Car has 45K miles and we are about to buy the third set of tires. We get about 18-19K per set of tires before severe cupping becomes noticible through vibration in steering wheel. Dealer says nothing wrong with car. Is this normal war (new set of radials every 19,000 miles? Note: car is manual transmission & we bought it new. Local mechanic says wear due to no weight in back of car which cause it to bounce and wear out quickly?
Has the alignment ever been checked and do you rotate your tires?
Cars do not normally cup their tires. The dealer is trying to duck out of warranty work. The local mechanic seems unaware that virtually all cars go around with no weight in back but show no tire problems. You DO have a repairable problem, either with alignment or front suspension. Press the dealer and save all your paperwork. You may have to kick this one upstairs.
Tire cupping is caused from worn shocks/struts.
I’d suggest a reputable independent shop that specializes in chassis work. Struts/shocks are a common cause (as Tester said), but there are other possibilities. In addition to things like tie rod ends, even things like a slightly dented wheel can cause it. Normally that would be noticed when installing a new tire, but it’s an added thought. A Road FOrce Balancing could at least conclusively eliminate the rims as a candidate.
I’m not quite sure of the difference between cupping and rear tire irregular outside tread row wear but we have consistently gotten that on several front drive cars, all of which were bought new and when I got lazy about rotating the tires on time per the owner’s manual. Wheel misalignment and worn shocks were not the problem. It just happens with a front drive vehicle for us. Our rear drive cars were not sensitive this way. Narrow tires will repair themselves after a few or more thousand miles after rotating but wide tires will not; will stay noisy.