Rear shimmy at 50+mph

dalmationlovers wrote:
Have a question for the experts out there. This weekend was the first extended trip after I installed my value extenders and was finally able to adjust all the air pressure. 03 Chateau Sport 26Q, 8.1 Vortec with 480L tranny. Set the duals at 80lbs (max) and the fronts at 75 lbs with 80 as the max. Weigh about 11,500 fully loaded.

The rears before were at 90 lbs and the short trips I took I didn't notice any shacking or shimmy. Friday and Today, each way about 2.5 hours time, while traveling to and from the campground the shimmy was bad. No issue with the front tires and would only begin above 50 mph. I was thinking that my duals are out of balance. Just need some ideas.

Thanks
Arnold

At first blush it looks like you have too much air in your tires for that weight. I'm thinking more like 65-70 PSI max....probably closer to the 65 end. Pressures should be set when tires are cold (not driven on). Not sure what your tires are rated for but 90 sounds like way too much air. You will need to get the wheels/tires looked at. Your could have a tire fixing to let go in the worst case.