Hi guys

I'm currently running a std rear brake setup but would like to go to an R31 disc rear, essentially to match the R31 front I'm running. Do you get a natural increase in rear track in doing this? If so, does anyone know by how much?

Thanks, Brett

Zero increase

.....because the thickness of the disc rotor hub equals that of the original drum

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Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

Get a set of 240k trailing arms and change the shockie mounts to suit the 1600 shocks (cut and shut from original arms)
May not be road legal.
Or change the socks to suit.

This will give a wider track, about 10mm each side I think from memory. Bigger stronger arms and bearings too.

Thanks guys. It was more a matter of evening out the track rather than a brake upgrade per se. Eg I've got 14x6 +35 front and 14x6 +9 on the rear, and have never really been happy with the way it looks. Thinking of going 15" now, but with equal offsets.

Re 240K trailing arms and rear brake upgrade. 240K units are similar to the 510 trailing arms, but different in a couple of arguably important ways. The spring seats are "beefed up" by virtue of an insert welded in 15-20mm from the bottom. To maintain the ride height if installed in a 1600 / 510 you will need slightly shorter springs. The factory installs a doubler plate to strengthen the area just ahead of where the axle goes through the arm (which is where 1600 /510 ones bend - I broke a couple when competing in rallies). Shock mounts do not line up, so you will have to fabricate new ones or cut off from donor 1600 /510 ones. You will need to make up a jig to ensure correct location when you weld the shock mounts on.
There is another reason for choosing to install 240K trailing arms: Z31 5-stud axles fit: you will need axles, bearings, spacers, nut and inboard flange from the Z31 . You need to make sure that the adjusting piece (spacer) between the bearings is the same length. They come in three lengths and most common ones are the middling size. They are marked "M" in the 240K = "B" in Z31. If you choose to use Z31 axle flanges (four bolts - inboard), then some cutting and welding is needed.
Fitted to 1600 / 510 with Z31 axles mean I can run R32 / R33 16 x 6.6 +40 offset wheels and these JUST fit with slight rolling of the guards (a hammer job). Wider track and matches the front of my car which is 35mm wider track because I have built a rack-and-pinion conversion with 5-stud hubs and 4-spot callipers. Both front and rear wheels fit within the guards without flares. The car looks surprisingly original, but has more aggressive stance due to wider track and 5-stud wheels with 205/45/16 tyres.
I made up custom brackets to fit R31 calipers and Z31 rear discs (~290mm).

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Things work best when it matters the least, and ...

240K trailing arm 5-stud conversion installation is complete ... a couple of points to note: The measured track increase compared to Datsun 1600 is 15mm each side, giving a total of 30mm increase. Datsun 1600 Lovells lowered springs are a touch too long because of the welded-in insert under the spring in the 240K trailing arm. I have used lowered King (KDRL-07) springs for Datsun 240K. Time will tell if this was the right choice. When I fabricated the lower shock absorber mounts I made them stronger much like the ones on HR31, but positioned in the same location as the Datsun 1600. This means installing coil-overs at at later date will be a straightforward matter of removing springs and shock absorbers and bolting up the coilovers (Techno Toy Tuning, Ground Control or similar?). Fitted to the trailing arms I chose 4-bolt axle flanges from Z31 turbo ( I think HR31 flanges are the same ??) and inboard I have used axle flanges from Nissan / Datsun 720 front diff (R180). In between I am using custom flange adaptors made from 6061-T6 aluminium that are effectively 15mm thick, combined with Porsche 944 CVs and CrMo axles. I went for CVs because their smooth operation makes the Datsun R180 Quaife Torsen LSD I am using work more smoothly than UJs would. Axles (both sides) are the same length as R200 LHS ones sold by Wolf Creek Racing in the US.

A couple of minor mods were needed to ensure trouble-free routing of handbrake cables for R31 calipers.

This conversion looks seriously neat. In service it should be strong, smooth, quiet and very reliable.

Upon reflection, as always, there are a couple of things I might have done differently.

The Z31 axles are heavy and have a big circular flange outboard where the wheel bolts up. It would have been nice to trim this flange by profile cutting to remove some of the unnecessary material around the circumference of the flange and between bolts: this work would have to be done using a machine shop with a wire-electrode cutter. The only problem is additional cost.

Going straight to HR31 trailing trailing arms with coil-overs would have been simpler, especially with a Datsport adjustable rear crossmember fitted. I have measured the difference between HR31 trailing arms and the 240K setup described here: HR31 trailing arms have significantly more (negative) camber, but toe angles seem to be about the same. Shock mounting points (coil overs on HR31) are 100mm higher, but otherwise follow the same line of action. 240K trailing arms came from the factory with extra plates welded to strengthen them (compared to Datsun 1600 ones), and are heavy as a consequence. HR31 arms are significantly lighter.

I apologise for not posting photos, yet. They are coming.

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Things work best when it matters the least, and ...

Nice mate, do you have pictures of the setup?

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Current Garage:

1971 Datsun 1600
2019 Mazda 6 Touring Wagon
2009 Holden SV6 Sedan

Wheels are R33 Skyline 5-stud 16 x 6.5 40 offset, no spacers fitted either front or rear.

Yes, it's my daily drive and I wanted to have just a little less than original ride height and good suspension travel to cope with "traffic calming devices" and potholes.
No: it doesn't need to scrape its belly along the ground and have zero suspension travel to make it go around corners like it's on rails.

Spring rates at each wheel, front and rear are same: 380lb/in

Total rear track increase = 30mm

Total front increase with rack and pinion steering is 35mm.

Conversion of DR30 / HR31 to 5-stud with Z31 axle is same as used here for 240K arm.

240K arm is very strong but heavy. If you are looking to save rear arm weight then HR31 with coilers and, say, 230-260mm disc would be a better way to go, with Golf Mk4 calipers perhaps.

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Things work best when it matters the least, and ...

Nice work

Also see photos and details at thread "Strong C.V/Drive shafts and Big Clutch options?"

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Things work best when it matters the least, and ...

The cool thing with the HR31 arms is that R32 brake upgrade is a bolt on affair...

If you wanted to keep uni-joints, other than making adapters, what uni-joint hub ends fit the HR31 rear hubs?

240K only? or did other models come with the larger inner 35mm spline and uni-joint?

Alan, put a build thread of this beast up if you haven't already...

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1972 Datsun 1600, S14 SR20DET Engineered (204rwkW @ 17psi.)
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