I went to have the tires rotated today and the guy called saying they wouldn't because the inside of all 4 tires were worn excessively (bald, as he said which I don't believe)

Anyone have any thoughts on what might be causing this? Totally stock 430 with factory 18" wheels. No issues at all currently. Seems to drive and ride very well.

 

Have you got the alignment checked? Most likely too much negative camber. Front is adjustable. Rear you have to buy aftermarket adjustable control arms or Lexus sells 1 longer and 1 shorter control arms to adjust camber by .7 degree + or -.

 

Your lower arm bushings are probably toast and even if it reads as in alignment static going down the road they will not stay there.

 

I'll take a look at the bushings when I get home later...last time I checked they looked fine.

also, 103k miles on the car currently.

 

The rear bushing...?

 

Both, if they are able to collapse under driving load (the toe in angle WILL compress them just rolling along) it will do exactly what he is seeing. My car was like that when I first bought it, on the alignment rack all was well but it killed the tires that came on the car

 

I have the same thing starting only on the drivers side front on the OUTSIDE edge...

 

Well that I would check alignment before doing anything, usually it's the inside that dies from bushing failure that allows the arms to move too far out/up. Unless the uppers have come out of adjustment I don't think that would happen from wear.

You seem to care about your car a good bit from what I've noticed here so if you do find something wrong I would replace upper and lower arm bushings as the front strut mounts so that everything is at the same level of wear and uneven loading doesn't occur and further accelerate the rate older parts degrade.