Leon

I know your pain, high performance tire options for wide 15s are slim. Toyo does make R888R's in 235/50-15, a buddy is running them on his 15x10s. That's what he settled on after we researched the hell out of the current options. The other contenders were Hankook RS4s in 245/40-15s and Achilles ATR-K in 245/45-15. You're not going to find decent 255 or 265s unfortunately.

Go for slight toe-in at the rear, 0.10-0.20 degrees total.

"Good" depends on your use case. Are you tracking it and how strong are your arms? Take a look at John Coffey's recommendations, they're in the first post of this thread.

In a vacuum, both toe-in or toe-out would cause dartiness as single-wheel inputs will steer the car one way or the other. I also don't agree with toe-out being better for turn-in, as it decreases your yaw rate gain, i.e. you need more steering input per given corner radius. Now if we take ourselves out of the vacuum, there are other effects that influence static toe settings such as suspension compliance (mostly controlled by bushings) and kinematics (bump-steer). I haven't seen any published K&C test results on an S30 chassis but if you've installed poly bushings everywhere, keeping toe close to zero with a dab of toe-in, as you have it, is a safe bet. The cheapest way of adjusting rear toe with stock arms is eccentric bushings. I've never used them but I don't see any other way around that other than adjustable arms or doing a bunch of fab work to slot the transverse link supports and splice in a turnbuckle into the transverse link brace (this has been done and can be found by searching).

Higher caster should have more of a centering effect due to the increased trail which increases the aligning moment on the tire. The caveat is that with the steering geometry of the Z (including but not limited to), there's a point where steering forces reverse and there is a wind-on effect where the wheel steers itself towards lock. This is all a long-winded way of saying that bringing caster back down will not improve your return to center problem and that return to center will suck no matter what, when you reach a certain critical steering angle. However, I haven't studied the Z's geometry that carefully so I very well could have overlooked something. Adding more front toe will make the car dartier, that looks good where it is. The added negative camber may make the car dart a bit more but it's a smaller effect than toe. I really think that rear toe is doing you wrong plus maybe some other mechanical factor that we haven't found yet. Have you checked your steering system for slop (ball joints, rack, etc.)?

So did anybody end up trying this setup on 15" wheels?

I made an opportunistic purchase today! I've fantasized of going to 15X8 Watanabes (I know, so blasé) for years. A buddy tipped me off to a fresh set for sale locally and I decided to go for it. Really looking forward to seeing how they fit the car and keeping my fingers crossed that they'll work with the rear disks that I'm about to install. So now that this has finally happened, I'll have to liquidate a few things from the hoarde...

Strange, I wouldn't expect steering feel to dull after increasing caster/trail. It comes down to what you mean by dull steering feel. Is it the steering feedback that's dull or a lack of body rotation per steering input? To me, it sounds like the latter and should be helped by reducing your rear toe. A huge front bar and no rear also doesn't help.

That's a lot of rear toe. I would dial that back to no more than 0.10° per side. Do you have your previous alignment specs to compare to?

I'm not so sure about that cantilevered rod-end boss. That's a fatigue failure waiting to happen...

Cam timing looks ok and shouldn't cause the issues you're seeing. The shiny links are used to set timing on chain install, the groove and notch are used for all other checks and adjustments as OP has done. My money is on a calibration or crank sensor issue.

Yup, that's a Traction Avant! Very cool.

Sectioning is complete! Will sandblast and paint the struts as soon as time allows. Once they're painted, I'll reassemble with fresh bearings and finally install the rear disk brake kit I've had lying around for about 4 years now. Really looking forward to actually having some bump travel! It feels good to be working on the Z again. There are a few more niggling issues to deal with, mainly refining the tune and getting the speedo and tach working reliably.

Your oil temps will be hotter on track than autoX or regular driving. Hotter oil is less viscous and easier to pump, thus pressure drops. It's not necessarily a sign that something is wrong but if you're worried, install an oil temp gauge. If you're running synthetic, you should be fine to about 280°F.

Great work Ryan! Love the tidy engine bay. Any plans to go to the dyno soon? I know you've been trying to set that up for a while.

Setting the geometry up to get what you want at nominal ride height and steer is simple enough but one of the big complications you're not factoring in is that the virtual pivot/kingpin axis moves around during steer, unlike the single arm setup. If you look back at the Pontiac video, this can be visualized really easily and you can see that scrub increases on the inside tire and decreases on the outside during steer, in this case. Also, caster drops on the outside and increases on the inside. The two things you don't want. However, going to a split-lower arm on an S30 would result in a compression link setup instead of tension link, as Pontiac (Holden) has done, so I bet the resulting geometry would be more favorable regarding caster and scrub. Still, a full kinematic sweep is needed (ideally K&C) to be sure you're getting the effects you want. As an aside, TC rod positioning on the control arm does have an effect on geometry, e.g. caster gain (therefore kinematic anti-dive) and bump steer. It can be seem as a sort-of front semi-trailing (leading) arm. This is minutia in the sandbox that we're playing in but worth noting that it does do something.

Bummer. They should've come with a warranty card when you bought them. Contact Tokico and see if they can give you any sort of goodwill.

You've lost the gas charge so it's done. Hope it's still under warranty...

In my case, they ate the OEM guides in about 1000 miles.

I've had similar poor experiences with SI valves, with the caveat that I ran them on OEM guides. When I talked to Dave about it, he mentioned hearing about others with similar issues. Went with OEM exhaust valves and Supertech intakes on his recommendation. Had him work the head on the second go-around...

You used the b-word... If I may summarize your post, you want to convert the front and rear suspension in your 280Z from struts to dual A-arms because you feel like you'll have "more adjustability" and "the suspension will move around less"? And because your Corvette couldn't keep up with Porsches in slow corners? Then some stuff about roll centers that showed a fundamental lack misunderstanding of what roll centers do. You might as well say, "if your anti-roll bar rates were more equal, it would be a better setup". Roll centers are just one component of anti-roll which itself is just one component of vehicle handling. It's all a system. You will be frustrated and lost if you're only looking at single characteristics in isolation. You have to understand the problem first, ask yourself the right questions, research and execute. In reality, that's an iterative loop. Currently, there is a lack of understanding and lack of clarity as to your wants and therefore needs. I've seen the Apex kit and while nicely crafted, it represents the above statement.

Strut sectioning is underway...

Forgot to mention, I threw the wheels on the tire balancer and they all had borderline-to-excessive road force (14-28lb). That explains the slight vibration in the steering wheel (combined with the excessive play in the steering rack). Unfortunately, looks like the tires have all been flat-spotted from sitting stagnant for a few years when the car sat. There are no issues with driving on them but the slight steering wheel shake is annoying. I'll have to accelerate the wear a bit, I think. I'd like to get some 15X8 Wats as the 16" Panasports are just a bit too big for my tastes but the tire options are unfortunately limited to either some cheap no-seasons or R-comps. Might just go for the 15s and just send it with some R-comps since it's a fair weather car. If anybody's interested in some 16X7 zero-offset, almost brand-new Panasports let me know and it may just send me over the edge... I'll also have to find a good source for Wats.

It's been long enough! The car has been on the road for a few years now and I needed to catch up on some maintenance and upgrades this past Friday. On the to-do list was some maintenance, mainly diagnosing a clunky front end, as well as a new speedo cable and the long-awaited LSD and fuel pump install. There were wins and losses on this day! But first, the wins... It's always nice to have friends help out to make things go quicker and today was no different. We got the rear end out without much trouble, it's nice to work on a freshly put-together California car. The LSD is on the left, along with some cruddy old axles I had lying around. Those will be addressed later... While the diff was out, we thought about how to tackle my rear toe issue. The chassis doesn't look like it's ever been hit but something is definitely off. Here are the rear toe numbers from a while back: For the sake of on-car adjustability, we decided to slot the transverse link brace. I calculated, based on rough measurements, that we'd need ~1mm slot so we milled off 2mm. Slotted vs stock And a major win, we're finally at zero thrust angle! Goes to show that it doesn't take much to have the rear toe go out of spec, especially considering a stock Z has no adjustment back there. (The amount of cross-camber is annoying and I plan to find a way to fix that as well) The LSD install went smoothly and we finished up late that night. It's clunkier than my old diff, yet to be determined whether it's the backlash or the u-joints in the axles. There's also a bit more gear whine but not really in cruising RPM ranges. Filled it with Redline GL-5 diff fluid which has friction modifiers in the formulation, the clutches are nice and quiet so far. Acceleration is definitely peppier but it's not quite the 80mph cruiser it used to be. I haven't had a chance to push the LSD much yet but that'll come! Now for the other stuff... After a quick investigation, the clunky front end turned out to be a loose FR gland nut. We snugged up the rest as well. Channel locks did the trick without any drama or disassembly. However, that wasn't the only clunk. Grabbing the wheel at 9 and 3 also revealed a lot of play in the steering. We initially thought it was an inner tie rod but it turns out the play is internal to the steering rack (!). I plan to see whether I can make any adjustments to fix that. If it's too far gone, I have a spare rack I can toss in. If that happens, I'm curious to measure the rack ratios to see if there's a difference considering my spare is a 240Z rack and I have no idea what's in there currently. The speedo cable went in without much fuss but the speedo is still non-functional. Haven't probed further. I did put a matching 19T (white, 3.9 diff) speedo gear into the tranny so the speedo should be accurate once it's actually working. We didn't have time to do anything about the fuel pump so that's been postponed. The major annoyances left with the car is the lack of bump travel causing the suspension to bottom out when it shouldn't and the rev-hang issue. We'll be sectioning a spare set of struts in the coming weeks to deal with the former. Once those are dealt with, the refinement level and enjoyment will go way up.

No, it's not trolling and is indeed carefully chosen. Read the thread.