And yes. I need to get the ABS fixed before anymore track play.

 

i would check everything around the diff, iirc you installed a nismo lsd a while back. perhaps something is afoot.

you get used to the knockback---it's part of the cars character.

 

Yea the diff was my first thought too. The pass side axel stub has no retaining ring on it because long story short I don't have nismo stubs but I've never had an issue with them pulling out. I check them weekly and it's alway tight, dry and in tact.

Will your code reader point to a specific sensor or just verify there is a bad one?

PS Alpha Zero is my all time favorite corner! You can make up for huge amounts of power the Z doesn't have and look like a hero coming into turn 1.

 

A0 is a blast. last year i would follow a Nismo Z over it and you can really tell the difference in down force--it was amazing how planted his car was vs mine. a big wing is on the list.

the cipher software will read like a factory consult. i'm pretty sure it does abs, i remember it picking up specific steering angle sensor faults on my car.

 

At some point I want to do some aero work too but until I get the basics all working correct I don't see the point.

Well I try the software when you have a chance. If nothing else I just like playing with it.

 

This is your issue. Move to XP10's on the rear. The 12's have too much bite for the rear axle.

Chris

 

Well i do know i had a hard time with braking when a ran a 275/40-17 non stagger. My car is so much easier to drive with 275/40-17 front and 275/40-18 rear. I would think it takes a bit of suspension work to set the car up to it handles properly without the stagger in height. Also the bias/abs etc etc is setup for a stagger in height.

 

I ended up trying some Stoptech street pads that day too in the rear and I still had rear bias issues. I was hoping that was the case too.

 

I agree but the car was fine with the square setup untill I went to the rear stoptech bbk. Although I'm going to run a stagger next year just to try it on r-comps.

 

You have probably already have done this, but I would suggest bleeding the fronts yet again. One small bubble can wreak havoc on track days.

Chris

 

Just a thought, but are you positive you have the correct rear kit for your car (and front kit for that matter)?

I don't see what year car you have in your post, but if you have an 03-05 front kit with stock rears on an 06+ car, it will be too rear biased, as would an 06+ rear kit with 03-05 front kit. They are different enough that it will be hard to dial out any bias with pads, especially without ABS and EBD to help you.

 

I think this is probably the case. I bought both the front and rear kit used. The front kit claimed to be for 06+ but who knows. All I can claim is the bias was fine with just the front kit but when I added the rear it all went to hell. This leads me to think I have a 06+ front kit with a 03-05 rear kit.

PS I have a 2006 Enth. No VDC

 

If you had the 03-05 rear kit, you would not have any issues as the car would be too front biased and you are reporting a clearly rear biased condition. My guess is that you have the 03-05 front kit since you reported noticeable rear pad wear and fade with the front only kit installed. The added efficiency and heat capacity of the rear BBK appears to have made the condition more noticeable, which is why you ended up swapping ends in the brake zone on track. If you have the means, shoot me a PM with the piston sizes (info on how to measure them without removing them is available here http://www.zeckhausen.com/How_to_Measure_Pistons.htm) or even the lot number which would be stamped on the caliper body between the pistons.

 

Okay I'll do that and get it to you. May be a few days, I'm moving this week and ovbiously that will be consuming my time through the weekend.

However, lets assume the worst and say I have the wrong front calipers. Is the only fix getting a new caliper set or is it a simple piston replacement? I'm going to rebuild them this winter anyways so that would be an easy time to swap components.