Ok I think I understand, your wheels have a bore of 87.1. Discount Tire can have custom rings to convert your wheels from 87.1mm to a 71.5mm. I do not know if it would solve your issue, but having the wheels properly centered around the hub would sure help.

I just think it is weird that you have the same issue on 2 set of tires using the same wheels.

 

It feels like a different issue. The GY's had a definite speed specific vibration that just felt like an old school "tire out of balance vibration" if that makes any sense. The BFG's don't have the same vibration. This starts about 40 mph and continues to strengthen up to 80 mph. It seems to get stronger and weaker....ungulating if you will. I have been very frustrated with the whole thing. thanks for the feedback.

 

As a Mechanic, I would approach this problem your describing two ways. First, you need to rule out your front end. This can be done by raising the vehicle on a lift, engine running in 4wd (provided your vehicle has 4wd). Look (or have someone look) for bent wheels, broken belts/bands (internal tire defect), or anything out of the ordinary while tires are spinning. Note: if only one wheel wants to spin, from park, someone can hold the wheel that wants to spin, in order to force opposite wheel to turn. If all is well (or vehicle is 2wd)...

Second, watch (this is were protective hoods or covers get in the way) the spinning tire (no weights) on the balancer. It is possible to perfectly machine balance a bent wheel.

I would avoid full-time tire shops that let the "need for speed" to overlook properly balancing large tire sizes. Remember, they need quantity not quality to make a living. I routinely mount and balance all types of aggressive off-road tires up to 37" with no shimmy or vibration. Hub-centric or lug-centric makes no difference, in my experience.

Man, all my post's are long-winded!

 

I appreciate the suggestions. The guy who balanced the tires took his time and even rebalanced the spare to make it better. I will take a look at the front end.

 

Have you gotten the rings yet, did they help at all?

 

Yes, I got them. I do think that they improved the ride, but did not eliminate the vibration at 60+ mph.

 

I agree. I have had no problems with my Duratracs. I drove another JK with KM2 and they are fine. I balanced Boggers on bent up steelies on my XJ and they didnt wobble that much until after 70mph lol.

Might want to have the shop run a wheel on the machine without the tire and see if it is machined properly and not wobbly.