Tire Shoulder Wear Justification

Until 13 April 2022, found significant numbers of main wheels removal due to shoulder wear, 20 of 21 wheels removed were caused by shoulder wear until ply visible, please refer to Appendix 1. Refer to the Daily Check Sheets, all related wheels were inflated within normal range (200-210 psi), but shoulder wear still occurred. For the CSI record of M01 – M17, the majority of these tires have reached 200+ cycles. Bridgestone assumes this shoulder wear is caused by more road surface contact in shoulder area which is caused by inflation pressure control. The study of Bridgestone and MAA results in a recommendation to keep in-service pressure in the optimum level (210 psi. ) This In service Evaluation (ISE) practice for IAA is required to monitor the tire performance on a daily basis, Bridgestone proposes to aircraft A320 installed by BS main tire PN: APS06755. The daily check item include: Actual inflation pressure monitoring and record it in the check sheet. Once the inflation pressure is less than 210 psi, then have to adjust to 210 psi again. Note: Please record the tire inflation if performed. Actual RTD (remain tread depth monitoring). Measure the remaining tread depth daily, and record it in the check sheet. Actual CSI (Cycle Since Installation), taken from the AMOS and recorded in the check sheet. Shoulder wear phenomenon are disclosed on page 56 of Bridgestone Blue Book (See Appendix 4).