Disclaimer: I do not consider myself an expert at braking systems. I am no automotive engineer. I base my conclusions on real-world
experiences and those experience shared with me by others whose assessments have learned to be trustworthy and credible. What you are about to read
is just some numbers, data, and observations I came across while "researching" what I already knew to be true based on my experiences and those shared
with me by others. In other words, this isn't gospel, just one Z'ers informal look at some of the Z32 BBK's. A "pseudo-intellectual" look, for the
results-minded. There many other kits available than what is mentioned here and anyone interested in those kits should obviously gather their own facts
about them. It is not my intention to suggest that Stoptech or Wilwood are the final word in BBKs for Z's, street-driven or otherwise.
_________________________________________________________________________________________________________________________________While doing 2 minutes worth of "research" today, I discovered a
BRAKE BIAS CALCULATOR
allowing anyone to get a look at how a particular brake kit can affect braking bias when looking to boost overall braking performance via modifying brake
systems. 10 more minutes of "research" and a 5-minute phone call later and I had all the data I needed to look at a few different setups.
-OEM specs can be found on page BR-46 in the Factory Service Manual
-Wilwood offers oodles of data on their site, but you must call for actual "radial height" of the pads
-Stoptech's site listed their pad dimensions, but I had to rely on hearsay from a "credible" source for the piston size. I ran the #'s for 4 different possible kit configurations vs stock. Two are from well-established Wilwood kits; the RMS Horsepower kit and the Arizona Z Car
kit. I have the latter on my Z and have tracked it a handful of times. I then looked at a couple of Stoptech configurations both using their 4-piston ST40
calipers; one with 355mm rotors, the other with the more common 332mm rotors. The results (as a % of front braking bias)
OEM---0.667
Stoptech ST40 w/332mm rotors---0.682
Stoptech ST40 w/355mm rotors---0.700
Wilwood (RMS Horsepower specs)---0.708
Wilwood (AZ Z Car kit specs)---0.717 With "optimal braking" being front bias approaching the point where the rear brakes are just shy of locking up or the car becomes unstable, every car will
see different bias %'s for optimal braking depending on wheelbase, weight distribution, front vs rear tire grip, etc... With so many variables, the seeming
common sense way to "get there" is to have an adjustable proportioning valve and simply "dial it in" on-track. So all things being equal, with the AZZC BBK, you are looking at an extra 5% of front bias, with the 332mm Stoptech BBK you will see an additional
1.5%. Obviously running different pads front and rear will have some effect on all of these configurations in either direction, whether it is perceptible
while driving is something else. I can testify that pedal feel and overheating have been of no concern on my Z with the AZZC, nor is quality of the parts.
Both use curved-vane rotors, though Wilwood doesnt have a fancy name for theirs. Stoptech has a patented rotor-hat design for airflow over the
outer face of their rotors and a caliper "bridge" design for caliper stiffness. I personally have never heard of any Wilwood users having overheating issues or
complaining of lack of "stiffness". This is likely a bigger deal for competition grade cars, and "placebo" for the rest of us if I had to guess, great for
marketing though. Stoptech uses forged aluminum calipers, Wilwood uses billet aluminum or you can buy forged aluminum. The pros & cons of either are not
something I am familiar with, sorry. I imagine both must be lighter than OEM in the unsprung weight category. I didn't weigh my Wilwood kit during
installation, but I held the caliper/rotor in one hand and the OEM's in the other and they were appreciably lighter. Wilwood claims improved performance on
their billet Superlite 6's due to the directional design of their calipers with the larger piston trailing two smaller ones. Again great for marketing and they
have data to support it, but I think most practical-minded recreational track-goers will tell you these are irrelevant niceties. Ultimately, what it all boils down to is cost-effectiveness for the non-competition-grade street-car. There are plenty of Z'ers here who track with both
Stoptech 332mm and Wilwood 332mm brakes and can tell you that both are more than up to the task. It is up to you whether you feel there is an actual
need to spend $500-$1800 extra for differences in styling and "gee-whiz" design features. You can spend $3400 for the 355mm Stoptechs, but the data
does not support any "balance" advantage over the $2k Wilwood kit that will still fit inside stock wheels, PLUS you will stray further away
from the OEM braking bias than the 332mm Stoptech kit which also costs $1400 less. Or you can spend $1500 for the AZZC and if the additional front bias negatively impacts your Z, then you can add the adjustable proportioning valve ($65)
to the system and dial it in for braking balance exceeding any of the others and tailored exactly for your Z. I chose the least expensive route, after
initially thinking I was going to buy the Stoptech 332mm kit and asking around and reading opinions of other Z'ers who frequent track days. I do not feel
there is a need to "tweak" the brakes for my non-competitive purposes on my 2seater to get to the 3.5% less front bias of the Stoptech 332mm kit. Should
I change my mind, I can get there with $65 as opposed to the extra $500, and I will have a fully adjustable kit as opposed to a fixed one. My $0.02 _________________________________________________________________________________________________________________________________ Input data I used for the calculator, for error catching purposes:
Pedal pressure--60lbs
Master Cylinder diameter--1"
------------------------------------------------------- Front piston diameter--
ST40= 1.5"
OEM= 1.6"
Wilwood SL6= 1.31" * Total piston area--
ST40= 3.534
OEM= 4.021
Wilwood SL6= 4.043
Front pad cF--0.6
Front rotor diameter--
ST40= 14" / 13"
OEM= 11"
Wilwood= 13" / 12.5" Front pad radial height--
ST40= 2"
OEM= 1.97
WilwoodSL6= 1.625" Front rotor torque(in/lb)--
ST= 77760(14" rotor) 71280(13" rotor)
OEM= 66576
Wilwood= 84329(13" rotor) 80622(12.5" rotor) ----------------------------------------------------------- Rear piston diameter--1.5"
Rear piston area--1.767" Rear pad cF--0.6 Rear rotor diameter--11.7"
Rear pad radial height--1.43" Rear rotor torque(in/lb)--33274.8 ------------------------------------------------------------ Front bias--
ST40= 0.700(14" rotor) 0.682(13" rotor)
OEM= 0.667
Wilwood= 0.717(AZZC) 0.708(RMS)
*--Wilwood total piston area @ 4.04" and then averaged between the 3 pistons
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