Sway bars and alignment with Xida GS
 

I just finished installing my shiny new Xida GS, as well as poly bushings (modified using Teflon tubing as sleeve bearings), so now I need to figure out what to do about the alignment and the big front sway bar that I already had. This is purely a street car for now (albeit an exuberantly driven one).

The Supermiata alignment page mentions that the street alignment works best with a bigger front sway bar, but the Xida GS page mentions that they ride best with stock sway bars. I have a Racing Beat tubular front bar on the car (which, btw, is in theory 1.5% less stiff than the 1" solid bars...). Judging from the short test drive with a completely randomized alignment I am, to say the least, thrilled with the ride quality even with the big bar. I've got my ride height set at 5-5/8 front and 5-3/4 rear.

So, should I just keep the big sway bar and use everything except the ride height from the Supermiata street alignment? Would there be a significant benefit to switching back to the stock sway bar other than making the already-excellent ride quality even better? With stock sways, what the heck do I do with the alignment?

Go read the how to Xida thread. I asked the same question about running xl length shocks with bigger front sways and doward said that it was recommended for ride comfort mainly. Running a bigger (but not unbalancingly large) front sway won't have negative consequences.

As for the alignment, I don't think that is suspension dependent. I don't even have Xidas yet and I've liked their alignment for some time on my garbage suspension.

You may not be able to get to the advertised alignment settings at a different ride height - lowering the car makes a lot more camber available than there is at stock height (I tried this myself). Alignment will certainly affect (perhaps as much as anything else) the handling characteristics of the car, but without first getting a sense for how it feels with the parts you want to run, I would not make any changes. Go with alignment numbers anywhere between supermiata-spec and stock, put on the big front sway, see how it feels. Make adjustments later if you don't like something. Alignments are fairly cheap!

It does seem that two new and relevant posts have been made to the How to Xida thread since I read through it. That makes me feel a little better about keeping the big sway bar. I wouldn't want my Miata to be TOO soft and supple!

I doubt I'll have a problem getting to the street alignment camber settings. When I put everything back together I just put all of the alignment bolts roughly in the middle of their range, and I ended up with easily visible negative camber.

So unless I hear from someone who knows better, I think I'll go with -1.4° front, -1.0° rear camber; 0 toe to slight toe out front, 1/8 toe in rear; a bunch of caster; and my current height of 5.625 front, 5.75 rear.

I'd definitely keep the bigger front bar. I have the FM Fox, hollow Racing Beat front, OE rear with 949 endlinks and 949 street spec alignment. No complaints. The car just goes..... and you should be able to adjust the Xida to the softer end of the damper setting to get a comfy ride when you want it.

Also, make sure the sway bar is properly lubed. My FM front bar uses poly mounts and it was all dry and seized up when I took stuff apart to install the Xidas. Dry mounts will increase front stiffness a lot. Car used to be noticeably understeery, now is neutral again.

Indeed. I went to great lengths to ensure that there are no squeaks or binding on this suspension. I bought a bunch of PTFE tubing, bored the inside for a snug fit on the steel sleeves, and (with great difficulty) bored the poly bushings for a tight fit on the tube. So there are basically Teflon bearings between the bushings and sleeves. I also greased everything thoroughly and installed grease fittings, with grease holes drilled through the bushing and the Teflon. The sway bar got Teflon tape, grease and grease fittings.

I got the car aligned as described, and I'm very happy with it. The combination of great ride quality, high roll stiffness and laser-quick turn in is extremely impressive. I haven't spent enough time near the limit of grip to say anything definitive about the front/rear balance yet, but it's close enough to neutral that the couple of exuberant turns I've taken have not shown significant oversteer or understeer.
​​

After a good weekend autocrossing, my mind is now clear: one needs a tire pyrometer to make educated adjustments to alignment and setup.

Very true for road course, not so much for autox.

Autox courses simply aren't long enough. If you try to even the heat across the tire at an autox, you're probably giving up time to just running more camber.

If the tire is happy, isn't everybody happy? Why would an even temperature profile lead you astray?

In my case, I've got a slightly lowered car (on FM Fox coilovers) and I measured 15 degrees hotter at the outside front. More camber seems like the right answer - alignment wouldn't give me any at this height (I'm already at 2.1 degrees), so we reduced the front sway stiffness (going from stiff to soft on the adjustable FM sway bar) to allow more roll and thus camber gain - temps improved to 10 degrees difference, and the car felt noticeably better. In this example, the temperature pointed me in the right direction, and led me to make a big adjustment that would not have occurred to me just from reading forums. I intend to get myself a pyrometer!

Because on a 30 second course you may be spending 6 seconds at the tire's limit and 24 seconds doing other things. It's those 6 seconds that matter when you're talking camber vs carcass temperature, not the other 24. Thus, you make the most out of when the tire is at its absolute limit, instead of trying to satisfy the overall tire carcass - because on the short course, it will always be faster that way.

Of course, on a road course, youll just melt the tire. AutoX wisdom only.