This is saved for my own referance.
The 5-lug swap is quite easy, the most difficult part will be getting the
caliper-disk spacing correct. I have done this swap on several 510's and it
works really well.
Get the front hubs and rotors off an 84-89 300ZX Turbo, or an 86-89
non-turbo 300ZX. Remove the hubs and rotors off of your 280ZX struts and
slide the 300ZX hub onto the spindle. You will note that the spacing for the
rotor does not match the caliper. You will need to make or fabricate a
spacer to match the difference between the rotor and where the caliper
mounts to the strut. Another way to do this is to seperate the disk from the
rotor and make a spacer that fits between the hub and rotor.
This is also an excellent opportunity to upgrade to a better front brake
caliper. The 300ZX disks are 11" diameter and vented-- even bigger than your
280ZX disks. One swap that I saw that worked really well was the use of
Toyota four-piston truck calipers on the 300ZX disks. The Toyota calipers
are very common and easy to find. They are however, very heavy as they are
made from iron.
Another brake caliper to use is the one off of the 86+ Mazda Turbo II's.
This is an all-aluminum, four piston caliper, and can be found quite easily.
The RX-7 caliper is very light, and there are plenty of performance pads to
be found for them. This is the setup that I am using on my 510. You will
have to build a spacer to use these calipers (but you have to do that
anyway) and you will need to match the RX-7's caliper bolt pattern (easy to do).
** note from Ross: these pads are ~4x3", a huge pad by any standards!**
The rear disks are easy to convert to five-lug. I am using 280ZX rear
trailing arms so I have direct experience with this part of the project.
First remove the four-lug disk, caliper, and stub axle from the control arm.
You will need a large impact wrench to remove the stub axle, they have a
single, very large nut that requires an impact to remove it. Slide the stub
axle out of the control arm and use a press to remove three of the four
studs. Since the four lug pattern is 4x4.5, and the 5-lug pattern is 5x4.5,
one of the studs is in the correct place. I had a spare 5-lug disk that I
used as my pattern. Slide the disk over the remaining stud and center the
disk onto the stub axle. Once you are sure that the disk is centered, mark
the other four holes. Use a drill press to drill the holes just barely
larger than the new studs that you are going to install. You want the studs
to just fit through the hole. Using the press again, press the other four
studs splined ends into the stub axle. One of the studs will be close to the
edge of the stub axle because of the 5-lug pattern. We determined there is
enough material to support it, but if you are concerned you can easily add
more material.
You can redrill your rear disks for a 5-lug pattern, which would be nice
because then your rear caliper would work, or use the 300ZX turbo rear disks
and calipers, but they are a larger diameter so you will need to make a new
caliper mount.