Z-to-ZX Brake Update
Front Brakes The non-ventilated Z rotors did not do much for my "racing" appetite, and in looking for bigger rotors and calipers, I considered using the 280ZX brake assembly, but quickly realized that even though the 280ZX rotors were thicker and ventilated, they also were of considerably smaller diameter (10" vs. 10.7") than the original 240Z brakes! Thus I turned to the regular 300ZX rotors because these were ventilated rotors that were a good bit thicker (22mm vs.18mm) and of a larger diameter (10.8" and actually only .1" larger than the Z rotors) than the 280ZX rotors. I should mention here also that all the Z/ZX 4 bolt hubs will allow interchange of any rotor onto any hub as far as being able to be physically bolted together. In other words, any Z or ZX 4 bolt hub will accept any other Z or ZX brake rotor as far as physically bolting them together, and disregarding any differences in rotor offset which will become very important as you will see! Also any Z/ZX 4 bolt hub will also fit onto the Z spindle too, with the only difference being a very slight displacement of inside seal (the wheel bearings are the same). I did not use the 300ZX calipers though. The reason I did not follow suit with 300ZX calipers was because these calipers were wider, heavier, and had a different bolt spacing than did the 280ZX / Z calipers, even though the piston and pad area on these calipers was no bigger than the piston and pad area on the 280ZX caliper. Thus I opted for the 280ZX calipers, because the brake pad area and piston area would be the same as the 300ZX calipers, but the installation requirements would be easier and there would be less unsprung weight involved too. Many folks have questioned my choice in using the floating calipers vs. the Toyota 4 piston calipers. My answer is as follows; To use the older Toyota calipers on an unventilated stock Z rotor, in my opinion, would have been a waste of time, considering the stock rotors were already showing the signs of overheating, and this mod would probably make it worse. To use the newer Toyota calipers on the 300ZX rotors would have caused wheel/caliper interference due to the pistons on the wheel side of the Toyota rotor are thicker than this same side for the ZX floating calipers. To fix this I would have to use wheel spacers (about 1"), and in some sanctioning bodies this is illegal.
Front Street Version To start with, I drilled the existing threaded caliper mounting holes on the Z strut with a 15/32" (12mm) drill, thus eliminating the threads. This was done because the 280ZX caliper mounting holes on the calipers themselves are threaded, while the Z caliper mounting holes are unthreaded. In other words, the Z and the ZX calipers mount in opposite ways from each other in reference to what the bolt passes through and what the bolt threads into. The 280ZX calipers ( not the 300ZX ) have the same spacing on these bolt holes as do the Z calipers, so that with the old threads removed with the correct size bit, the ZX calipers can now be bolted into place by now pushing the 12mm bolts through the strut, and screwing them into the ZX calipers ( exactly opposite of the Z installation). One note to mention here is that some sort of spacing will be needed to center the caliper over this ZX rotor on the Z strut, because the backspacing, or offset, between these two rotors will differ. On my particular arrangement, I found that a thick .160" washer, placed between the caliper and the strut, worked quite well. It is very important to mention here, that the Z, as well as the ZX hub/rotor assemblies used varying combinations of offsets to reach the same "total combined thickness" or "offset" of the assembled parts. I have seen hub flange thicknesses (the wheel mounting flange where the wheel studs are pressed in, and the brake rotor fits against the inside) vary from 17mm to 25mm for the 240Z and 280Z hubs respectively, and 22mm for the ZX hubs, and I feel there may be more I haven't seen yet. Thus, it is very important to check your pieces very carefully, prior to any machining to find what will be required to make parts fit correctly. In my case, I used '71 hubs that had a 17mm thick flange. They are easily distinguishable from the later years by the concave half-moon shaped casting of the wheel mounting flange material between the wheel studs on the outer circumference. With the thicker, later model hubs, material would have to be removed from the rotor mounting surface on a lathe to make it work. This is because the thicker flange would "push" the rotor further toward the strut, thus creating "negative" spacing for the caliper. Then instead of adding a spacer between the strut and the caliper, you would instead have to remove material from one or both. With this the mounting of the calipers is now complete. The next step was to modify the 300ZX rotors so that they would fit correctly underneath or "in" the calipers. Through trial and error, I took them to a brake shop and had the rotor outside diameter reduced by approximately .250". This was done so that the rotor would clear the caliper in the current location as noted above, and still have about .020" of rotor extend beyond the brake pads.
Front Race Version This version is quite a bit more work than for the street version, and considering the only gain is diameter larger rotor size. I personally don't feel it is worth the extra work. Note: I have replaced the wheel studs pressed into the hubs with some aftermarket Ford NF studs. I pressed the Datsun studs out, drilled the existing holes out to 19/32" holes, and then pressed the new Ford studs in.
Rear brakes
Rear Street Version To mount the caliper chosen necessitated the fabrication of a caliper mounting bracket using plate steel. This mounting bracket bolted onto 3 of the 4 bolt holes in the strut were the old drum brake backing plate used to bolt on at. The bracket consists of steel plate cut to a half moon shape, then drilled to match the backing plate pattern (strut pattern). Then another plate with the caliper bolt pattern drilled into it was welded to the previously mentioned plate at an offset to center the caliper over the rotor correctly. After making this bracket I assembled the rear brake assembly by putting the rotor onto the axle flange ( the rear rotor slips over the axle flange just like it did on the ZX cars) and then bolted on the 280ZX Turbo rear caliper to the fabricated bracket. I then removed the insides of the brake proportioning valve to regain a balanced brake system again. The emergency brake cable was moved slightly by moving the supports, for the emergency brake cable, overhanging the half-shafts so that it would reach the calipers, and at the same time not rub the half-shaft boots. When I first replaced the front only Z brakes with the ZX brakes, the car was almost dangerous to drive in the rain due to the increased performance of the front brakes verses the stock rear brakes. I nearly always, in a hard stop situation would lock up the front brakes very easily. This was incentive enough to balance the braking ability of the car by improving the rear brake performance too, and at the same time, making maintenance much easier due to the disc brakes. Note: Below in the rear race version, a Nissan part, unmodified, bolted to the original backing plate holes may hold an acceptable caliper in the correct position for this non-ventilated rotor, but I'll leave that investigation up to you, but it may be worth you time to look into it.
Rear Race Version To begin with, I wanted to basically have the same brake system on the rear as I did on the front. So my quest started with trying to find a rotor to fit under the 280ZX front style caliper. Luck was with me in my quest for parts on this job, because just by luck I happened across a rotor that was the exact same thickness and outside diameter as the front 300ZX rotors, but with a different center portion, It is an '85 front rotor from a Maxima. The center section was designed to fit the "driving" portion of the front wheel drive Maximas. What better choice than to put it on the "driving" portion of a rear wheel drive car. After grinding about 1/8" off the outer diameter of the axle flange, so that it would fit inside this rotor, I simply fit the rotor over the existing wheel studs and axle flange, almost as if it where made to fit. It fit exactly just as the stock ZX rear rotors would normally fit. When it came to attaching the 280ZX front calipers to the rear strut luck was again with me when I came across a caliper mounting bracket used in the Maxima ( part # 44155-04S10 for the '82-'84 model ). This bracket will bolt into the original location and holes where the backing plate for the old drums used to go. But before you do this you must grind away some minor amount of material at different locations so that the rotor will clear it and so that the calipers will be spaced correctly over the rotor. Also, new holes must be drilled to match the 280ZX front calipers mounting holes. This may sound like a lot of work, but its a well made piece, and it easier to do this than to make a piece out of plate steel, because of the hard and very tight clearances required to fit caliper over rotor. Also, you may be able to use the corresponding brake rotor/caliper assembly that Nissan used with this bracket, and get away with a pure "bolt-on" modification (This would work very well for the above "street version" I feel). Anyway, I now have a means of bolting on a 280ZX fron caliper onto the rear strut of a Z car. The brake hose off the calipers was then routed into the small holds behind each seat in the rear deck, and then were attached to regular steel brake lines that ran inside the car to the firewall, and into the master cylinder (to ease any maintenance of brake lines and for installation of adjustable proportioning valve). Remember, no emergency brake!! But who needs one on a race car. The balancing of the brakes was achieved with the proportioning valve, which I had hoped would not be necessary, but was. Note: Since writing the above modifications to the racing rear brakes, I found that certain race set-ups required the brake proportioning valve to be adjusted to it's full limit. I wanted a better "window" of adjustability. So to reduce the amount of rear wheel braking (and gain a better window of adjustability with the proportioning valve) I decided to use a different caliper with a slightly smaller diameter piston than the present one ( front 280ZX ) in use. I chose to use a front caliper off a 1981 Toyota Cressida. This piston is 1/8" smaller in diameter (2 3/8" to 2 1/4"), which equates to about an 11% decrease in piston area. This new caliper has the same bolt pattern and spacing as the ZX caliper, the same lateral spacing as well, and with some minor filing in the area that normally rides over the outer circumference of the rotor, fits perfectly. The minor filing may not even be necessary for a good clearance, depending on how tightly the caliper is spaced over the rotor in the first place. Even the bleed screw was in the correct position. The brake pads for this Cressida caliper are corresponding smaller than the ZX pads too. It took all of about 3 hours time to swap the ZX calipers for the Cressida calipers, and to this date, all appears to work very well in brake balance department.
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