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Wicked Wobble UPDATE 4/01/10

496truck

496truck

1/2 ton status
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Here's an odd tire wobble problem, (rig/tire info in the sig), the rear tires shake the whole truck at highway speed. Bad. If it was a slight vibration I could live with it. This is literally shaking the truck apart.

The tires are 33x12.5R15 Trxus M/Ts run at 28 psi on stock aluminum wheels. I'm running balance beads in the tires and have adjusted the weight up/down with no change.

Every lug nut has been hand torqued with a click type torque wrench to 100 lb.ft. To quote a movie, "It is 'dead on balls' accurate".

I've rotated the tires front/back and side/side with no change. Now, this leads me to believe it's NOT a tire issue cause whatever tire I put on the front, the steering wheel remains smooth and straight.

I've checked axle shaft runout (as best I could with a c-clip style axle shaft) with a magnetic base dial indicator with no real findings.

I've cleaned the mount flange on the axle shaft of any rust build up. Also cleaned the brake drums and backs of the wheels to remove any kind of rust or oxidation or other buildup.

So, what next? Is it the brake drums? Could they be warped or the mount surface messed up?

Could the G80 becausing this? Unlikely, it was in fine shape when I had the cover off recently. If you know of something I should look for, post up.

Tire pressure? Too high, too low? What does everyone else run 33s at?

I dunno. Reaching out for help on this one.
 
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Not balanced tires and underinflated tires can cause this. Bent rim? Bent axle?
I used to run my 33's at 35 psi
 
It's not a tire balance issue, already addressed that.
Not a bent rim/axle, already addressed that.

Will try upping the tire pressure next. 35 seems a bit high, like the tire would only ride in the middle of the tread. I'll try 32 psi first.
 
Have someone follow you in another vehicle to watch for any obvious issues??

I've driven near people on the road with a bent wheel or a shock that was completely blown out and was amazed at the amount of motion that can be seen at highway speeds.

Sounds like your issue is dramatic enough that someone knowledgeable in a chase car could quickly diagnose it.


:usaflag:
 
Ya know, I thought about doing that. But my wife is scared to drive it on the highway like that. I'd be the one to figure out what's going on. I did try putting it on jackstands and driving it up to 60 to see but it wasn't showing any signs of this happening.

Guess I need to find a brave friend to whip this thing up the highway.
 
Keep in mind we're talking rear axle here. I did check for play in the rear axle shafts while the drums were off. And the seals are good. Rear brakes are new except for the drums. Other than that, I did not pull the axle shafts, just changed out the fluid.
 
UPDATE

After checking everything I could, I started looking at the tires again. Figuring the balance beads just weren't cutting it and seeing that I had alloy wheels that would not accept wheel weights, I ordered up a set of cheapo steel 15x8 white waggy wheels. Swapped the tires over (vacuumed out the balance beads) at work and balanced them up as best I could with the weights we have there. Put em on the truck and took it for a blast down the highway...

What a HUGE difference. It now runs almost smooth at 70ish MPH where before it would shake the whole truck anywhere over 50. I could prob get it perfect with another helping of balance beads but I'll deal with that later, for now it's about as good as I would expect with these tires.

For anyone having a similar issue, I would suggest doing some reading at the Innovative Balancing website. http://www.innovativebalancing.com/ The FAQs and How It Works were very helpful.
 
No. The old wheels were straight. The tires had severe lateral imbalance which can not be corrected with balance beads.
 
Been there, tried that. The brake caliper was scraping them off. Plus they don't like to stay on for long after wheeling trips. Steel wheels and clip on weights were the simple solution.
 
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