spacers, under the hat on rear disk brakes?

[Guest probablecauZ]

I've read a ton of threads on rear disk brakes, but i would like to try to use the 300zx(87) rear vented rotors! If I were to install long ARP wheel studs is there any reason why I couldn't use a spacer under the rotor hat, to allow a little extra room for a bolt on caliper bracket? Maybe even enough room to allow a flat bracket? From what I have read it seems that the Z31 5 lug hubs/ redrilled 260Z rear stub axles is the way to go, but the rear rims would have a much smaller offset (closer to center of the rim) than the fronts. So if i plan on running 17x7's or whatever, the rears would need spacers any way if I wanted identical offsets for all of my wheels, so i could rotate? So if I need a spacer anyway could it be under the rotor hat, or split the difference and have a spacer under the hat against the hub for caliper bracket clearence and whatever additional thickness I would need between the rotor hat and wheel? Also is there anything i should know about 300ZX rear calipers, or alternatives, with parking brakes, for the vented rear rotor.

Thanks, Alan.

[blueovalz]

Further analysis may prove me wrong, but I cannot see any difference between a spacer inside the rotor verses a spacer outside the rotor. It would seem the same shear forces are involved (with longer than normal studs) in either set-up, whether it be between the wheel and the rotor, or between the rotor and the axle flange. I personally don't like spacers (even though I recently had some machined for me) that only use a "pass-through" stud, but I would definitely stay away from multiple spacers (ones on both sides of the rotor), especially, as I said before, if you're only using a single long stud passing through all these parts. I've no emperical evidence to prove this, but smooth surfaces stacked up together would scare me in that I would believe any slipping between parts (unless there were some really close tolerances in the stud holes preventing any slipping) would really stretch the studs out, perhaps beyond their failure limit. I guess the reason I fear this is that one day I removed some spacers on a car many years ago, and saw on the aluminum surface signs that there was movement between the rotor and the spacer, even though the wheels were bolted on tightly (both surfaces were very smooth). Perhaps indexing pins would make me feel better about all of this.

Anyway, on the 1/2" spacers I had machined, the stud holes were so snug on the studs that I had to tap them on with a hammer.

[Guest probablecauZ]

Thanks for the insight, I want to get a bunch of opinions on this as I don't want to put too much faith in an idea of mine with out any other suggestions. When it comes to brakes and suspension, IMO, the more parts the higher probablity for faliure. I know a bunch of people run spacers or adapters and have had good experiences with them, and I know a few that have not. I have a 260Z that will be recieving a mild Chevy 383 so torque will be pretty good. I want disc brakes all around and the 5X4.5 bolt cicle for wheel options!

I might get different width wheels front and back so the spacer may not be nessecary, but if it is... and it being under the hat of the rotor isn't a problem, then i can have huge vented discs in the back. I follow what your saying about runing 2 spacers, one on either side of the rotor, sounds a little worse to me aswell. But does any body know if a spacer under the hat has ever been done before, just a big

"what if?"

[datsunlover]

Well, if I'm not mistaken, that's exactly what the toyota caliper/300zx front brake swap requires; Spacers behind the front rotor. I can't see why it would not work for the rear. I'm running spacers on the front for my rims (FWD offset) that I made at work. 1" thick and 6" dia iirc, and I made them so I had to tap them on with a hammer. They are aluminum yes, but they are on the outside of the rotor. Been on there for 3 months of hard driving and I havn't had problems. For the rear, behind the rotor, I would recoment steel however.

[Here comes trouble]

I am surprised so many members missed this recent hybrid z swap when a stock set of Maxima offset caliper brackets went for $336.13 with a couple of Earl's ss lines on eBay (no bull ****). I am going for this member's full maxima swap and should come under $100.00 with all Maxima parts including machining with the ss lines costing about as much as the complete conversion http://forums.hybridz.org/showthread.php?t=102340

[Guest probablecauZ]

Those are the same brackets I have! I went to pick-n-pull and grabed 2 sets of those, 2 '87 300ZX calipers for cores, and 2 vented '87 300ZX rotors that had almost no wear, just surface rust. I am thinking that I'll have the rotors turned just to get the rust off. Once I have the stub axle drilled for the 5 lug, and new bearing I'll mock it up. I'll cut one set of brackets to mount on the housing and weld the ears off of the other set over laping to give me ~.5 inch offset (thickness of the bracket). Then see what I will need as a spacer under the rotor hat to center the rotor in the caliper. I'll keep posting on my progress, if there is any and take pictures aswell. I really want those big vented rotors in back!

[Cody 82 ZXT]

Those are the same brackets I have! I went to pick-n-pull and grabed 2 sets of those, 2 '87 300ZX calipers for cores, and 2 vented '87 300ZX rotors that had almost no wear, just surface rust. I am thinking that I'll have the rotors turned just to get the rust off. Once I have the stub axle drilled for the 5 lug, and new bearing I'll mock it up. I'll cut one set of brackets to mount on the housing and weld the ears off of the other set over laping to give me ~.5 inch offset (thickness of the bracket). Then see what I will need as a spacer under the rotor hat to center the rotor in the caliper. I'll keep posting on my progress, if there is any and take pictures aswell. I really want those big vented rotors in back!

 

 

So what are the specs of those rotors?

[zcarnut]

A problem with trying to use the 1987 Z31 rear caliper on an early Z car is the parking brake operation. On a Z31 the direction of pull of the parking brake lever on the caliper is to the front of the car. When the right and left side calipers are reversed (i.e., left caliper is used on the right side and vice versa) so they can be used on a 1970-78 Z car, the direction of pull of the parking brake lever on the caliper is now to the rear of the car.

 

This is difficult to make operational. The [custom] parking brake cables have to be routed so they pass under the fuel tank and curve back to the caliper avoiding the strut tubes and the exhaust pipes. I spent some time trying to make this work but I eventually gave up.

 

I would recommend using another rear caliper that can handle a vented rotor. However, there not a lot of junkyard choices. The late 1980's Mazda RX7 had vented rear discs and rear caliper has the parking brake lever angled in a more usable direction. It is also made of lightweight aluminum. The bolt spacing of this caliper is much wider than the Nissan units so you would have to fabricate a bracket to position these calipers. The Nissan Z32 and the Toyota Supra also had vented rear discs, but used the “drum in hat†concept for the parking brake, which is a much better way to handle the parking brake but would require a lot of modification to the early Z car rear strut.

 

There are a more choices when it comes to finding a suitable vented rear rotor. Some front rotors from other Nissans, Toyotas and Subarus will fit. There is no reason to go to 5-lugs (unless you just want to) just to use a rear vented rotor. The front rotor from a 1985-88 Maxima (which is what I used in my experiments) will fit the rear hub of the early Z car with just some minor grinding.

[Guest probablecauZ]

Thanks for all the input! Since it is questionable I will most likely not use a spacer under the hat of the rotor. So I guess that means I'll be doing a weld on bracket. The rotor is ~11 in. dia, total height ~2.25 in., rotor thickness ~.75 in., with the 5X4.5 bolt circle and the center pilot hole slips right over the pilot on the stub axle. I want to keep the rotors because they're in good shape for $8 at the JY, and the big hat height(~1.5 in.) allows for caliper clearence with out worrying about clearence on the wheels. Maybe the calipers I got are different but I'm pretty sure they were off of a '87 300ZX, and it looks like the parking brake cable could come up from the bottom of the housing and might not need to be routed from the back of the car, i.e. fueltank, exhaust etc... This is of course with the calipers flipped so the the bleeder valve it on the top. Thanks again for the suggestions!

[Guest probablecauZ]

My bad, I had the Struts backwards, in my head (much like a lot of other things). Now I see that the caliper probably will not work, doh! Good thing I got the return package at the JY for the Calipers and Rotors. GOOD CALL ZCARNUT.

[Here comes trouble]

Z Car Nut, Cody and DAW shot the full Maxima rear brake package down for lack of emergency brake compatiability..............Not much can get by these guys.