I knew that !
However I thought that it was like the change in the UK from 13.50-20 to 14.00-20 and 10.50-20 to 11.00-20 where for a while the tyres were marked with both sizes. Possibly the term re-designation would have been better ?
In any case tyre sizes are not that precise, particularly the width measurements and do vary a surprising amount between manufacturers.
David
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