Well I decided to take the 36's off today. They don't work for me. Everything was fine when I put them on. I got an alignment and had them all balanced. The guy told me he thought that one was a little bent because it took a bunch of weight but I didn't really give it much thought because it drove okay. Now today I was back to working because the weather is finally warming up. It seemed to handle the weight just fine aside from the 3.12:1 effective gear ratio everything seemed okay. Then it came time to add more weight. I had 12 scaffold frames strapped to the headache rack besides other things and I took off down the road. Everytime I'd hit a little wavy section of road the whole truck would start this uncontrollable bouncing. I think it is a combination of frame flex and the big tires with 30lbs of air in them acting like a spring board. I have never seen anything like it. I thought I was going to break something it bounced so hard. The only way to stop it was to slow almost to a stop. I guess this was never an issue previously because the rock hard 65 psi tires never had the give in them. I always thought that the frames in these trucks looked weak, now I know.

 

I had the same exact issue with the 01 superduty I used to have when I was running 39's thought the truck was gonna come apart it shook so bad.I put on dual ened to end stablizers and new ball joints and never had the prob again.But I still reall dont know what caused it.

 

I have ran 35s, 36s, 38.5s, and 40s, on one of my trucks with six-inch suspension-lift, hauling heavy gooseneck loads of cattle cross-country.

Honestly, the truck handled and drove way better with the large tires than it did with normal tires.

Of course, I never ran anything except NYLON BIAS tires, no radials, so I did not have the flimsy sidewall flex to deal with.

I tend to think that you may have some suspension issues that haven't showed themselves, until you added the taller tires and made them more noticeable.

Have you checked your shocks, steering-stabilizers, sway-bars, etc.??

Weak shocks can cause the uncontrollable bouncing you are experiencing, due to the added UN-SPRUNG weight of the larger tires being harder to dampen suspension oscillations.

Check it all out and let us know what you find.

 

I agree. I tow and haul heavy with 36's and no problems. When I bought the truck I replaced the shocks, steering stabilizers, and drag link because all were worn. Do a complete front end shakedown, and check all shocks for damping. Good luck.