Anyone else have a problem w/ their vert shaking? Mine tends to shake between 55-60 mph and only does so when the top is down. I have inspected the rear suspension (feels like it's coming from there) and have found nothing. I recently put new tires on it and the problem hasnt changed. Any ideas? Thanks
Paul

 

only at 55-60 and not above?

 

It's not shaking, it's NVH (noise, vibration, harshness) from an off allignment. Having the top down magnifies it by like 10x.

A worn suspension (old swaybar & subframe end links, bad DTSS bushing, etc...) also tends to magnify it.

They didn't do this new.

 

yeah my verts got new suspension and i rode to cali with the top down doin 130+ didnt feel a thing. best drive ive had in a long time!

 

I had that problem too, only it was at about 40-50 mph. Turned out to be a loose front wheel bearing.

 

Yes, it only does it at those speeds on flat roads, but when i hit bumps it tends to shake a bit too (not the normal shake you'd expect, it's like it flicks the problem back on and then goes away shortly.) When i'm cruising at 70 mph on the highway it's fine. I think i'm going to check the wheels bearings now that you mentioned that joe-electro, thanks

 

Miatas tend to suffer from the "65mph shimmy". It's usually caused by wheels that are out of balance. This sounds like the same sort of thing. What's causing it in the Miatas is that the car is driving at the right speed so that the wheel vibration excites the chassis at its natural frequency, this has the effect of amplifying and adding all the little inputs to make one large vibration. You're probably not feeling it as much with the top up because it stiffens the chassis, which moves the natural frequency higher, above normal driving speeds.

When you got new tires how were they balanced. A high speed dynamic balance with roadforce is best.

 

Yeah get recomendations from several high end racing & exotic car shops, they can recommend an allignment shop that knows their stuff.