All four of my Sumitomo HTR+ 235/45/17 tires have noticable cupping on the inside.

What is the most likely cause of all four of them cupping on the inside? I have about 27k miles on them, and have rotated them on a regular basis.

Front end alignment checks out ok, by the way.

I will appreciate any advice or suggestions.

 

Cupping is usually caused by underinflation but I thought it should be both inner and outer sides.

 

are those Sumis sitting on stock rims? I've heard of problems with some tire manufacturers getting 235/45s to sit correctly on our thin stock rims

 

Yep, they are on the stock rims. I wouldn't have thought of that as being the culprit. Thanks.

 

mine also, i had the vehicle aligned when i got them put on at my dealership, its been about 1500 miles since i mounted them, and the fronts are cupping on the inner and outer edges, i had him recheck it, and the alignment is fine, i raised my tire psi's to 36psi and have driven it since last week, i have to wait until i put more miles on it to see if it gets worse, the ride is slightly stiffer, but i really don't mind, still takes the major bumps ok