The caster shouldn't cause tire wear!! However if you remember I suggested that once tires have a abnormal wear pattern they will continue to wear unevenly. One of the problems with radial tires is uneven wear. Most tire companies recommend rotation every 6-7.5k miles. Even Michelins will wear unevenly if they aren't properly cared for. AT the dealer I worked for the alignment "machine" had to be recalibrated every 9-12 months(& it is one of the best!!) Could that be the problem?? Is there any good alignment shops in the area that can check your alignment & print out the finished spec. sheet?

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH