Could it boil down to just needing more frequent tire rotations?
Or something like worn suspension components?
Alignments have been performed regularly so that seems unlikely to be the cause.
Which worn suspension parts typically lead to this issue?
Car is nearly 20 years old, 135k miles. Scion (Toyota).
The most likely cause is you've got worn suspension parts which are causing camber issues. About alignments ... most vehicles do not allow for alignments to be done in the rear ... there's no adjustment there. So even though your alignment is kept fresh, it doesn't mean there's actually anything happening there. The can check alignment, but they can't do anything with it. If you have worn bushings which are allowing the camber to self adjust during cornering, the alignment could still be showing good during the alignment check, yet be causing the wear on the tires.
