Regrooving row
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• The long-running disagreement between Michelin and the Retread Manufacturers' Association over the advisability of regrooving truck tyres has intensified with news that the tyre company is revising its regrooving recommendations.
With effect from January 1 this year, the recommended regroove depth of several types of Michelin truck tyre has been increased by a millimetre. For an 11R 22.5 with an XZA tread pattern, for example, the recommended regroove depth has gone from four to 5mm.
As before, the recommendation for Michelin's own remould tyres, branded Remix, is that the regroove depth should be a millimetre less than with a first-tread tyre.
Michelin says that on the tread patterns for which the regrooving recommendation has changed, (XZZ and XZY are among those which are unchanged) it has successfully tested the deeper regrooving in other European countries before introducing it here. Brian Lawton, technical executive of the Retread Manufacturers' Association which represents the UK's independent retreaders, responded to news of Michelin's new regrooving recommendations by saying: "I am aghast. This is bound to worsen the already bad effects of regrooving." Since 1985 the RMA has campaigned vigorously against regrooving, saying that it leads to damaged casings which cannot be retreaded and to illegal tyres with plies exposed.