That's been the benefit to me, still having a drivable rig when a tire shreds.

But, there is also something called a "super single" that's a double wide single wheel/tire, with one on the end of an axle rather than two. I'm told they're cheaper and lighter total, as opposed to the more common two per end. I've pulled a few trailers that had them. I don't really know why one or the other, I just drive them.

I'm sure that's true, but are you saying it doesn't reduce wear?

It probably reduces wear slightly. Increasing contact area necessarily decreases applied pressure. Then again, a wider effective contact profile damages more of the road than a narrower one would.

Let's not forget the context of this discussion, however. Fourth power expressions are still fourth power expressions after multiplication by a constant factor. 4/18 is a constant factor.

You're multiplying the input by a constant factor. If wear is proportional to (weight per tire)^4, and you've halved weight per tire by having twice as many, you've just reduced wear to 6% of its original value.

I don't know if doubling tire counts really does this, but it's hard to see why twice as many axles would help but tires per axle would not. It's possible (the pressure underneath the tires is reduced, but the tires exerting pressure on the road are closer together) but counter intuitive to say the least.

And there's no proof in this thread that it doesn't help except for masklinn's misinterpretation of the original study.

Also, road wear is a function of friction as well as pressure. Friction is increased with additional tires.

This is already taken in to account with the forth power rule, isn't it?

Fourth :)

I'm sure it reduces wear on the tires.

"The AASHTO load-equivalency factors strictly apply only to axles supported at each end by dual tires. Recent increase in steering-axle loadings and more extensive use of single tires on load-bearing axles have precipitated efforts to examine the effect on pavement wear of substituting single for dual tires."

https://www.fhwa.dot.gov/reports/tswstudy/TSWwp3.pdf