Rough Ride

Your original shocks died at least 50k miles ago. New shocks will help keep you off the bumpstops and improve the ride.

The same thing happened with my '91 at 99k. I went to have the tires balanced and the techs noticed I had a slightly bent rim. Replaced the rim and the world was good!

DonB

Koni or KYB AGX adjustables. You may spend a little more on parts, but you'll never have to replace them again. Many dealers charge NINE HOURS labor to replace Miata shocks, though $250 or so is reasonable (plus parts).

What? When I was in the Miata club, a local amateur here did it in front of my eyes in a couple of hours. Including replacing springs. IIRC, it was the first time he did it.

Leon

The "book" says 9 hours, so they charge 9 hours. It's got nothing to do with how long it takes. I don't how long it actually does take them, but the official procedure requires a

Even the independant garage I got a quote from said 9 hours labor to do 4 shocks on a Miata.

I did mine myself, and it took probably 8-10 hours. It was the first time I'd done that job and a scewed a couple things up and had to re-do them. If I did it again and had access to pneumatic tools and a lift, it would probably take less that half that.

I replaced the front shocks on my fiancée's 93 Miata last weekend. The first shock took 2 and a half hours (learning curve) and the second only took an hour. Tomorrow I replace the rear shocks and only plan on two hours.

You're shocks are long past dead but also have your wheels checked. The BBS wheels are beautiful but aren't the strongest wheel they ever put on a car. It doesn't take much to take one out of true and it doesn't need to be much to show up on a Miata.

Tom

Hobart wrote:

Ok, Hobart, let's think about this a bit more. You're trying to describe the problem but the terms seem to be mixed. "Rough ride" and "unbalanced" and "imperfections in road" are three different things.

- Does the car wander in the lane? Perhaps you have loose tie rods.

- Does it seem to pull from one side of the lane to another, following imperfections? Many tires, particularly high performance tires, have this "tramline" effect where they follow imperfections in the lane.

- Does the car shake, particularly at around 60 MPH? Unbalanced tires or worn out shocks might be the problem.

- If you're "feeling imperfections on the road, in the steering wheel, particularly on rough roads," perhaps it's the normal, fairly stiff, ride of the car?

Your tires are out of balance. If it started suddenly, it's possible that you lost one of the balancing weights, which is fairly common. The shop guy needs to balance them again.

Sometimes it helps to ask for a "high speed" balance, or to "spin them twice" (i.e. spin up the tires on the balancing machine again after they put on the weights to verify that they're on properly--normally they don't do that in most shops). Mention to him that the Miata is known to be very senstive to wheel balance. Take him for a ride to show him.

Good luck.

Have you tried swapping the tires front to back to see if still feels like it is the front end?

-- marcio at compudimensions.com

If this started when you replaced the tires, I'll bet the problem is the tires themselves.

The Miata is known for having a vibration between 50 and 70 MPH. It is worse on rough roads My experience is that and that some tire brands shake much more than others. The stock Michelin's on my 2000 shook at 57 MPH and it went away when I switched to Dunlops.

Sorry to have to suggest this....

Randy

The Miata tires need to be balanced very carefully since it is a light, not very stiff car. I would have tried the second balance at another shop, to be sure it was not just tolerances. There is some info in the garage section of miata.net.

Also note that some tires have a pronounced stiff spot where the tires are joined, which will also cause vibration peaking at 65 mph. There is no cure except playing with tire pressure.

Out-of balance of other moving parts (brake disks?) could also cause the vibration, but the sudden onset seems to be inconsistent. If I had to bet, I would probably bet that Douglas is right and that a weight fell off of the wheels, and that the new balance is not that accurate or the new tires have a problem. Of course, I might well be wide off the mark, as usual. ;)

Good. I have the M-wheels myself and they *are* soft. I had to have them fixed twice, too expensive to buy new if you can help it.

Doubtful if it peaks in the 50-70 mph range, if you ask me. Leon