My Vanagon Westy 84 has a weird "cupping" wear pattern on the inside
of the left front tyre. About a third of the width has worn down much
more than the rest and in a ripple pattern repeating every 3 or 4
inches. The effect is a rumbling noise when driving.

Does anyone know what causes this?

Is it either wrong tyre pressure or some kind of wobble in the
steering rack? wobble is likely as I have 300,000 miles on the clock
:-)

Thanks for any pointers

Peter
Westy 84