It took me a while but I found it: https://news.ycombinator.com/item?id=30501072
Check all the subthreads and links, they're not that many.
The formula was actually for road damage, but my bet is on road damage being strongly correlated with tire wear.
> And the worst part for the wire tear (and I think road tear), apparently it scales to the POWER OF 4 (!!!).
That's very interesting. I'm a default sceptic, but would love to learn more, because if true, that could nullify a lot of the local air arguments. Do you have any sources for these?