Wind buffeting?
Drifting
Joined: Jun 2020
Posts: 1,355
Likes: 396
From: Northwest Ohio
I would guess wheels/tires are the cause plus the reduction in torsional rigidity with the targa off. You must be hitting a resonance.
Mine with the top off does not do this but you can tell there is extra flex over bumps etc…
Mine with the top off does not do this but you can tell there is extra flex over bumps etc…
Drifting
Joined: Jun 2020
Posts: 1,355
Likes: 396
From: Northwest Ohio
...
I've put 400 miles on it so far driving over 50MPH most of the time, usually averaging 60MPH. I also ran it a bit over 90 for a minute on a very long overpass once. Until the top came off today, the car was smooth on smooth roads, no indication of out of balance tires or out of round wheels at any speed. The car does feel unstable over bumps at any speed as-is, but I never saw any actual flex in the front end before, and I never felt like the car was shaking apart. I was under the impression removing the Targa top did not affect torsional rigidity at all. I stand corrected. Maybe the shocks are so far gone, and/or the springs are too, and that all came together with "a little extra flex" to really compound the issue. Top is back on and will stay on for now. Thank you.
..
I've put 400 miles on it so far driving over 50MPH most of the time, usually averaging 60MPH. I also ran it a bit over 90 for a minute on a very long overpass once. Until the top came off today, the car was smooth on smooth roads, no indication of out of balance tires or out of round wheels at any speed. The car does feel unstable over bumps at any speed as-is, but I never saw any actual flex in the front end before, and I never felt like the car was shaking apart. I was under the impression removing the Targa top did not affect torsional rigidity at all. I stand corrected. Maybe the shocks are so far gone, and/or the springs are too, and that all came together with "a little extra flex" to really compound the issue. Top is back on and will stay on for now. Thank you.
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You said that the car feels "unsettled" over bumps and perhaps has suspension or wheel related issues, I would start there and ignore the cowl shake for now. Get it handling properly first then if the open top issues are still present and it's bothering you address those. good luck
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Race Director
Joined: Oct 2012
Posts: 17,382
Likes: 6,525
From: Melbourne, FL
A gew things to look at.
New bushings... which ones? The control arm bushi gs are a real.pain in the ***, and so many people don't do them. They could have just been sway bar bushings and called it a day, like most people. I did them on my 92 at roughly 130k and had a mix of "barely a bushing" and "looks basocally new". I painstakingly did a prothane kit woth poly bushings and they were a huge improvement. Kick the tires and look for movement, or lift the car and do it the right way.
Shocks. Definitely possible. You can do a real quick test by shoving each corner of the suspension down.
Alignment. Get one done. I'd probably do this after ruling out the bushings, because you'll need an alignment after doing them, but definitely get one, it could easily cause this issue.
New bushings... which ones? The control arm bushi gs are a real.pain in the ***, and so many people don't do them. They could have just been sway bar bushings and called it a day, like most people. I did them on my 92 at roughly 130k and had a mix of "barely a bushing" and "looks basocally new". I painstakingly did a prothane kit woth poly bushings and they were a huge improvement. Kick the tires and look for movement, or lift the car and do it the right way.
Shocks. Definitely possible. You can do a real quick test by shoving each corner of the suspension down.
Alignment. Get one done. I'd probably do this after ruling out the bushings, because you'll need an alignment after doing them, but definitely get one, it could easily cause this issue.
