Researchers at the University of Bayreuth have, for the first time, provided concrete figures on the abrasion of mountain bike tyres in off-road conditions. Their findings contribute to a better understanding of the global microplastic cycle. They report on their research in the journal „Science of The Total Environment“.
It actually appears to be per bike per 100km. I find that quite surprising given it’s half the number of tyres, there’s substantially less initial volume per tyre than a car’s and, as you say, there’s a lot less weight on them.
Given their focus on MTBs, I wonder if it’s related to the type of terrain being ridden (higher incidence of gravel/sharp rocks than your average road) or different tyre compounds between the two vehicle types.