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Even though this thread is already aging, I would like to add some comments to it. It is one of the better subjective discussions of tires that I have ever seen in that it contains fairly wide ranging ideas. I think it will make a good future reference source for RV_NET readers.
I know that it is a common belief that tires worn on both the outer edges are
always always caused by under-inflation. I would like to question that.
I had recently been researching dual tire pressure equalization systems whereby the dually tire valves are connected together so that each inflates at the same time from one valve port. I seemed to have run across a related wear issue in this.
I read one or more opinions that dually mounted tires will wear unevenly when they are not inflated equally. One of the info sites was
http://www.stengelbros.com/truck-and-wheel-parts/cat-eye-tire-pressure-system/. The claim here is that the under-inflated smaller tire will wear more because the larger full tire will "drag" it a bit. A detailed Case Study by Bridgestone is cited.
The thing is, that if that is true, and a single, non-driven tire is over-inflated and the center tread is larger (bulged), shouldn't the main center tread, which certainly has the most traction, also logically drag the lower contact outer edges of the same tire? In this case, the outer edges should wear more than the center when the tire is
over-inflated, not under-inflated as is commonly believed. This is exactly what the OP states of such wear in his original post.. "...have been over inflated if anything...".
Even I am not sure about the above "wear" implication, but I like to keep an open mind. One might be able to detect the best inflation by just tediously choosing the tread inflation shape that yields the lowest TPMS temperature reading. Any scrubbing definitely adds heat, but less scrubbing adds less.
I did a fair amount of tire work on passenger, truck and tractors at my job when I was in high school and learned a lot, not necessarily all from older employees. This was back when belted tires first began to appear. From that and experience since, I can say that very few tire shops fully understand what they are doing and "old wives tales" do very much abound, so a healthy grain of salt is advised. This caution also goes for alignment, balance and ball-joint replacement. Shop training is often more sales-tactic than tech-tactic and probably always was.
The odd wear on the outer passenger and inner drivers front steer is probably caused by the necessary chronic drainage crown on both country gravel roads and paved highways. Even on interstates, the RH lane has this same RH downhill crown. All vehicles are then forced to steer slightly uphill while driving straight ahead. This crown is even known to cause the front passenger ball-joints to wear quicker since more weight is also tilted to the front rh steer tire while it jitters along down the road.
The more even additional wear on outer edges of the steer tire is due to side wind and this should actually be detectable by added front tire temps during intermittent windy area's on such days. But the overall wear should still be slightly more on the outer edges because, although both sidewalls roll slightly, greater weight-shift is on the downstream tire in a wind or downhill crown. As an example race cars generally have the camber changed (to lean in) to accommodate turn-traction, a flatter tread contact pattern during turning on the more heavily loaded tire. In such a case, the tire tread is flatter, rather than tucked-under when the sidewall rolls. If tires could just roll ahead on level ground with no side forces, with no tread squirm, they shouldn't wear at all. Of course there is always some tread squirm, even level.
Wes
