Spring rate help?

BGTV8

You want not more than 10-15 degrees C total spread between inner, middle and outer tyre measurements and the spread needs to be even. If the temps inner to middle are close, you can drop some camber.

The other thing to remember is that unless your pit is closest to pit entry, you will drop temps in the time take to transit the pitlane .. can be as much as 10 degC or more.

An R-Spec tyre that measures under 65-70 DegC is probably not working hard enough to generate maximum grip.

An infra-red temp gauge is an approximation only - you want a pyrometer with a probe to get into the tread proper for accurate readings, UNLESS the IR technology you are using is top-shelf (professional motorsport quality)