> I think as a starting point, I would expect that tire wear should remain roughly in proportion to road wear
IMO this would be a suspect assumption to make w/o data to back it up. You've got two dissimilar materials interacting (in very different modes). E.g. rolling a metal ball bearing on a wood surface would obviously cause the wood to degrade far more than the ball bearing, (and even a wooden ball rolling on a wood surface would wear substantially less due to the mode difference).
(If I had to guess the road has a higher wear as the surface has a tensile stress around the contact patch of the tyre, causing most of the damage, but this is just armchair engineering at this stage).
The point I was after to make is that you can't assume that road wear scales the same way as tyre wear (I was assuming same material fwiw, just different loads). They are being worn under very different modes/scenarios.
Given that roads and tires experience the same forces under driving conditions (Newton’s Third Law guarantees this) I think it’s a reasonable prior assumption to start from. There are of course other environmental factors that accelerate road wear (rain and water erosion, freeze thaw expansion) but those conditions were not included in the study that produced the Fourth Power Law.
IMO this would be a suspect assumption to make w/o data to back it up. You've got two dissimilar materials interacting (in very different modes). E.g. rolling a metal ball bearing on a wood surface would obviously cause the wood to degrade far more than the ball bearing, (and even a wooden ball rolling on a wood surface would wear substantially less due to the mode difference).
(If I had to guess the road has a higher wear as the surface has a tensile stress around the contact patch of the tyre, causing most of the damage, but this is just armchair engineering at this stage).