Deerkiller

Hey guys, I was driving my Miata back from work today and noticed that there was a vibration at higher speeds. Around 55-60 MPH on the highway. The first thing I am thinking is a drive line with bad u-joints. So I climbed underneath it and grabbed the drive line. When I attempted to rotated the drive line it seemed to be be a little bit of play. Now when the car is in gear should I be able to turn the drive shaft a little bit or should there be no play in it what so ever? I am trying to remember how a bad u-joint should react when I let off the gas and then accelerate again. Now I did check all 4 wheels to make sure that everything is tight and they were. I did grab the rear half shafts and they seemed all tight too. Any help on the matter would be great.

Thanks.

RedTurboMiata

may want to give this a read the 65 shimmy, these cars are notorious for having a shimmy, mine starts at around 55 and stops around 75. http://www.miata.net/garage/65_mph.html

Deerkiller

Very interesting read. I will have to take off the locking lug nuts and get them replaced. I will also have to see if the local Les Schwab has this more precise wheel balance machine. Thanks for the heads up Red.

RedTurboMiata

np, its not going to fix all of the vibration but should help. there is a bit in the chassis if i remember from my reading on the subject

Track

From my understand, it seems to be a resonance frequency of the chassis. Not much you can do about it. Even with a Hunter balance machine it doesn't go away, as much techs don't have to get the force balance below 20.

I have learned to live with it, but unfortunately as you get stiffer springs, the vibration gets worse. Best thing to do is cage the car

RedTurboMiata

you will get used to it after a while.if you want to keep the security lug nuts. move to all of something like this http://www.summitracing.com/search/D.../?autoview=SKU

curly

Keep in mind I use the same security lugs on all 4 studs, but when I got rid of the daises a lot of vibration went away.

flying_solo

iTrader: (1)

I have the shimmy. It moved a bit with the FM Frame Rails and the roll bar towards 65. So, I drive 60 or 70 unless I want the vibration.

TL;DR Drive harder and you won't notice.

Dntlift

Fwiw, I got my car with bossfrog rollbar, and bbs wheels. I never EVER have had this shimmy that so many have experienced. I dont know why, but my guess is the rollbar.

RedTurboMiata

if you get bored one day take it out and drive around, bet you get it then