The case for the retread
Page 29
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THERE WERE TWO comments made in your "the case for the retread" (CM July 1 9) which I believe require correction at least as far as Dunlop Tyres are concerned.
First, the statement is made to the effect that the thickness of the underpattern rubber is reduced during a tyre life. NOT SO. The specific purpose of the' underpattern rubber is to provide the facility for regrooving and to provide a buffer against penetrations and cuts in the tread.
The Dunlop regrooving manual and product leaflets clearly recommend that, for example, with our 11R22. 5 the
cutter blade should be set at 51/2mm when 2mm of pattern remains giving a cut of 31/2mm
into the underpattern rubber, compounded for this purpose.
Provided that the recutting is done in time, and skilfully, a cost effective life extension can be obtained with adequate protection still being provided to the casing.
The second comment, that follows immediately after, con fuses tie-bars with tread-depth indicators. For instance, while the current range of Dunlop heavy radials includes tread depth indicators to assist the UK operator to recognise when his tyres are approaching the legal limit and to meet the requirements of American legislation, it does not incorporate tie-bars which are an integral part of a tread design. There is in fact no reference to tread wear indicators in the ECE legislative proposals.
P. W. ROSS Marketing Planning Manager Truck Replacement Division Dunlop Ltd