So I need new front brakes anyway, and I currently have J30 front brakes on the car (previous owner installed them). The passenger's side caliper is a little stuck, the pads are shot, and the pass. side rotor may even be a bit warped. Since I need to replace all but one caliper anyway, I'm considering returning the front brakes to stock. My main reason is clearance. I'm completely sick of the control arm grinding the rotor when I have the wheels turned to full lock, it's annoying. I've done everything in my power to remedy that problem and cannot find a solution. Also, buying all new factory stuff is much cheaper than buying new J30 parts, having a new set of rotors milled down, etc. etc. So I have a couple of questions:

1. Am I correct in believing that the factory front brakes have more clearance between the rotor and the suspension?

2. Do I need anything to convert back besides new factory calipers, rotors, and pads?

 

Pics of grinding?

I have the 300zx with 12.6in rotors and no grinding.

You have J30 calipers and modded J30 rotors or max unmodded rotors? Did it use the J30 tq member or the max tq member?

 

Actually, I guess I don't know. I honestly don't know a whole lot about the swap since I didn't do it myself. What's the most common setup? I believe it uses modified J30 rotors. I was under the impression that that way was the only way to do it.

The grinding is only with the wheel turned one direction (right), and I thought I had it figured out but apparently I don't. I thought maybe it was because I didn't shave enough off the new control arm when I put one in a few months ago (part of an accident, see my thread) and what I saw tonight backs up that theory. Only the backside of the end of the control arm has bare metal (meaning it scraped the rotor) which matches up perfectly with the grinding only occurring when I turn right. BUT, I checked the clearance with the wheel turned full lock to both sides and there's room to spare...and the grinding is still happening. Could it be that only when the car is on the ground under full weight that the control arm is touching? It would be at different angle than it is up on a lift, would it not? I might just need to shave a tiny bit more off.

Regardless, if and when I go to get a new car I will most likely trade it in and I would feel really bad handing over a car without factory front brakes. I also don't NEED the J30 front brakes because I rarely drive spiritedly in this car anymore and I am usually downshifting to scrub speed anyway. I feel like I wouldn't even notice a difference going from worn-out J30 brakes to fresh A32 brakes with some really good pads.

EDIT: Is there any tips you can offer me for identifying my specific setup? Maybe some measurements of rotor sizes or something?

 

a picture

 

Alright, I'll see what I can do. I wish I had taken one while I had the wheel off last night inspecting the car.

 

The Z32/J30 rotor is MUCH thicker than the A32 rotor. That should tell us.

And if you are selling the car to anyone, then do convert back to the stock setup.

www.rockauto.com has great deals and google their 5% off coupon.

Also, advanced auto has some coupons too:
http://www.couponcabin.com/coupons/advance-auto-parts/

 

Are the thicknesses listed online somewhere? I could take some measurements tonight.

 

28mm is the Z/J rotor

Ours are IIRC, 26mm. But less than 28mm either way.

 

^^^ no

4th gen rotors are 22mm thick, 2000-2001 rotors are 26mm thick, J30s are 28mm thick, 300zx are 30mm thick except for the rare 26mm thick rotor that was only used in one or two model years, on the non turbo 300zx.

all thicknesses available in FSMs, or alternatively on autozone's website.

 

Whoops, thanks for the corrections

 

anyways. i had j30 rotors (28mm) and j30 calipers using 4th gen torque members on my 3.5 car. nothing needs to be done to the rotor, no milling or anything. the pads needed to be sanded down because when coupled with a 28mm thick rotor, brand new pads are too thick to fit in the caliper. needed to sand about 1mm off, which was actually a real pain in the butt. took a few hours to get it right, and was messy. the rotor does not rub the LCA on my car. also had to grind some off the mounting surface of the maxima torque member, and also grind away some of the "high points" inside the maxima torque member, to open it up enough to fit a 28mm rotor inside it. using a 30mm rotor would be really, really hard with a maxima torque member, and I'd be really hesitant to take that much material away from the maxima torque member (basically you'd need another 2mm taken away. i think that's getting to the point of causing strength issues. you'd probably be cutting down 20% of the thickness of it.)

I never tried fitting a j30 torque member, not sure how they differ from maxima torque members. using j30 torque member might be the way to go, since it would already be wide enough to fit 28mm rotors, it might be plug and play, or at the very least require less grinding.

edited because i typed something incorrectly, and all the brake changes i've made are starting to run together in my head:

I have 26mm 5th gen rotors on my 3.5 car now. I had to add a washer between the torque member and the steering knuckle to space it back out. this was at least in part - or maybe entirely - because of the grinding i had previously done on these torque members to get the 28mm rotors to fit correctly (I had to take material away for the 28mm upgrade, and basically had to "add it back" in the form of washer for the 26mm upgrade, because the offsets of the 26mm and 28mm rotors are different). the 22, 26, 28, and 30mm rotors all have different offsets. one could probably calculate how much adjustment, if any, is required to make the 26mm rotor fit properly without rubbing on the 4th gen (unaltered) torque member. I will likely test this some time, as I have 100% stock style brakes on one of my 4th gens, and these modified ones on my other one. and if the 26mm rotor can be easily put on the 4th gen using a 4th gen torque member, it would be a nice, cheap, upgrade, being as the 26mm rotors are almost 20% thicker than factory rotors.

 

So what setup is the most commonly done then? J30 calipers, rotors, and pads on an A32 torque member? I'll be taking pictures and measurements here in about an hour.

 

Here are some pictures I snapped this evening:






I have a few other weird close-up shots if you think they'll be helpful. Looks to me like 28mm thick.

EDIT: If I do indeed convert back to factory, can I use '00-'01 rotors in the place of A32 rotors? Sorry, I'm not well educated when it comes to brake setups anymore I'm also having second thoughts about converting it back after seeing some of the deals RockAuto has on J30 calipers right now. I could just replace the sticking one (pass. side) and buy new rotors and pads. I'd be saving like $50 or $60, too. Now are you saying I wouldn't need to modify the rotors? Also, if you had to take 1mm off the pads to fit the 28mm rotor, couldn't you just use a 26mm rotor instead and not remove material from the pads?

 

My instinct is that you could use the 26mm rotor instead, but I haven't crunched the numbers (the offset numbers) nor test fit it to actually determine whether or not it would work without any modification. I used 28mm rotors because I wanted as much rotor mass as possible for road course use. I did not know I would have to shave the pads until I was trying to fit the caliper and pads on the car (after installing the rotor and doing all the grinding on the torque member that I did). I was (as far as i know) pioneering this setup so I didn't have any other info to follow, just trial and error and modification until it worked.

If you indeed have 28mm rotors I don't know why you're rubbing, mine don't. Might have to do with ride height differences, as the control arm would be at a different angle with different ride heights. I have never measured how much clearance I have with 28mm rotors, no idea how close it is. But I've never heard anything rubbing nor seen any evidence of it.

One of these days I will take both of my cars apart and try to see what it takes to make the 26mm rotors fit on an otherwise completely stock setup, and a J30 setup without grinding on the torque member.

BTW what you have looks like either Q45 or J30 torque members to me, maxima 4th gen torque members aren't that beefy looking, and I assume 5th gen torque members aren't either, though I don't know for sure.

Buy some 2000-2001 26mm rotors and see if they go right on there without needing to do any grinding or anything. if not, return them. or try the 1990 300zx NA 26mm rotors (they are different offset, post to follow).

 

Here are the rotor dimensions. Notice the different offsets of the rotors. Images credit to auto zone. don't sue me please lol

J30 and 1st gen Q45 28mm rotor
25.8mm offset distance from rotor hat surface to outside surface of rotor disk




300zx turbo and late 300zx non turbo 30mm rotor
16mm offset distance from rotor hat surface to outside surface of rotor disk




95-99 maxima 22mm rotor
27.5mm offset distance from rotor hat surface to outside surface of rotor disk




2000-2001 maxima 26mm rotor
27.6mm offset distance from rotor hat surface to outside surface of rotor disk




early 300zx NON turbo 26mm rotor
24.3mm offset distance from rotor hat surface to outside surface of rotor disk

 

From what I'm calculating, I think the best bet for a plug and play thicker rotor solution is probably 26mm 300zx non turbo rotors. I think the 26mm maxima rotors might stick too far "in towards the car" and that the "back" of the rotor might rub against the torque member without some grinding modification done. On the other hand, if the 26mm 300zx rotors did NOT work without modification, it would be much easier to space the torque member back in towards the car with a washer and use the 26mm maxima rotors, than it would be to grind on the torque member a bunch, to space it out away from the car to clear the 26mm 300zx rotor.

I have J30, 22mm maxima, 26mm maxima, and 30mm 300zx rotors in my possession. all I would need would be a 26mm 300zx rotor, and maybe pick up a couple torque members (2000-2001 maxima, and J30/Q45) from a junk yard, and I could test every conceivable combo you can think of in a single afternoon and figure out what works and what doesn't (as far as plug and play goes).

 

Well if I'm going for the least amount of work, would you recommend I just go with another pair of 28mm rotors? I found the area where the control arm is rubbing the rotor and I think it's only touching when the car is sitting on the ground, otherwise the angle is different and it has enough clearance. I'm pretty sure it doesn't rub all the time, just when I turn right. I can tell because there's a little spot of bare metal on the control arm where you can tell it's been rubbing something, and no bare metal spots anywhere else. I already ground some of the control arm off when I put the new one on because I knew it would need modified a little to clear, but it looks like the area where it's touching is where I ground off the least amount of material.

I should have taken pictures of the control arm last night. D'oh...

 

Bump for potential additional input.