Comment by GuB-42

About tire wear, I know a guy who did custom "Solex" type bike racing, with a small, friction drive petrol engine on the front wheel.

It was so bad that the rear wheel ended up getting bigger at the end of the race, as it picked up rubber deposited by the front wheel!

Keep it mind it was custom bikes though, the front tire just had to finish the race, they used a roller made of hard materials and knurled. I don't remember the reason, but it probably had to do with the fact their engines were quite a bit more powerful than traditional ones despite having the same displacement.