Just got my 96 Miata on the road.I had never drove it before putting new tires on it.So I go drive it for the first time today and at about 60 she is shaking and I mean shaking.Jacked it up and nothing loose.Wheels,spendles,or U joints.I watched the guy bal. the tires any ideas? Oh and I tried it up to 80 and no change just got worse.
The obvious question is who balanced the tires? Are you sure they knew what they were doing?
They're VERY sensitive to wheel balancing.
There's a special balancer that people say you should try to seek out, i forgot the name at the moment though.
But yours sounds like it could be worse. Sure you don't have a damaged tire?
Many Miatas have a speed wobble around 55MPH, due to tires that aren't quite balanced. However, it sounds like yours are way out, as the 55 shimmy should go away just above or below that speed. Take it back and have the balance checked. If you can tell where it is coming from (or can't tell), try rotating tires to isolate it.
Its so bad theres more than one if its tires.but the guy speed bal. them on a Coats bal.
92CelicaHalfTrac wrote: They're VERY sensitive to wheel balancing. There's a special balancer that people say you should try to seek out, i forgot the name at the moment though.
A Hunter road force balancer.
How long has the car been sitting? Prolonged sitting and/or cold weather can cause a temporary flat spot in a tire making it feel like crap until you've driven it for a while.
I can vouch for the 55mph shimmy.. Mine shimmys with the summer setup (autocross flatspots and at least one rim slightly bent) Goes away when the snow tires are put on though.
It has set for 2 weeks before I got to drive it but the tries are new and today was a warm Florida day.As for the 55 not bad at 55 but at 60 ....
Mine is worst at 60mph. I didn't have my wheels/tires balanced on a Hunter. Will have to try that this summer.
it can vary by that much.. the question is, does it dissappear at about 5 over/under the shimmy speed for the most part?
The cars just seem to have a natural frequency right around that speed on the wheels that can build into a whole car shimmy.
Do some searching on Miata.net and you will read more then you ever wanted to know.
In essence, a small thing builds into a big shimmy at that specific frequency. Gotta just hunt out the small things if you gotta get it gone.
There are many many many bushings in the Miata suspension. Maybe yours are really worn and are exacerbating the shimmy issue. A bad joint in the driveshaft will also do what you are describing.
I have had a case of bad balances recently... Even from a good shop...
Took them to a buddy... Problem solved. A good rebalance would be the first thing I would do.
The whole reason I left the 14" tires was so they could help absorb some of the ride.I avoided the larger wheels for this reason.Josh I checked the bushings and they honestly look good.I can tell the difference between a Ujoint and tire and this is suspension but the new tires thru me off.I'm going to take it back tomorrow so they can re bal. the tires.
A bent rim can cause similar symptoms. Balance issues usually will go away if you go faster. A bent rim, usually just gets worse.
speedbiu wrote: Its so bad theres more than one if its tires.but the guy speed bal. them on a Coats bal.
I can balance a tire, take the wheel off the machine, put it right back on, and show a significant imbalance again. Operator error is very easy, and 90% of it is putting the wheel on the machine in the first place.
Stock wheels? Or aftermarket? The wheels are hubcentric - make sure that the diameters are the same from the wheel to the hub, and if there are spacers (often there are on aftermarket wheels), make sure none are missing in the wheels. I had this problem recently with a MKII MR2...
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