Rear arm/ brake upgrade to latter R31 for s12

I found on a web site that the 84-85 IRS on a Z31 300ZX is the same as we have on the S12, the brakes are also the same, they said you can fit the latter R31 1989 vented rear brakes with the twin pot rears but you need to fit the IRS arms too so the calipers bolt on, question is has anyone done this or seen if the arms look much different?

The rear discs are also 290mm over the 259 of the S12.
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Cheers
Michael

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S12 Silvia/FJ20 NA engine/320Hp forest racer rally car
Subaru STI V5 Type R 380Hp/ 0-100-4.2 road rocket

According to Options Magazine reply to a japanese reader they said that r31 brakes are swapable with s12 83-88 200sx. They will both on just change brake lines and master cyclinder.
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Power is Nuttin without control!!!!

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I found out that the Z31 280 ZX is the same rear end with regards to arms and brakes, it is the latter 89 on that uses the larger discs and vented discs, but you need there arms to bolt the calipers on too, the only difference was the brake mounting were 5mm different on the arms.

I am sure the calipers are all still steal single poters with slider pins, i seen a set of alloy twin pots on a latter 300zx turbo, which uses the same discs as the latter 89 Z31, so more research i will see if they bolt on with the latter arms.
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Cheers
Michael

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S12 Silvia/FJ20 NA engine/320Hp forest racer rally car
Subaru STI V5 Type R 380Hp/ 0-100-4.2 road rocket

I'm sorry to tell you this bu this swap has existed for quiet some time. The Z31 300ZX was technically split into 2 generations. There were numerous changes but the one in question came in the 2nd gen. I'm guessing they did the same w/ the R31 Skylines. The track was increased by 20mm total, 10mm on both sides. Yes, you do have to swap the whole control arm to use the brakes, which include vented larger rotors (16" wheels MUST be used) and 2 piston calipers. I do believe these are the same rear calipers used in the later Z32's but I am not sure. If this were try it would be best to use the Z32TT's becuz they are aluminum. On the brake lines... the bent tube lines should be different but the soft lines should not. Really as long as you get the WHOLE arm (brakes and all) you should be cool.
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[jeff]

87/88 SE V6 icon_mrgreen.gif
[like me, its starting to fall apart]

"You only hurt the one you love."
That may be true, but better said:
"You only hurt the one who loves you."

Thanks Jeff, I thought it would be old news icon_biggrin.gif

While on the topic of the twin spot alloy calipers, has anyone had and luck bolting them to the early arms same as our and use the smaller discs, i know the disc will be thinner, I can use some spacers.

The whole deal is i have mazda RX7 4 pots on the rear with an adaptor, it uses 280mm vented volvo discs, it runs a brake bias but still has too much rear brake, also when i just did the crontrol arms mods i couldn't beleive how heavy the sucker was, i weighed the discs and they are 12lbs more than the std ones, so i figure if i use the std discs and if the 300z alloy calipers bolt on it should all turn out right.....I hope icon_eek.gif
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Cheers
Michael

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S12 Silvia/FJ20 NA engine/320Hp forest racer rally car
Subaru STI V5 Type R 380Hp/ 0-100-4.2 road rocket

There is no easy way to do it. Maybe no way at all? If you can fabricate something up thats great but nobody who has ever owned an S12 or Z31 has made them work. You'll prob just have to upgrade the front brakes to match your RX-7 rears. (BTW - you might want to do a write up the RX brakes) icon_biggrin.gif The weight thing is why I haven't done the swap actually. Bigger brakes come at a price. Plus I haven't really exhausted my stock brakes yet. Sooner or later I will have to do it though.

PS - Y didn't you put the RX 4piston's up front? they'd prob gone to better use.
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[jeff]

87/88 SE V6 icon_mrgreen.gif
[like me, its starting to fall apart]

"You only hurt the one you love."
That may be true, but better said:
"You only hurt the one who loves you."

Thanks,

I have the same volvo discs up front with the 300ZX pots already, twin master cylinders with different sizes, no booster and a pedal box.

Next time i am at the local z wrecker i will have to check the bolt holes out and see if i can make an adaptor to bolt on the calipers.

The STD S12 rears are still on the heavy side, and i'm not sure i can get a Ferodo DS off the shelf, where the alloy 300zx twin pots use the same pads as the Subaru Jap spec STI, so there is a good selection of pads for them.
_________________
Cheers
Michael

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S12 Silvia/FJ20 NA engine/320Hp forest racer rally car
Subaru STI V5 Type R 380Hp/ 0-100-4.2 road rocket

No booster?!?!?! doesn't that require a LOT of pressure on your part?

I must admit I am having a slightly hard time understanding some of what you are saying. Its a bit choppy but sounds really cool. Is there any way you could go more indepth and tell us what part exactly you used? I mean I had heard that the CA cars could use toyota 4pots up front but I have heard nothing about volvo rotors (year model)??? have you already switched to the later z31/r31 front hubs and calipers? to use these rotors? which 2pot nissan calipers do you have up front?
_________________
[jeff]

87/88 SE V6 icon_mrgreen.gif
[like me, its starting to fall apart]

"You only hurt the one you love."
That may be true, but better said:
"You only hurt the one who loves you."

This is really interesting. I would love to see some pix of all this some time. I know I never would have thought of going that far w/ it.
_________________
[jeff]

87/88 SE V6 icon_mrgreen.gif
[like me, its starting to fall apart]

"You only hurt the one you love."
That may be true, but better said:
"You only hurt the one who loves you."