Z32 / M30 2 pot rear brake conversion

gerrybg · 06:41:05 PM / 03-Jul-08

The Z32, R33 etc etc, (all use the same rear brakes) rotors are 63mm 'tall', the Z31 87-89 are 57.2mm. So almost 6mm difference. My spacers are 5mm, so that should be close enough.

I could have got hold of a backing plate off a HR31 JDM import skyline turbo, from what I'm told they have the same rear end as an F31 in the US. After a bit of research I found that HR31/F31 guys have had to space Z32 calipers out 6mm to run Z32 rotors and calipers ,(also the Z32 rotors just cover enough of the brake shoes for them to work). Using their own HR31 rotors the Z32 calipers fit fine with no spacing issues if you follow. This tells me that the HR31 rotors must be close on 6mm taller again than the Z32 ones. So I figure that the F31/HR31 drum hbrake shoes etc are 'taller' than the Z32 stuff, and would probably hit the back of the hub.

(Actually one of the Aus members on here did a rear conversion using Y31 Cima rear bits, which are the same as F31 also. The hub/axles on those are longer and this is what gives them the backspacing behind the hub face for the rotor and park brake stuff, I've seen pics of it and knew from those.)

So I'm going to use Z32 backing plate, drum brakes rotors and calipers. Also I've found out that the 2 rear handbrake cables on F31 and HR31 attach together the same as s12 and Z31 ones in the middle, but on the ends are like Z32 to operate the drum brake. So I've got hold of a pair off a HR31.

So hopefully with all the right combination of parts should all bolt up.

I'm a scrounge hound and have got all this stuff for very little as far as $ goes, otherwise I wouldn't have bothered. When it all gets here we'll see how it goes.

gerrybg · 07:25:17 PM / 21-Aug-08

The HR31 backing plates only lined up for two holes when turned about 30 degrees. The bolts are also metric 10mm rather than 8mm for the s12 and Z31.

I have drilled the 2 holes that line up to 9mm and then retapped them to 10mm which was pretty easy. I've then given the trailing arms to a machinist with a bench drill and he is going to drill 2 holes in each to match the other 2 holes in the backing plates.Then it will all be a bolt up with all the parts I have, (I got my Z32 rear calipers with all the lines, hoses and good pads the other day).

I got my HR31 hbrake cables and they are a perfect fit for the s12. The front ends that join towards the front are exactly the same as the s12.(This I believe is the same for M30 cables).

So for people in the US what you could do if you wanted to go to this trouble, (which I wouldn't have bothered if I hadn't got all the parts for next to nothing like I did), You would just use M30 backing plates and hbrake cables and trim off the edges to accomodate the bigger Z32 rotors.

gerrybg · 11:20:56 PM / 09-Sep-08

Finished my Z32 2 pot rear brake conversion, wasn't to hard, getting the bits together was the hardest part.

I used:

87-89 Z31 trailing arms.(Could be done with normal s12 trailing arms with bigger spacers but starts to get complicated and messy)

Brake backing plates and hbrake shoes and bits from HR31 JDM Skyline or Y31 JDM Cima, (same as the M30 in the US).

handbrake cables from a HR31 JDM Skyline, (US would use M30)

5mm slip on spacers

HR31 or Cima flexible brake lines (US M30)

Z32 rear calipers

Z32 rotors

Z31 5 stud hubs, (not necessary you can stay 4 stud if you wish)

Steps:

1. Widen the diameter of central hole in the backing plate to clear the Z31/s12 bearing tube which is a few mm to wide, (I just used an angle grinder and die grinder)

2. 2 diagonal holes in the backing plate will line up with 2 on the Z31/s12 arms. Redrill these holes using a 9mm drill bit, then retap them to 10mm x 1,25mm thread

3. Bolt the plate on then mark the 2 other holes that don't line up and redrill holes in the trailing arms using 9mm drill bit and tap to 10 x 1.25mm, (I got an engineer with a pedestal drill to do this for me cost $30 for both trailing arms, I have since bought a pedestal drill so next time (not that there will be a next time!!) I can do it myself

4. Cut the outside portion of the backing plate off with a thin cutting blade in the angle grinder, (its to narrow for the Z32 rotors and you only need the centre bit the brake shoe mechanisms mount to.)

5. That's about it really, then everything bolts up.

I'll get pics when I get time.

I haven't bolted these arms up to my car yet, I'm waiting on my rear srping mounts from megan so i can bolt everything on together and be done all at the same time.

Oh almost forgot to mention with this brake setup the track is 15mm wider per side so you may need a guard roll with your tyres pushed out this much, depending on combination of wheel width, tyre size and rim offset.

gerrybg · 07:41:43 AM / 25-Sep-08

Here's links to the pics as promised. I haven't swapped the stub axle in yet. Last photo shows where I've redrilled one of the new holes required.

http://img229c.imageshack.us/img229/7537/reabrake6xm3.jpg
http://img229.imageshack.us/img229/8603/reabrake4sg1.jpg
http://img229.imageshack.us/img229/4736/reabrake1wf3.jpg
http://img229.imageshack.us/img229/5025/reabrake2co1.jpg
http://img229.imageshack.us/img229/3158/reabrake3jc9.jpg
http://img229.imageshack.us/img229/4475/reabrake5xu7.jpg

IggyEGuana · 11:33:45 PM / 25-Sep-08

E-brake performance question here.
Stock S12 setup really sucks.
Would upgrading to late Z31 vented be enough to get lock on demand or would it be advised to step up to this drum setup? I've heard these types of e-brakes usually work very very well.

mod_mastaz · 09:32:48 AM / 26-Sep-08

My vented rears with hawks HPS are pretty great, although I don't yank my e-brake left and right. The stock e-brake honestly is fine with some decent pads. The vented brakes only cool better than the solid disks. They use the exact same brake pad and the surface area is still the same. It's only moved out like an inch or so for more leverage.

al3x · 10:00:49 AM / 16-Oct-08

Good work Gerry!

also noticed you have the rear threaded coil over section, were you able to purchase it seperately to the set?

gerrybg · 10:14:11 PM / 16-Oct-08

Yeah I did, I found a NZ distributor of Megan products, (there are none in Australia that i could find). They were just arranging a container of stuff to be shipped from the US, and I asked them if they could just buy the adjustable spring seats from megan for me and they were able to arrange it.
Because they were already getting a container I didn't have to pay freight from the US, just postage from NZ, which was only $25 or something.

I have some s13 koni yellow rear shocks here, and a few sets of coilover springs to run with them.

al3x · 03:24:40 AM / 17-Oct-08

Sweet, was it TNT Performance? They seem to be the only NZ distributor.

I picked up a set of S15 Tein Flex coilovers so will try out the rears and see if they can be adjusted low enough, the tube is really long!

gerrybg · 05:32:09 PM / 25-Oct-08

Yep was TNT, (the South Island branch)

tuhsty s-12 · 11:36:53 PM / 28-Jan-09

Quote from: al3x
Sweet, was it TNT Performance? They seem to be the only NZ distributor.

I picked up a set of S15 Tein Flex coilovers so will try out the rears and see if they can be adjusted low enough, the tube is really long!

should try s13's they are shorter i believe

tuhsty s-12 · 11:40:49 PM / 05-Feb-09

bin lookin at this converion...would it be possible to do with s12 arms/hubs and z32/r33gts backing plates..cuz the r31/m30 gonna be impossible to find where i live

i really need ah e-brake wid sum bite n the hub/rotor set up would be perfect with project mu shoes n pads

seb.racing · 07:08:47 PM / 28-May-09

Z32 rear swap is completed? you have other pictures of swap?

is a complex assembly

kyskater · 05:06:25 PM / 26-Sep-10

Can I just take the whole trailing arm from the m30

gerrybg · 07:53:16 AM / 27-Sep-10

Not farmiliar with the M30 as we didn't get them here. If the shock mounts in the same place as an s12/Z31 it would be okay, but I suspect it doesn't, it is more like skyline R31 R30 etc which mounts the shock on 'stub' sticking out from the trailing arm.

BattleFairy · 02:33:06 PM / 28-Sep-11

can someone reupload the pics?

Quote(Could be done with normal s12 trailing arms with bigger spacers but starts to get complicated and messy)

can someone explain me that point?

ASid · 03:58:08 AM / 23-Jun-13

Hey, I finished my HNR32/BNR32/Z32 2 pot rear brake conversion (without hand brake) on Nissan Silvia S12 '84 FJ20E (European market) 290mm rear brake discs. Maybe it will be interesting for someone.
Previous owner installed aluminum brakes from HNR32 (Nissan Skyline R32 4WD RB20DET, brake discs 280x30mm front, 297x18mm rear), the same as on Z32, and rear brakes the same as on GT-R 32 (BNR32). I have S13 suspension on front, so that's clear. At rear brakes was installed on original S12 brake disc 290x10mm (i think all was bolt-on), but that disc is too thick.

So I bought brake discs from Toyota RAV4, original code 43512-42010. Gave them to turner - reduce external diameter from 302mm to 290mm, and increase internal diameter from 62mm to 68.09mm. Drilled 3 holes on each disc for 4 lugs hubs.

Original Disc | Z32 disc | RAV 4 disc

Also I bought original brake pads from Subaru Impreza WRX (same construction of calipers) - code 26696-FA000. I prefer them because it's break pads + all mounts + all plates in one pack!

So here we are:

All fits perfect

Also I cut a bit baffle-plate.

pakii-afa · 11:24:48 PM / 07-Dec-13

old thread i know but question. i heard that only z31 turbo trailing arms were 10mm wider. but is it true that all z31 arms are wider?
and if i was to use my stock s12 arm, how big of a spacer would i need to machine to have full z32 rear 2 pot brakes with functional ebrake.

vegasS12 · 02:44:33 PM / 09-Dec-13

Quote from: pakii-afa on 11:24:48 PM / 07-Dec-13
old thread i know but question. i heard that only z31 turbo trailing arms were 10mm wider. but is it true that all z31 arms are wider?
and if i was to use my stock s12 arm, how big of a spacer would i need to machine to have full z32 rear 2 pot brakes with functional ebrake.

yes I believe only the Turbo (vented rotor) Z31's arms are 10mm wider.