tire pull / radial pull

Hello all,

 

I have a new set of Firestone Firehawk Indy 500 Wide Ovals. I put them on the car and had it aligned. Car was running fine. After a few weeks I did a track day, and afterward I noticed the car pulling to the left. I brought it back to the shop to have it aligned, but the alignment was fine. They said it was radial pull/tire pull. So I swapped the front right and left, and now the car pulled to the right. They're directional tires, so I swapped them back and then just swapped the left side front and rear. Car still pulls to the left.

 

I tried several other combinations, and basically if one of the left side tires is on the front of the car, it will pull to whatever side that tire is on. But if both right side tires are swapped to the front of the car, it tracks straight.

 

The track I ran is a short clockwise circuit, putting most of the load on the left side of the car. Is it possible that these tires just suck and the wear on that side after one track day caused both left side tires to radial pull, or perhaps they both had a belt misalign? They've still got 90% tread!

Tape measure, at midpoint of tire, measure circumference. Repeat on all 4 and compare.

Just to confirm - measure each tire at the center of the tread? What will I be looking for?

 

Should I measure the circumference of the inside and outside tread of each tire?

You measure around the tire, the circumference at the center line of the tire. Compare the four of them. If the difference is significant, that could explain the pull.