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Discussion Starter #1
Hi everyone,

Just recently got a hold of a 99 NB1 and I noticed that sometimes when I'm on the highway going 70-80 mph the car seems to shake while I'm driving. I can feel it & see it in the steering wheel and I can also feel it on my feet so it's not violent but it's certainly disconcerting. The car is somewhat modified (bought it this way)... has coilovers, and the prior owner removed the rear sway bar. Stock wheels and pretty new tires are on the car as well for context.

My plan of attack for it was to:
- Have the wheels roadforce balanced
- Then an alignment if that doesn't fix it

Does that sound like the right avenue? In my searching, it seems like the wheels could have thrown a weight or something so that's why I figured I would try that first (and it's cheaper).

Also, for the alignment... are there any specs that people can refer me to for someone who mostly drives on the street but does the occasional track day & auto-x event about 6-10 times a year? I found Dual Duty one one from SuperMiata (link) and that looks to fit the bill but just looking for advice around that:
- 4.5 ~ 5.25" front pinch weld height
- .06 ~ .18" rake (rear higher)
- Front camber: -2.5°
- Caster: +3.5 ~ 4.0°
- Front total toe: 0
- Rear camber : -2.0°
- Rear total toe: + 1/8", .06"

EDIT: Sorry for putting this in the wrong forum. I sent a request in just now to get it moved to Suspension.
 

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Definitely the wrong category but the balance and alignment is the right track. Do you have a hard top on the car? Ive noticed mine makes my car feel MUCH better at highway speeds when its on even with properly balanced wheels and an alignment. If the alignment and balance doesnt do it and a hard top isnt a choice lots of people swear by the GarageStar Derlin door bushings or Flyin Miata Frame rails as some of the cheapest ways to stiffen the chassis.
 

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Wheel balance is the problem 99% of the time. And/or wheel installation.

Get the wheels Road Force balanced and make sure you carefully install them back on the car if not using hub-centric wheels. A tiny bit of offset when torquing down the lug nuts will give you some highway shake.
 

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Discussion Starter #4
Definitely the wrong category but the balance and alignment is the right track. Do you have a hard top on the car? Ive noticed mine makes my car feel MUCH better at highway speeds when its on even with properly balanced wheels and an alignment. If the alignment and balance doesnt do it and a hard top isnt a choice lots of people swear by the GarageStar Derlin door bushings or Flyin Miata Frame rails as some of the cheapest ways to stiffen the chassis.
Wheel balance is the problem 99% of the time. And/or wheel installation.

Get the wheels Road Force balanced and make sure you carefully install them back on the car if not using hub-centric wheels. A tiny bit of offset when torquing down the lug nuts will give you some highway shake.
Thx for the input on the alignment & the wheel balancing. I am nearly due for inspection anyway so I may as well have the wheels balanced while it's there. Then if I need it, I will go back for an alignment too.

I did end up purchasing a hardtop for the car. I put that on there over the winter months to save wear & tear on the vinyl top. Figured also good for track days so why not. I will have to check out those other options to stiffen things up too.

I currently just have OEM 14" base model wheels on the car so I wouldn't think there should be any offset in the wheels but that's a good point that it could be. Certainly worth being careful for sure when I put them back on after I get them rebalanced.
 

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I actually have this issue on my 90 with hard top. It didn't always have this issue. I was told it could be a mixture of bushings and/or the suspension (everything is original never changed). Chassis has about 180k on it.

The shaking is actually so bad the steering wheel is really shaky anything over 60mph. When the road is smooth its not shaking.

Any ideas?
 

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I actually have this issue on my 90 with hard top. It didn't always have this issue. I was told it could be a mixture of bushings and/or the suspension (everything is original never changed). Chassis has about 180k on it.

The shaking is actually so bad the steering wheel is really shaky anything over 60mph. When the road is smooth its not shaking.

Any ideas?
This is a subjective answer but you should be saving for a rubber refresh. I would recommend checking not only all of the rubber suspension components (bushings, differential, control arms, etc) but also motor mounts and differential mounts.
 

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This is a subjective answer but you should be saving for a rubber refresh. I would recommend checking not only all of the rubber suspension components (bushings, differential, control arms, etc) but also motor mounts and differential mounts.
That was my consensus as well. I already have the money for it. Just want to make sure I am putting it in the right direction that will fix this issue.
 
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