In reference to staggered tire sizes? (I.E. smaller tires on left side)

Or are you talking tire sizes in general referring to gearing and the effects of different tire sizes?

I'm assuming you're talking about staggered tire sizing since you're asking this question in a circle track thread and the latter question is more general mechanical knowledge.

On dirt we run anywhere from 1/2" to 1 1/2" across the front and 2" to 7" across the rear (full bodied cars only as sprints run way more).

In circle track racing staggered tire sizes do a few different things.

A larger right rear tire (running a larger difference across the rear) allows the car to "roll" into the corner under throttle, it will also make the car feel "loose" upon exiting the corner on the throttle.

When running mismatched tire sizes you inherently loose straight away speed as the right rear will always be covering more ground than the left rear and the force of the rear is always trying to force the car to turn left.

The "correct" stagger is the amount of stagger that allows the rear tires to turn at the same revolution while going through a turn.

With modern chassis technology much of the effects of tire stagger can be tuned out of the car rather easily as long as you are not running an extreme amount.

All of this is also true for asphalt except they just run smaller amounts of stagger.

Running a spool vs running a locking rear will produce different stagger effects.

I'm not really sure exactly what you want to know or what you're trying to do so that's just very general information. I can help you some more if you can give me a specific question.