As some of you guys know about my wilwood kit and the problems I've been having with a HUGE front brake bias problem, I finally got around to fixing it last weekend.
I did a few calculations and figured that with the larger pistons in the front calipers and the larger rotors, there is now over 3 times the braking torque on the front brakes as there was before the change. That obviously means my front brakes way overpower the rears.
Soooo, instead of the stock brake bias of about 70% ft, and 30% rr, I now had about 90% ft and 10% rear..

I knew this was a problem the whole time I had the kit on, as I was going through rotors on the front almost as fast as I was going through oil. I've about worn out my SECOND set of front rotors since this time last year. Not good at $300+ /set.

Anyway, so I set out my quest on increasing rear brake bias.. First step was to figure out what rotors would fit under my wheels. Even though these are 16" wheels, there is very little room, due to the 3-piece design on the rims. the bolts that hold everything together are right where I need room for a caliper. DOH!

I did some searching around in hundreds of websites and many brake parts catalogs and blah blah blah.
Seemed the best solution I could have came straight from Nissan already- on the first Gen (84-89) 300ZX. lucky me!
The rotor thickness and offset were identical to Maxima rotors, except they were an inch larger in diameter. Problem solved.

Now to get them mounted. As you can see, the mounting brackets on my car already had two sets of holes. This was from when I pioneered the rear disc conversion on my old GXE. When I totalled it, I simply swapped the rear suspension over to this car to save from having to tear down both sets of springs&struts to swap the Tokico/Eibach combo. Reason there's two sets of holes is that when I purchased the parts, the junkyard gave me calipers off of a different year Maxima than I got the rear struts and brackets. The struts and brackets were off of a 94SE, and the calipers were from a pre-90 SE model. They changed some dimensions of the caliper on the 91+ models to make the bolts easier to reach on the calipers for maintenance. (if any of you pre-90 guys have removed a rear caliper, you know what I'm talking about).
Sooo, when I bolted up the original rear disc conversion system on the old max, the calipers stuck way out past the rotors because of the design change. My fix then was simply to drill two new holes in the bracket so that I can get the car back together and have rear brakes without having to order MORE parts and wait another 2-3 weeks to finish. blah blah blah

So, for the last YEAR, I've been dreading having to repeat the bracket fittment hassle I'd had on the rear disc conversion.. I finally got my garage cleaned out enough to get to my drill press useable again, so I figured I'd start and see where I had to go. I had some spare pieces of metal and the tools to make a copy of the bracket available, and the time to do it. blah blha lbah.
So I pull everything apart and THEN remember I had to drill another set of holes in the bracket. *Hmmmmm... wonder if that will fit?*
So I stick the new rotors on and bolt the caliper to the old holes in the bracket, and VOILA! the pads only overhang about 1mm at the most, which is less than 1% of the pad area. Good enough for me!

So that's pretty much it. rear disc upgrade on my car in less than 2 hours!

As for driving impressions, there was an IMMEDIATE difference in braking. the car feels much more balanced now, and I can brake much later going into corners and stuff.. It's almost impossible to lock the brakes up, but if I really try it's doable. by that time, you're about to bend the steering wheel over from pushing so hard on it. 100-0 braking distance has significantly decreased... When I stomp on the brakes, the car almost immediately comes to a halt with no drifting or front-end lockup that I had before. Brakes are simply amazing now.
It's actually fun driving the car again!

A 4-5pt harness will be my next mod to the car, as soon as I finish putting the Z seats back in. Hmmmm, I think I may tackle that today even! ;-)

I'll quit rambling now and show you kids the pics.

http://www.ee.utulsa.edu/~mblehm/pic...akes/rear1.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear2.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear3.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear4.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear5.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear6.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear7.jpg
http://www.ee.utulsa.edu/~mblehm/pic...akes/rear8.jpg

 

niceee

 

nice job Matt, I need to upgrade my brakes as well

 

wow looks cool, and it's really great that you've balanced out the brakes! I just want slotted rears to match my fronts.

 

Stopping.... who cares about stopping

Seriously though great work, I've always thought about what happens to the rears if you get a humongous front. This isnt like a sport bike where 90%-100% of the braking is done by the front anyway.

...and I have to commend you for posting results AFTER it was done, and not BEFORE.

 

Good job Matt... now if it could work for the 4th Gen... alas... I'm getting tired of waiting for someone to make a kit...

 

Bring your car to Tulsa some weekend and I'll play with it for a day or so. ;-)

According to DBA's database,
The 4th gen rear rotors are 278mm, 3rd gen are 258mm, and the Z31 are 290mm.

With that information, the 4th gen really won't benefit much from Z31 rotors in the back, but every bit will help. Probably the best thing to do would be to remove the stock rear brake bias equipment (which I don't know where or how), and then install an aftermarket brake bias adjuster on the back. The rear rotors really don't do that much work, so I don't see it being a problem giving the rear brakes a bit more work to do.
Might be something to look at. Spend an afternoon with the FSM and do some studying.. might find a easier/cheaper way to fix the bias problems than I did.

 

Wow thats really ingenuitive, nice work.

 

if you 4th gen guys are interested. might want to check out 02 ALtima rear brakes. i seem to rmemeber somewhere that they were 11." rear rotors. i could be wrong tho.

 

Matt, so when a car gets the big brake kit in the front of the car but not the back the front automatically gets more brake bias? but if you add the big brake kit to the rear of the car it evens it out? Im confused.

 

The bias is preset by the manufacturer... most are 'properly' balanced while some are not so. ABS maximizes braking (and minimizes bad design) by monitoring each wheel.

The 'bias' of adding aftermarket brakes depend on 2 things... the diameter of the rotor (leverage arm) and the surface area of the caliper pistons on one side of the caliper. The stock bias on the 4th Gen seems rear heavy seeing that adding my Superlites on 12.2" rotors is pretty well balanced (I don't have ABS).

Matt, don't tempt me or I might show up in Tulsa one of these weekends

I may just order the 12" Wilwood solid rotors and do some measuring with my existing front hats.

 

12" Wilwood solid rotors?

which ones are these? I haven't been able to find hats anywhere that fit our cars, other than the kits out there already. the offset is tiny compared to anything listed on wilwood/coleman/AP/Brembo's websites..
I ended up buying a set of hats from Fastbrakes, and will order some Coleman discs when these skyline rotors finally die... but if I can find another place that sells the hats- or large rotors that are cheaper than skyline rotors, then I can work on some other brake kits for other people..

 

I'm hazarding a guess here, but with 4th gens it's a different ball game in the braking department since they gained some weight. From my experience with driving both, there is more brake bias on the backs than the 3rd gens had due to Nissan's unwillingness to go with a bigger stock wheel and/or better front calipers. I would guesstimate the bias on 4th gens to be 65/35 or so, with 3rd gens being in the 75/25 range.....so there just may be more benefit to going with larger rotors on the 4th gens than it appears.

Nice job, Matt. Time for another visit.

 

Yup.. as I said earlier, the 4th gen rotors are 20mm larger than 3rd gen, with the same calipers and pads..
the front brakes are exactly the same, so just by looking at those two things (ignoring pressure from the master cylinder), the 4th gens have more rear brake bias..

This is probably why you don't see as many complaints on the big brakes kits on 4th gens as you do with 3rd.

 

anyone know how big the rear rotors are on the 5th gens? vq30 and vq35? i am curious.

 

http://www.dba.com.au/catalogue/pdf/nissan.pdf

According to that, they're the same as 4th gens.. but they also say the front rotors are the same as as 4th gens, which I know that's not the case.

Could be some of the aussie-spec stuff coming into play on that one, so I wouldn't go too far in trusting those data sheets.