Harsh ride

[DeeVeeEight]

1979 Corvette
New BP383 engine, new 5 speed TKX, driveshaft balanced, bellhousing indexed, runs and shifts beautifully.
New trailing arms (not rebuilt).
Rebuilt upper and lower control arms with Moog parts, all rubber, no poly parts. New sway bar bushings too.
Borgeson steering conversion.
Spreader bar, QA1 single valve shocks, VB & P monoleaf rear spring.
American racing Vector wheels (15 x 8) with Cooper Cobra radials. The wheels are old. Tires were purchased new in 2021.
At lower speeds, up to about 60 mph, the car rides nice. At higher speeds the vibrations start. The steering wheel, column, windows etc. all start to rattle and shake. I have had the wheels rebalanced 2-3 times. I suspect the older wheels may be part of the issue. I have checked the back sides and made sure that they are clean so that there is no debris throwing the balance off.
I would like to be able to drive the car at 80-90 mph and keep my teeth in my head.
Do I condemn the wheel/tire combination and get new ones or is there something I am overlooking? TIA

 

[phantomjock]

You mentioned the steering wheel... Any chance a problem with the box? How "new" is the Borgeson conversion. Bad box?
Might do a front to rear on the wheels/tires to elminate a possible bad one.

 

[DeeVeeEight]

You mentioned the steering wheel... Any chance a problem with the box? How "new" is the Borgeson conversion. Bad box?
Might do a front to rear on the wheels/tires to elminate a possible bad one.

The Borgeson box is about 2 weeks old. I am installing hub centric rings on the wheels tomorrow to try and eliminate that as a possibility. I'll also rotate the tires front to rear and see if that helps. Thanks.

 

[rtj]

Wheel alignment?

But, sounds more like a balance issue.

If you had someone close by you that could do a wheel swap for an hour or two, that would be the ticket.

 

[DeeVeeEight]

Close inspection reveals that my tires are out of round (flat spotted) due to sitting for too long. New tires are on the way.