What's holding my tyre to the rim?

Q. Why does the rear wheel of a motorcycle not spin within the tyre? A great emphasis is placed on maximising tyre grip against the road surface, so why do the wheels not spin inside the tyre – the point, you would expect, to be of the lowest resistance, especially when you consider that lubrication is normally applied when fitting the tyre.

Wouldn’t centrifugal force lighten the grip between the tyre and the rim?
Stephen Good, Euxton

A. If you used a lot of lubricant fitting a tyre and then went out and gave it loads before the tyre soap had a chance to dry out, say at a race meeting or track day, then it could spin.

Early Dymag race wheels had lower wheel sidewalls, so they didn’t grip as well as they could and that cost Ian Simpson a TT win many years ago. But generally the beads, which are a band or belt made of steel running circumferally are designed specifically to grip and seat on the wheel rim.

Original equipment tyres often have different shaped beads, either strands or solid, maybe round-shaped, or hexagonal that adjust the force to make it seat on the rim. That’s why it’s important to go for recommended tyres; the same size doesn’t always mean the same construction.