They do. And cross-plies squirm much more than radials which is why the
latter give much better grip and wear, but they still squirm to some degree.
The biggest discrepancy is that my tyre measured 1940mm circumference
whether inflated to 24psi, 10psi, laden or unladen. But it only travelled
1885mm at 24psi and 1876mm at 10psi. However the rolling radius (which is
what is used in speedo calculations) indicated that it should have travelled
1823mm at 24psi and 1615mm at 10psi.
PaulH.
----- Original Message -----
> For one rotation of the
> tyre, unless the tyre is slipping on the road, the tyre will move forwards
> by the distance arounds its tread.
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