Twitchy Miata NA

I have a 94 Miata. I added TEIN coilovers and wheels with 205 Yokohama tires. Had the car aligned (twice). Now the car is twitchy, darty going down the road. Drove well before the changes. The old original shocks and springs were worn out but smooth. Now the car changes lanes if you sneeze, "hunts" around the lane, requires constant input and correction. Did we miss some alignment setting, am I paranoid, is this a characteristic of the shock, spring, tire, power steering combination. Car handles curves ok, it's just darty.

What are your alignment settings?

Wheel offset? More scrub radius can do that.

How wide are your wheels?

Toe out in the front will also make it twitchy.

Did you change the wheels and tires out at the same time as the suspension and alignment?

Alignment settings can make a massive difference on a Miata, what did you get it aligned for? Street driving? Auto-X? Track?

I'm guessing it's in your alignment settings, probably toe, but without knowing the numbers it's impossible to make a diagnoses. Knowing the wheel width, offset and tire type would also help.

Did you replace any bushings, alignment bolts or ball joints while you were in there?

Is it all the time or dependant on temp? My Miata started getting squirrely about a month ago. Took me a while to realize it was happening when below 50 outside. My Dunlops just don't like the cold weather.

My Miatas were both really sensitive to tire pressures. You might want to check for a low tire if you've not done so recently.

Did your new coil-overs come with alignment plates that let you significantly increase caster?

Sky_Render wrote: Did your new coil-overs come with alignment plates that let you significantly increase caster?

Does not apply to the Miata's double wishbone suspension, that's a strut thing.

I also want to know more details. Wheel offset and alignment are the two big ones.

trucke wrote: Toe out in the front will also make it twitchy.

This

Finally I can access the forum again.... The wheels are Chaparral 15x7 with a 38mm offset. 205-50 Yokohama Sdrive tires. The alignment was set to stock according to the shop that did the work. The suspension work was first, tires and wheels were added a couple of weeks later. I had hoped there was a magic bullet like tune the radio all the way to the right, blow the horn twice, etc. Failing that I plan to:

1. double check tire pressures and experiment a little with them. 1a. change back to stock wheels and tires to compare.

2. explore changing the alignment, particularly toe in/out

3. Either live with it or do what I started to do (and chickened out) to begin with and call Keith and have him send me whatever he thinks I need from FM. I am less than thrilled with how the TEINs turned out and if I had to do it over I would go FM as the supplier.

Note to Stampie: Outside temp seems to have no effect. Today is about 65 and no change.

If you've got a printout of the "stock" alignment, post it here or email me directly. Miata owners tend to have a different view of an acceptable alignment than a lot of the motoring public, and you can be fairly screwed up but still in the range of stock tolerance.

Wheels and tires are good, I wouldn't be worried about that. Run about 30 psi.

Keith, I do not have the numbers on the alignment (that I can find). Tell me what you recommend and I will go have that put on the car. YOU ARE THE MAN.

Mark

Street car recommendations. Make sure the alignment shop knows you're looking for more than "it tracks straight" and see if you can schedule it for a quiet time in their shop. Our local guys are hopping on Monday and Friday, so I always schedule midweek. This will follow really deep truck ruts somewhat but should be good.
https://www.flyinmiata.com/tech/alignment.php

What sort of shop did the alignment? If it was the local Kwak Fit, go to a shop that the local Auto-X guys use. They can probably align Miatas in their sleep and will most likely do a good job rather than a good enough job.

I have had decent luck with even normal shops if you bring them the settings you want first. I usually let the counter guy know that I will want his printout after to compare to my request before I accept the car back.

Without a printout you might as well consider it not aligned at all. Always insist on a printout. You can check the car yourself (tons of Internet tutorials) that will at least tell you if it is way out. Once upon a time I used jack stands and string. I have basic alignment tools now so much easier.

My guess also would be on the alignment being off.

Tom

The alignment was done by a top notch local shop, Pete's Alignment, that I have used many times in the past and will again. I had a printout of the alignment but it's misplaced, misfiled, lost, or something.

Yeah I know about misplaced printouts........I just had hunt the one for the Datsun.

Since you have a good local shop I'd use the settings Keith gave and go with it.

You might cash those Teins in for some Konis and quality lowering springs. Your corner weights could be all over the place.

I hate the threads that fade in obscurity and leave you unsure of the outcome, so here's what happened: First I adjusted all four tires to 28psi. This exposed one problem. The gauge I often used was reading 5psi short of the three gauges I check it against (why did I have 4 gauges? question for another day). I chucked the offending gauge in the trash. Then I took the Miata for an alignment and gave the tech the settings that Keith had pointed me to and I had printed out.

Result: Twitchiness is gone, the car tracks much better, a much better driving vehicle.

Thanks to everyone for their input.

Mark

Did they give you a before/after printout? It would be interesting to see the before numbers...

No before printout. But toe on front was off, one in,one out.