Repairing Defective Treads
by courtesy of the Retread Manufacturers Association
This article is an excerpt from the RMA’s technical training manual, “Retread Process – Workshop Practice”.
Although every effort is made to produce quality retreads, defects or blemishes will arise which may be suitably repaired and then passed to finished stores as first quality stock.
Minor repairs may be effected anywhere on the retread, although the defective area occurs mostly on the sidewalls. These minor defects are often no more than surface blemishes in the form of lightness or blisters which can be repaired without being readily apparent or unduly detracting from the appearance. If the blemish is consistent, check that it is not caused through lack of venting in the mould or contaminated mould/sideplate surfaces.
Service and safety are the prime consideration and any repaired retread must fully meet these requirements. If in doubt, the retread should be rejected or a more experienced person consulted.
Much depends on the particular company and their standards as to exactly the company policy, which is adopted. It follows that the higher the standard, the greater degree of quality control required to maintain the standard. However, it must be emphasised that it is more satisfactory and far less troublesome to handle a consistently good quality product. Skilled operators are required for any repairing operation, but even they cannot produce a top quality retread from a mediocre product.
According to the nature of the repair, it may be effected with or without applied pressure. Most blemishes are removed simply by buffing with a carborundum stone and then polishing with a revolving rag wheel or similar. Special purpose proprietary machinery, materials, tools and instructions are readily available.
Whilst most after-cure repairs are dealt with in the inspection department, some which require more detailed attention are returned to the main repair section.
Retreads which, after repair, have an inferior and unacceptable appearance but fulfil all other service requirements are sometimes disposed of as a special clearance lot. However, the legal marking requirements must not be removed. Further, the retread manufacturer remains responsible for the product during the service life.
After any repair is complete, the tyre is returned to final inspection for approval.