16.00 tire life

[Lonnie]

I think one of the modes of vibration is rocking of the axles through the pivot. In this mode the tires are acting as springs, and the entire assembly is rocking as a spring-mass-damper system, with, as noted, probably not a lot of damping. This system has similar characteristics across the pivot point, i.e. similar axles and tires on the two rear axles. When this this assembly gets to rocking, the motion tends to be perpetuating since the reaction of one tire feeds into the reaction of the other. When trying to suppress vibration in a symetrical system, one tactic is to introduce some sort of asymetry. So for my M925A1 with the 14.00R20 Goodyear AT-2As, I run different pressures on the rear two axles, say 45 front and 35 rear, and I think this has helped. I would be interested if anyone else sees any improvement from doing this.

I thought about that yesterday. The engineer in me gets some crazy ideas sometime, but never got the opportunity to try out. I'll give it a shot & let you know.

 

[Julian]

The down side of different pressures is that because of the pivot, both mid and rear axle hold up the same weight. If they have different pressures they will have different radii and thus introduce scrubbing. Ideally, the exact center of all driving axles should be exactly the same height from the road. This is called the static loaded radius. The idea is the there is only one correct static loaded radius and the air pressure should be adjusted to achieve this. Heavy loads need a lot of pressure, light loads don't need so much. It gets complicated when best tire wear may have a different design static loaded radius from some other tire parameter- like best rain performance. Adding damping would help.