[jodrellblank]

That doesn't pass a sniff test; emitting 5 grams of tyre rubber per kilometer, a 12Kg tyre would be completely vanished in 3000km but really they can last 60,000km with only the tread worn down beyond safe levels and the bulk of the tyre still there.

[hugh-avherald]

Looks like mg was changed to a g, though I'd suggest even then the estimate is too high (but probably to the correct order of magnitude).