Don't stock car racers measure the circuference of the tires instead of using airpressure? Like thew person before said atv tires will sometimes be different sizes with the same pressure. It can happen when making the tire and putting to much air in the tire to set the bead on the rim.

 

even with that low of a psi? I would imagine it wouldnt be that noticeable

 

just save your self the time and money and use a tire gauge!!!!! They work nice. Keep trying!!!!