I did find this info on line:
maybe I can use it as a guide:
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I also use a IR gun and really like it better than burning my hand.
I have found that on a really hot day, as stated above, the temp. will get to 135 deg. (The highest I have recorded.) Normal around 90/95. You want both sides to be close in temp. and there will be some variation between front and back hubs. but not more than say, 5-10 deg.
One thing I noticed, when fooling around with the gun, is that the hubs, wheels and even the tires were very close to the same temp.