Originally Posted by JPalmer
Thanks guys! I am hoping that it is the tires. I looked up that brand and they cost about $105 each, which gave me pause as load range E tires I have on my dually and the missus's 2500 suburban are over $200 each.
Do you think rotating the tires on the rim 90* then re-balance them would help?
No, but it's worth a try simply because it costs nearly nothing. I'd bet on the problem being balancing more than rotating the tire on the rim - but both cost nothing.
But the only way that rotating the tire on the rim will help is if the rim AND the tire were both manufactured to be out of round or out of plane (fore & aft) or don't have their mass distributed evenly.... and that somehow the mounting guy go unlucky and lined one of the wheels & tires up just "exactly right to be wrong". All of those things are possible, but not likely.
I'd say it's more probable that the wheels are good and it is the tires are either not manufactured round, or are separating internally, or the balancing was done wrong.
You might want to simply have the tire guy jack up the front and spin the tires up to eyeball them first - ask him if he has the machine to do that - it's just a motor and a friction drive mounted on a floor jack. If he can do that, it is done with the front jacked up while leaving the tire on the vehicle. Just watching the tire and feeling the steering wheel while that goes on often tells you something, but if the fronts do start to jump around at some speed you still won't know if it is due to the tire/wheel/balance/bearing or if you just hit a resonance point in the suspension spring and damper system.
Sometimes you can balance it out the motion by just changing the wheel weights right then, but more often you will end up taking the mounted tire off of the vehicle and putting wheel and all on the balance machine to get it to balance right. THEN you can put it back on the RV and spin it up mounted and see things if things are stable.
Having had a mechanical shop for years, I've seen this sort of thing. It's a problem to get it right. And often it involves getting the tire shop to take the tires back and try a different set.
I'm sure you know that if you want to deal with this the right way you have need a real mechanic instead of guessing along with a tire guy busting tires for minimum wage. Sounds like you are still at the "working with the tire guy stage", so I'm trying to help you out with what you both should be looking for.
The real mechanic was once a tire guy himself, and learned to start at the wheel bearing and then move on outwards, satisfying himself at each step that everything is round and running in plane. The balancing is just the finishing touch.