need 3/10th

10x26 Hoosiers on how wide a rim? You mentioned there's a inch of tread on each side that doesn't touch the track? The tires are over-inflated then and less pressure makes the car squirrely at speed. You need narrower tires for the rim size or wider rims for the tires you have.
I run 8x15 inch in the back, Hoosier recommends from 8-10 inch.
Just a half inch on each side with 16 psi.