BRIDGESTONE | RETREADING
WHAT ARE THE MAIN DAMAGES REJECTED BY RETREADERS?
There are several types of damage by which the casing could be rejected by a retreader. Here we explain the 14 most common damages found on tyres, what causes the damage and how it can be prevented.
1. CIRCUMFERENTIAL INNER LINER CRACKS Destruction of casing from service at low or no inflation pressure, generally following the sequence of discoloration, distortion, blistering, wrinkling, abrasion cord break-up or destruction of the casing on one or both side walls. Cause: Continuing to run after air loss, acute under inflation pressure; rim, valve or valve extension leakage; deflation due to overload.
2. LINER DEFECTS Cracks in the interior of the casing. Radial body ply cables showing through the liner. Cause: Liner defects are usually related to excessive heat build-up that might occur because of impact, curbing, under-infaltion, overloading, exposure to extremely low temperatures, casing fatigue or a casing manufacturing irregularity.
3. INNER LINER BUMPS, BULGES OR BLISTERS Bumps or bulges in the interior of the casing. Cause: The most common causes for this condition are mounting/dismounting related bead damage, repair failure, curbing or lateral scrub. The damage can also be caused by casing fatigue or original casing manufacturing irregularities.
8. SCRATCHING ON THE SIDE WALL Damage caused by contact with a part of the vehicle. Cause: Improper size selection, damaged vehicle, worn or broken suspension components.
9. SHOULDER BULGE, RUPTURE OR SPLIT A bulge in the shoulder, semi-circular rupture in the upper side wall or split in the shoulder. A separation in the belt package will usually be associated with this condition. Cause: Causes are lateral scrub, liner damage, repair failure or casing manufacturing irregularity.
10. SIDE WALL CUTS OR SPLITS Any damage to the side wall such as abrasions, cuts, tears and penetrations. Cause: The damage can be caused by chains, contact with vehicle components, curbing or vandalism.
11. BELT EDGE SEPARATION Loss of adhesion occurring at the belt edge between belts extending less than halfway across tread face. Cause: Improper pressure, excessive load, improper repair, accumulative tyre abuse, excessive speed, run flat, excessive heat, prior damage, improper storage or misapplication.
12 JUNE 2011 real QUESTIONS real ANSWERS
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