260DET

Its all very peculiar. Discussed it with the supplier and he said that Kuhmo recommend hot pressures way higher, high 30's, than he and others have found best. A friend of mine has found 23 cold best in his Exctas on a Triumph TR8 and he's quite methodical about such things. The other day mine were barely warm to the touch across the tread, in contrast with the Dunlops and Toyos used in the past which you couldn't bear to touch, let alone keep your hand on at all. This is all in sprint events, three to five hot laps of a circuit. Oh well, we'll see how it goes on the 'home' track in a couple of weeks time, hopefully the sun will be out and the black stuff hot

Agree with 305240, the important thing is to get the hot air out.

Thanks Clarkspeed and John. Going to drop the cold pressure down to 21 at the front, the rears heat up quicker, but no lower in case the tyre wants to roll off the rim. Have been sliding it around a bit to warm the tyres up, but the front just washes out when cold. Perhaps a bit more than 1mm toe out will help the fronts warm up quicker.

To complete the record, the conversion is proceeding as previously outlined using 280ZX CV axle half shafts with the inner CV removed and replaced with an outer. In other words, the otherwise stock 280ZX R180 CV half shafts will be used but using two outer CV joints. Some work will have to be done on coming up with a satisfactory modification of the stock internal spring tensioning and buffer arrangement. Fiddly but doable. An adaptor will be made up so that the outer CV flange can be bolted to the hub of the outer stub axles. That adaptor will be welded to the hub. Finally an observation. These tripod type CV joints would appear to be significantly stronger than the stock S30 axle half shaft universal joints. Its estimated that on my setup there will be ~20mm end float in the CV joints.

Bugger feeding and caring for them, mine won't get hot and sticky so no treats for them No seriously, the Kumho Victoracers in 225 50 15 on 8" rims on my S30 just won't heat up over a few laps. Cold pressure has been progressively reduced down to 23 psi but after a few laps they are barely warm, even with some sliding around. My theory is that that the car is now so nicely set up and with the tyres sitting well on the 8" rims that there is just not enough stress and distortion being put into the tyres to warm them up. Plus summer has gone although its far from cold. Is this a characteristic of these Kumho's? Suggestions? Hope that I haven't hijacked the topic, seemed extravagant to start another.

Not terribly familiar with the 280ZX but most cars of that era had more than adequate air intake through the front, even if most of it went through the radiator. Any engine bay heat problem is therefore more likely to be a lack of air exit from the engine bay. On my S30 turbo this was solved by adding two bonnet vents about 2/3 back, in the low air pressure area. Vents so positioned work when the car is stationary too. All this probably does not help much with this particular problem but perhaps the theory can be applied somehow Plus you can always get the exhaust system done with a heat reducing coating.

A S13(?) subframe weighs ~ 24kg bare, thats the model which had a R180 short nose diff. It has only four points that mount to the body which are flexibly insulated stock. This subframe concept seems to be used to aid assembly in the factory and to insulate the body from noise, vibration, etc. Considerations such as weight and overall body stiffness seem to be secondary. For the reasons given by Douglas its a dubious mod to use such a subframe system in a S30. The extra weight alone is a killer. Interesting to consider its use in a S130 though as Neil mentioned. Wondering how the weight aspect adds up. Don't like only having four mounting points though, particularly if flexible mounts are used. To get a stiffness benefit the subframe should be solidly tied into the body at many points. If just a cruiser S130 is required then its difficult to see the benefits which would be worthwhile if a S13-14 subframe assembly was used.

Just an observation on apparent North American spring and roll bar rates. The average NA setup uses relatively heavy roll bars and light springs to what we in Oz tend to use, although of course there is plenty of variety here. My front bar is 22mm thick, not many use thicker than that, while the rear is 18mm which is a bit thicker than average. Most springs would be in the mid 200s, depending on shocks and body stiffness, there may be a trend to use heavier shock settings with lighter springs though. Mine are 250F 300R with a half cage, went up from 275R before the half cage.

Got mine from a motor trim parts place, it was generic, shaped something like a round headed nail in section. Looks really good, adds that finishing touch.

Great minds think alike eh Yeh I agree that some sort of internal spring arrangement is required, although what effect they actually have when the car is in motion is hard to work out. My present solution is to use a different type of spring, which I don't know the name of, the coil type that compresses up within itself. Like the flat top cone shaped coil springs that are used behind internal car window winder and door handles. They should do the job and fit in to the limited space. Apparently the 720 axles are splined into the outer hub so my guess is that they would be too long. So it looks like the 280ZX axles are the go for mine.

Beautiful work but Jamie's seems to have more merit, strong five stud hubs and axles for a start.

Sounds good, probably stronger than what I'm looking at the moment. Which is using 280ZX R180 CV axles but replacing the inner CV joint and stub with another outer CV joint similar to the 280 one. Which will give CV axles that are flanged at both ends, the inner flange matching the 720 4x4 stub flange. The long end springs will have to go, they take up too much space, and an adaptor to the outer S30 stub axle will be required. Yet to check out the 720 axles though, they might be better than the 280 ones.

22F, 25R would appear to be a mismatch, unless you want to do a lot of rear end steering. Mine has 22F and 18R and will do high speed drifts on demand With 230 RWHP.

About to do something similar but using a Torsen type center in a K case R180 with the 4x4 inner stub axles. By my measurements the diff is 234mm wide at the axle faces and there is 1.054m from companion flange to companion flange, which leaves 410mm for each CV axle including any adaptors. Thats measuring at full suspension droop with 1.5 negative camber gained by extending the track, not at the strut tops. Now to find a suitable CV axle which is short enough.

There is a Japanese site where fitting Z31 rear stub axles to a S30 is shown with pics step by step. No link sorry. What mischief are you up to now Ben, the S12 not good enough?

So you have to use bolt in inner stub axles in the diff, not the clip in type? With the clip in type diff center I was looking at using 280ZX automatic transmission CV axles which seem about the right length and if so would only require an adaptor at the companion flange. Don't know if you had the same setup in the US with the ZX auto. From the sound of it, if you have to use bolt in stubs what you really need are CV axles that are flanged both ends like on some RWD Euro cars, BMW, air cooled VW, etc. Suitable length of course.

Wasn't that basic engine turbocharged and raced in the US in 280ZX's? I'm sure I've seen an article on it in the long gone Z car magazine, whatever it was called. Recall some comment that the engine had a mix of Ford and Chevrolet features.

As far as squat goes you could look at what has been done with 510 rear suspension, it is the same sort of semi trailing arm setup and there is quite a bit of info around on various sites. I'm sure that things can be done to improve it without resorting to very hard springs.

Thanks all, and John, I drive like a big girl, not a little one Buggarising around too much on the day to check tyres but started with 28psi cold and it was a barely warm cloudy day with little heat in the track surface. We reckon the pressure was too high and it needs toe out or some Ackermann as well. Caster and camber both at 3.5 seem OK. Yeh, the tyre was not working over to the telltale triangles on the edge which seems a fair indicator with these Victoracer tyres, first time I've tried them. Anyway if I think of it will post a pic after the next run to see any differences.

This is the LF tyre after some laps around a clockwise circuit, so it is the outside front tyre in most corners, the outer edge of the tyre is at the top of the pic. The LR tyre has a similar wear pattern but less, the two right side tyres are worn much less and fairly level. I have my own ideas as to why the wear is so but the more informed opinions the better

Might be an idea to do a search, ZX suspension improvement has been discussed quite a bit recently. There is plenty that can be done, apparently with great results

Slotted, not drilled, is what you want. Make? Who knows

Crankshaft harmonics, camshaft harmonics too? Lots of things affect durability and reliability, although it usually though comes down to one crucial factor which ultimately limits RPM.

That 'cone' part of a tripod CV joint houses the spring that keeps the shaft extended. Its just a piece of formed sheet metal, if its the bit I think is refered to, pics?