Posted by Bob Stopka in PCB [68.35.243.55] on Monday, May 13, 2013 at 23:16:47 :
In Reply to: WM300 Shimmy? posted by Sterling From TX [99.98.76.231] on Saturday, May 11, 2013 at 21:59:54 :
Just went through this with a WM300 that had 20 year old 900x16 NDT's that looked ok except for minor weather check cracks on the side wall. 35 mph it would always shimmy bad. Death Wobble. It was the left front tire causing it. The tire tread around it was evenly worn BUT instead of being round the tire was slightly oval. Tire shop found the issue. Jack up the front end, and take an oil can and place it on the floor under one of the front tires.Let the jack down until the tip of the oil can spout almost touches the tire center portion of the tread. Spin the tire and by eye see if the space between the oil can and the tread is basically the same spacing as the tire spins. you can also check the inner and outer side walls by putting any strait edge close the each sidewall and observing the spacing as you spin the tire. These are old mechanics tricks that a 70 year old certified mechanic friend told me. It's just a quick check and by no means scientific, but it will give you an idea. If you find an issue take that tire and reverse it with one off the back of the truck, but be sure to do the same test on the tire you are going to use as the test tire. Whether the tires are old or new you still could have a tire issue. Start with the simple stuff first. I had that problem once and it turned out to be that the 4 bolts that tighten down the pittman arm casting on the top of the knuckle had become somewhat loose. Once it retightened those 4 bolts the issue went away.