When checking tire roll out. How much air are you guys running.trying to check my current slicks before I dismount them.this is a 29.5 10.5 m/t slick

I always checked them at the pressure I run and
used a cloth tape(seamstress tape) to measure
them.. I did it both ways.. lay the tape on the
ground and rolled over it then raped it around the
tire.. then jacked it up and raped it around the tire
just to see the difference.. with the tire off the
ground it was always larger but I dont recall how much..
and I did both tires.. sort of a PITA but its needed

My 2-cents.
For that tire check it at 10 psi and 15 psi (whatever you run). The 10 psi may be more representative of the manf spec, but I prefer to use the actual pressure I run.

The tire pressure is determined by the size and type for each tires, radial use a lot more pressure. A big 14x32x15 bias plys will use less air pressure (5 to 7.0 lbs)than the smaller size 10x30x15x bias plys will(9 to 12 lbs). The rinm width and track conditions also are used to get the best pressure that day for the best 60 ft for the conditions When I mount and check the circumference on a new set of tires I will use the pressures that have work best on my car for that size tire, if it is 10.0 lbs and I have more than 1/4 inch difference in roll out I will over inflate the smaller tire to get it to be the same size or even 1/4 to 1/2 inch bigger and let it sit for 6 to 10 hours and then let the pressure down to match the big tire and check the circumfence agian. repeat as needed to get them within 1/4 of each other. If the differences are more than 3/4 inch to start with I call and ask for another set of match tires and return the bad ones

By the current time slip I think you got a handle on that "rollout" Shiloh! congrats!

Thanks j it is getting faster every outing but will not leave on the trans break on the radials so this is a foot break way off in the 60ft