Brian,
I have a 93 miata that starts to shimmy around 60 mph. Depending on the road conditions it can get quite annoying. Dennstedts installed some frame bracing, and I had a wheel balance and alignment done.
I have stock 14 inch alloy wheels with Toyo T1S and KYB 8 way set on position 2 which is supposed to be same as stock.
Although this helped somewhat, the car will still shimmy under certain conditions.
Eventually, I would like to do track events with this car when I get everything ironed out.
Any help would be appreciated.
Bert
Cardiff, CA
65 mph shimmy...HELP!
Hi Bert,
All cars have a natural frequency at which they vibrate/resonate. A convertible is less stiff than a hardtop and will have more of this than other cars. Many things can make this worse in a Miata....age alone being one of them. Alignment. One tire is out of round or out of balance. Too much unsprung weight makes this worse.
As for your car, your wheels and tires are light and the braces all help by raising the frequency in an aging miata. A roll bar is the ultimate brace and would help even more and since you plan track days anyway, I would do a four point roll bar next if you have not done so. I also would take another look around the suspension for worn parts. Larry has done all the classic first steps to fixing this but if Larry has not done so yet, tell him the problem continues and have him check the health of your bushings, control arms, etc. Worn or bent suspension parts could still lurk in there if he has not actually done a search for such. Also, add any additional braces you have not already done...
All cars have a natural frequency at which they vibrate/resonate. A convertible is less stiff than a hardtop and will have more of this than other cars. Many things can make this worse in a Miata....age alone being one of them. Alignment. One tire is out of round or out of balance. Too much unsprung weight makes this worse.
As for your car, your wheels and tires are light and the braces all help by raising the frequency in an aging miata. A roll bar is the ultimate brace and would help even more and since you plan track days anyway, I would do a four point roll bar next if you have not done so. I also would take another look around the suspension for worn parts. Larry has done all the classic first steps to fixing this but if Larry has not done so yet, tell him the problem continues and have him check the health of your bushings, control arms, etc. Worn or bent suspension parts could still lurk in there if he has not actually done a search for such. Also, add any additional braces you have not already done...
Brian Goodwin
Good-Win Racing
www.good-win-racing.com
Good-Win Racing
www.good-win-racing.com
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sloopercat
- Posts: 242
- Joined: Sat Feb 18, 2006 7:26 am
You also might try a balance use a Hunter GSP9500 road force balancer. They can make them a lot better than a std spin balance. My '90 NA had a tower brace, a lower front suspension brace, a Canon clone rear brace and a 94 cockpit brace. It still would shimmy a little bit at certain speeds, but much much much better than where I started from. On the T1's tires you might try 28-29psi, that made mine a whole lot better, even with all the above it shimmied if the tire pressures were too high.