While the Stock 84-86 Z brakes are pretty good, the 87-89 Turbo brakes are even better. They have larger, stronger twin piston calipers up front and larger rotors with bigger brake pads yielding more contact area. These brakes swap right on provided you have the 87-89T front hubs as well. It is extremely easy to do, simply remove the front caliper (with bracket), rotor and hub assembly, then install the other parts the same way. Make sure you re-torque to factory specs after swapping the hubs. I can't believe how many questions I get about this; that is ALL there is to it. Here is a comparison:
The rotors I got on the 88T were alright, but down almost to minimum thickness, so I decided to get new ones with the new Axxis Metalmaster pads I was ordering. Unfortunately I ordered from irotors.com. They sent me slotted and cross-drilled rotors when I though I was ordering OEM quality replacements. They also sent me CTEK Metallic Brake Pads instead of the Axxis Metalmasters they specifically said they would be sending me. Then they made the claim that they were an equal quality pad... whatever. They don't look awful. Stopping power is AMAZING; I can lock the brakes at highway speeds and they can easily handle multiple stops from 100 without fade (I'll test the limits sometime later, once the pads and rotors are broken in).
Side note: most cross drilled and slotted rotors are cosmetic ONLY.
Upgrading to Z32 quad-piston calipers.
Though they're not leaps and bounds better than 87-89T dual-piston calipers, the Z32 calipers offer a few nice advantages. For one (if you get the aluminum) they are far lighter than Z31 iron units, and this will reduce the unsprung weight of your front suspension as well as the cars overall weight. The Z32 pads have slightly less swept area than 87-89T pads, but the caliper has more clamping force.
To swap on Z32 front brakes you will need:
The caliper installation is very straight-forward. Bolt the new calipers in place with the washers to space them outwards .170" (in order to center them on the Z31 rotor, they will already be centered if you use 87-89T Z31 rotors). The Z32 lines have two parts; a solid line and a hose. If your hard lines are intact, simply obtain a set of front Z32 brake hoses from anybody who makes and/or sells them except for Demonspeed who will rip you off. PDM racing also sells a conversion brake hose kit for 240SX's that is a direct fit for the Z31 as well. The PDM lines are what I used and they worked great.
Another nice benefit of the Z32 calipers is their appearance when painted; very nice.
As for the 87-89 rear vented brakes on 84-86 cars:
All of the 87-89 rear control arms and brakes have to go together, there is no way around it. If you want the vented rear brakes, you need the 87-89 rear control arms; each of which are 10MM longer. I installed new poly bushings in the new rear control arms; I swore I would never do that again, but I did. (Note: 84-86 and 87-89 use the exact same rear brake pads. The calipers themselves are slightly different and go along with their respective rotors; so they cannot be interchanged.) I used this rear
suspension, but it was almost shameful to replace my prefect, spotless 84 rear suspension with something so rusty. I painstakingly wire brushed and sanded the control arms (and used my existing 84
cross-member) and coated them with POR15 and then rust resistant enamel.
84 Rear suspension with open diff:
88 Rear suspension (no diff):
This is what ends up happening. The suspension is 10MM wider on all corners, so
now your wheels will sit more "out" although not nearly enough to rub on anything.
