Posted by Greg Coffin [172.68.26.205] on Monday, September 16, 2024 at 15:26:20 :
In Reply to: Wheel Balance? posted by Torvald [172.68.23.54] on Friday, September 13, 2024 at 00:49:29 :
I have a couple thoughts on the tire issue, so bear with me here. I run stainless balancing beads in my 6x6 and M37 (9.00-16 bias ply) and I really like them.
Without getting too much in the weeds, I think your issue is the change in tire pressure, and the balancing beads may have masked the issue on the back axle. Let me explain (enter the weeds).
A tire can be balanced and still be a bit out-of-round. When the tires were first mounted on the rear axle they wore in over time at the given air pressure and ran smoothly after 3-400 miles, and the balancing beads helped mask the minor out-of-round condition at the beginning, and the tires wore into a more-round shape over time. You may not have noticed the "out-of-roundness" as much being on the back axle. Also, the wheel wore in on a certain part of the tire, given the specific tire pressure. Everything felt good.
Moving the tires to the front axle may have made their "out-of-roundness" more noticeable through the steering wheel. And increasing the air pressure caused the tires to contact the road in a different area than before, which might be more out of round than the previous wear pattern. After 3-400 miles the tires wore in smoothly due to the balancing beads, which is why they feel good now.
I think the intermittent nature of the vibration confirms my thinking. I have the same issue on my 1962 WM300. At about 35mph the front end starts to wobble a bit, then it stops and reappears after a minute or less. It doesn't happen above 45mph. The truck does not have balancing beads in the tires. My guess is that both tires are slightly out of round, and they are slightly different diameters, so the "out-of-roundness" is either in sync or out of sync between the tires, and I notice it more or less depending. The wobble at 35 matches the resonant frequency of the front axle and they reinforce each other, but not at 45mph or faster. I'll bet my tires are heavier than yours, which lowers the resonant frequency.
How's that for some weeds!
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