I use an IR gun on my tires every time I stop. My exhaust is like you said, about a foot in front of the tires.
Occasionally those tires will be a couple degrees warmer than my other tires but not by very much. A lot depends on which way the wind is blowing.
My generator exhaust also exits there too, right next to my engine exhaust.
My exhaust pipe looks like a Zebra where the black from the high part of the tread has striped it.
2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG
2000 LEXUS RX300 FWD 22MPG 4020 LBS