My Z32 Fronts Always Want to Lock... help?

[DuckyD]

I have been having pretty bad issues with my Z32 brakes wanting to lock at the first sign of heavy braking.

My setup:
non ABS car
decent tires
Z32 Brake Master Clyinder

Z32 30mm Alum Front Calipers
Brembo Blank Front Rotors
New'er Hawk HP+ Pads

Stock Rear Brakes
Brembo Blanks
Old'er Hawk HP+ Pads

Every time I go to brake heavily (at autocross and sometimes on the street) my front right wheel instantly wants to lock-up and it takes quite a bit more pedal modulation before the front left begins to lock.

It seems that I should be able to get more brake force before the wheel decides to lock without warning. It also seems that the wheels should want to lock at about the same braking force.

I wanted to know...
1) Is the Z32 BMC my best bet for this setup?
2) Since I had to cut out the flare fitting and install it into the BMC, and that "port" goes to the front-right, could there be a problem with how I installed it?
3) Are the pads considered too aggressive for street and autocross?
4) Wat to do?

[Def]

Too much front brake bias due to more piston area on the Z32 fronts vs. stock fronts. Front left is the heaviest corner even before you add a driver, therefore it has the most traction.

[DuckyD]

So what is the resolution?

[cdlong]

bigger rear brake rotors, larger rear piston area, adjustable prop valve (and disabled stock valve), higher friction rear pads. what size tires are you running front and rear? you could go with wider fronts if you're staggered and have the room. what do you have s13, s14? you could technically run s14 rear calipers on an s13, the pistons are slightly bigger, but not worth it since z32 calipers are the same size as s14 and use larger diameter rotors.

[jmauld]

Try a smaller master cylinder.

[DuckyD]

what do you have s13, s14? you could technically run s14 rear calipers on an s13, the pistons are slightly bigger, but not worth it since z32 calipers are the same size as s14 and use larger diameter rotors.

I am S14, running the base 350Z wheels (17x7.5F 17x8.0R)
245 fronts with like 280 treadwear
255 rear with like 200 treadwear

I always figured that most braking force was up front, so z32 rear calipers were not worth the extra money and hassel of dealing with the e-brake.

Moreso, I was under the imperssion that the brake master cylinder is going to send the same amount of fluid to the front and to the rear, regardless of what is at the other end. Is this not correct?

Also, AceinHole is using a 1" BMC instead of the popular Z32. Is that in line with what jmauld is suggesting?

[cdlong]

I always figured that most braking force was up front, so z32 rear calipers were not worth the extra money and hassel of dealing with the e-brake.

it is, but not all. if you're locking up the front prematurely you've either got an issue up front (old, hard tires) or not enough force in the rear. if you had more braking in the rear, you wouldn't have to press the pedal as hard to slow down at the rate you want. the cost is the only thing i would worry about in doing the rear. there's more too doing the rears, but it's not really harder, just longer.

Moreso, I was under the imperssion that the brake master cylinder is going to send the same amount of fluid to the front and to the rear, regardless of what is at the other end. Is this not correct?

it is, but a larger piston area will put more force on the brake pad and produce more friction. that's assuming you mean same between different caliper setups, not the same front to back. the prop valve reduces the amount of fluid going to the rear compared to the front to reduce the chance of locking up the rears in a heavy stop as more weight shifts forward.

and without knowing a great deal about your tires, it sounds like you have more grip in the rear. you could stand to go with some grippier tires in the front to get some more decel before lockup.

[ecugrad]

I have been having pretty bad issues with my Z32 brakes wanting to lock at the first sign of heavy braking.


Z32 Brake Master Clyinder


Yeah, I had the SAME problem. I bought my car with the Z32 swap F/R and a 1" M/C. Brakes were ALWAYS too twitchy. I downgraded to a Z31 15/16" MC and its MUCH better but still not perfect.

The Hawk HP+ seemed to me to not help as well. They have a hard initial bite (not so bad for R comps, horrible with street tires). I am running some stock pads right now with good results. What tires are you running?

Search on here for Z32 brake threads, I remember posting on my adventures ~ 1 year ago

[2Fass240us]

I think ecugrad nailed it. And I'm not just saying that because I happen to have a couple of 15/16" MC's sitting around. Def bought one not too long ago. PM me if you are interested. Hell, you'll net positive selling the 17/16" one and buying a 15/16".

As anothjer point of reference...I run hydraulic and brake force calculations frequently (in an Excel sheet) and sourced a 15/16" MC for a 6-piston Wilwood front with Z32 rear setup that I installed recently on a friend's S14. No lockup whatsoever. I can elaborate on the piston sizes, pad compounds, tires, etc. if you would like (and I can find the info).

[Umai Kakudo]

I have been having pretty bad issues with my Z32 brakes wanting to lock at the first sign of heavy braking.

. . . . .

Every time I go to brake heavily (at autocross and sometimes on the street) my front right wheel instantly wants to lock-up and it takes quite a bit more pedal modulation before the front left begins to lock.
. . . . . .

All the parts and pads advice is good to get the Z32 setup working properly.

Here are some other solutions in addition to that.

The front right wheel will lock first with stock brakes and good street tires.

Since you are competing also look into getting a good corner balance (and possible static weight redistribution) with your alignment.

This will even out the cross weights giving both front tires the same amount of grip so the fronts lock at the same time.

Also check to see if your compression damping is too stiff.

Don't discount technique. Threshold braking is very difficult and takes a lot of practice to master.

A swift but progressive ramp up to the lockup threshold helps transfer weight to the front end giving more available grip. If you can't change parts try and use you senses (sight, sound, kinetic) to become more aware of how the car is reacting to your inputs and experiment to find the best technique to get maximum deceleration without lockup.

If you don't have it a good race seat with harnesses (or CG lock for stock belts) frees you up from holding yourself in place so you can give better inputs into steering and braking.

[DuckyD]

I seem to brake OK when I start braking early, like at road course events. Autocross is another story, as our events are cramped and is very "point, shoot, brake, turn, repeat" type layouts. I do think technique does have alot to do with it.

As far as hardware goes, I am getting this feedback:

1) Grippier front tires means more brake force before lock-up.
2) Larger rear calipers means better overall stopping power before lock-up.
3) Smaller BMC will allow more more modulation.
4) Front right is lighter, so corner balancing may help put more weight (and force) over that wheel
5) Check dampening setting (which is near non-existant on Stances, btw).
6) OEM'ish pads might have less initial grip and not as likely to lock instantly.


Some good feedback. I think I might try the 15/16" BMC before the next event (Autocross Nov 8th and Time Attack Nov 15th).

[Matt93SE]

Edited in the order I consider most important, and included my notes. (YMMV)
I personally run Wilwood dynalites up front and Z32 rear. piston sizes and overall biasing is similar to the Z32 setups I've driven.


1) Check dampening setting (which is near non-existant on Stances, btw). (not adjustable, or just doesn't have much compression damping like Konis?) if possible check/adjust first since it's a free fix.
2) Front right is lighter, so corner balancing may help put more weight (and force) over that wheel this helps handling and braking, so it's on the to-do list as soon as you know you're done playing with alignment and tire sizes and etc
3) Larger rear calipers means better overall stopping power before lock-up. huge fronts and stock rears will leave you with a overly front-biased setup forever until you install an external prop valve or get bigger rear calipers
4) Smaller BMC will allow more more modulation.
5) OEM'ish pads might have less initial grip and not as likely to lock instantly. for Auto X, you don't need anything beefier than Hawk HPS. track pads FTL in this application because you don't build any heat in an autoX. You might even try an HPS front, HP+ rear setup to try to move some bite to the rear.
6) Grippier front tires means more brake force before lock-up. Last resort fix is going with funky tire selections, but you should be running something similar f/r anyway... Honestly I've had great luck with non-staggered tires on my car.

[Bumnah]

My approach to the brakes was to keep it OEM. I went with z32 front and rear calipers. Same brake pads front and rear. Same tires front and rear. And I run a 17/16" z32 bmc.

Since the proportioning valve is built into the bmc. I figured I would avoid odd braking issues that may pop up. Being a lighter car I figured I would only improve their performance in comparison to a z32.

Is any of my thinking flawed? I did a corner balance with an alignment, and I've had no weird issues. I may not be pushing it to the limit, so any shortcoming may still be hidden.

[Solo_S14]

Hey DuckyD, did you try the 15/16 BMC?
What were your initial feelings/results?

I've had the same problem with my Brembo GT fronts + Z32 rears + Z32 BMC.
I tried both the "stock" Brembo's and the Endless Blue track pads in the front, keeping the Endless Blue's in the rear both times.

I haven't tried a proportioning valve, and would like to try other options before resorting to that. Maybe my Endless Blue's would be more suited to one of the road racing guys on here, and I could get some Hawk pads for the rear......maybe this would help my setup.

Either way, if you've tried anything out, post an update, I'd be interested in hearing your opinions so far.

[ecugrad]

Dump the 17/16" MC!!! See post #8 in this thread and I have another thread on here about my misadventures with MC's.

Do you have ABS? I going back to stock brakes and have a 15/16" non ABS one for sale.

[Solo_S14]

I have ABS, but it's currently disabled.
How much are you selling your MC for?

[2Fass240us]

If you decide you want to keep ABS, you can use the S13 brake master. Otherwise, buy ecugrad's. He has twins and another one on the way. :)

[DuckyD]

Hey DuckyD, did you try the 15/16 BMC?
What were your initial feelings/results?

Either way, if you've tried anything out, post an update, I'd be interested in hearing your opinions so far.

I haven't done anything. Work has been busy and now I am going into Finals week. I do have a list (and a long one at that) of things that I am going to take care of over the ~3 week Winter Break.

I have not tried a 15/16 BMC, I did one autocross with the stock 7/8 (14/16) BMC and did not care for it. But the car had just undergone a lot of upgrades at once, and nothing was really sorted out. There too, I was expecting more braking force before lock-up and I was probably over-confident in my braking, was disappointed, and instanly jumped to the Z32 BMC.