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.
I would bet on different rubber being the culprit. My downhill and trail tires are super soft in order to grab the rocks and roots better. They wear out quicker than road tires because of this. Still takes a few years in with me riding every day but it’s noticeably faster than the roadies.