I have a 2000 Buick Regal. It has close to 100k miles and runs well, and has been well maintained. I have a vibration that seems to come from the front although it’s hard to tell .It occurs around 35to 45mph then again around 75mph. I know that it’s not balancing and it happens regardless of what gear you’re in. Any ideas?
I had an 88 Chevy Beretta that had the same problem. Putting new tires on the car solved the problem. The tires (Eagle GT+4) had about 45k, but had another 5 or 6k of tread left before I replaced them. How old and how many miles are on your tires?
Ed B.
I know that it’s not balancing
Famous last words. 
How about telling us why you don’t think it is balancing.
I would also suggest checking for slipped belt or other tyre damage and or rim out of round or other damage.
tires are Kumo all season. They have about 25k mi. now and they have been rebalanced.
It could be a loose suspension part; generally a loose tie rod or tie rod end.
A loose wheel bearing could also cause it.
You seem to be pretty optimistic that the wheel balance could not be at fault, but I would not dismiss that possbility.
Just because they’ve been rebalanced does not make them correct.
Wheel balancers can sometimes be off the mark and do need calibration now and then.
I used to work for a dealer who purchased a new Snap-On wheel balancer and that thing was nothing but a boat anchor from day one. It was horribly inaccurate in spite of Snap-On’s protests that it was dead on the money.
When a brand new spare tire out of a brand new car is spun up 3 times and 3 different readings are given varying from 11 to 17 ounces out, it is not to be trusted. The only way a new tire could be this far out is if it had a brick inside of it.
Another possibility would be if you have wheel covers, especially wire ones. The wheel covers can be out of balance and once reinstalled on a perfectly balanced wheel/tire may throw it out of whack.
Are the tires wearing properly or are they starting to wear funny? If wearing funny, check the front end alignment and the bearings and bushings. Any easy way to check is to jack up that wheel so it doesn’t touch the ground (do this safely, please). Then pull the bottom of the tire out to the side. If you can wiggle it that way, then you have suspension components that have worn and need replacing.