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Exercise causes shoulder cracking.
I am a tire salesman, and what I saw above should be the scratches caused by the contact between the side of the tire and hard objects. It has nothing to do with tire quality. You can look at the production date of the tire. If the tire exceeds its service life, any damage is normal. Drivers are advised to replace tires after they have been used for a certain number of kilometers or three years. Safety tires lead the future!