I could use some help here ? 1968 327. 8 yrs ago I installed new 8'' rally wheels and new 255 -60 goodyear GT II tires and was never happy, tire shop blamed it on excesive run out. Installed a set of my buddys new tires and alum rims off his 1980 vette and the car drove great. I recently purchased another new set of rallys from a made in USA distributor? and put new BFG 255 - 60 on the car, it's a lot better than the old ones but I encounter un- pleasant shake and wobble around 55mph under 50mph and over 60mph it clears up. I have read on a forum someone commented that the 68 wasn't design for 8'' wheels?
My suspension is a little stiffer than stock, new gas shocks and very recent alignment with no new parts recommended. All help is appreaciated greatly. Thanks

05/2020 It’s been a while but I wanted to follow up on my issues I found.

The drive line angel was out along with the transmission input shaft alignment. The corrections helped.

Installed 4 new rally wheels, after about 10 different wheels I finale got 4 that were in the .020 runout range.

Installed 4 new BF Goodrich tires with road force balancing, and another great improvement was felt.

Finally I had all 4 rotors balanced which made another great improvement! I no longer have any of the previously mentioned issues and the car runs down the round very smooth.



THX Mike

 

That's a classic description of having a tire/wheel out of balance. Guys have been running 8" wheels on these cars for years... Start by having the local tire shop check the balance of each wheel.

 

Thanks, I have heard of a few shops that balance on the car, any thoughts out there?

 

Yes, yes, yes, I know what you're talking about. Until recently I had the same problem. There is a lot of technical reasons about the big heavy tires but to shorten the story, I read about a method on another thread in this forum called Hunter Road Force balancing. It costs a little more but it really made a difference. Try it. Good luck.

 

I agree big time on the road force balance..its not done on the car but simulates a loaded tire. Then figures out if the tire has a pull or high and low spots etc..I can get a tire to almost 0 oz on the balance with it..I do find it odd that your buds car tires road good and the new ones don't..might want to get the same tires he has..and your right about the 8 inch wheel..the 68 had a 7 inch..but it really doesn't matter..wont effect ride..

 

I've had several sets of new BFG tires that were out of round and also had tread runout. It's next to impossible to balance that out.
Check the rims for runout, just as you would rotors. New ones should be very true. Next check the tires for runout and/or out of round. BFG should replace them, they have for others. They have admitted to faulty molds before. If no satisfaction, you can have them "trued" for runout or shaved for out of round. Once done, you will never ever experience a smoother ride.
Check the yellow pages and/or with local racers.

More often than not, it one of those situations where you will get a lot of until you can prove yourself a little more knowledgeable than the average customer.

 

I had them balance my 255 x 60 r15's progressive wheels and when they were done the ride was much better. They put some kind of stick on weights inside the wheel from inside of the bolt on flange area to the inside of the tire. He told me what they did but it was something like instead of "static" balancing he used something more like "dynamic" balancing in two dimensions instead of one. Sorry I can't explain it better but he said these huge rims and wide tires need a lot of balancing and the simple method does not work well.

Lance

 

You need to find a shop with the Hunter GSP9700 balancer or equivalent.

This slick piece of equipment balances all four wheel/tire assemblies and tells the operator of the equipment where to place all four individual tires to further minimize vibration and balance issues.


This operation will completely rule out the wheels/tires as the source of vibration.

 

possibilty of u joints, bent drive shaft

 

You need to have them Road Force Balanced . BFG 255s are not sold very often and often sit for years squished in odd places and positions. The only way to see if these tires can even be balanced is with a road force balancer.

 

good thought, all my shafts have new joints and where checked at shaft shop.

 

Thanks to all, off to google some local shops with force balancing, I'll re-post my out come.

 

Well it's been to three diferent shops no luck yet, last shop thought it was in the driveline, it seems like an enormous amout of wobble for driveline, vibration I can understand?