The minute you get off track level the tires off. You will never have the same pressures at first on all 4 corners. Certain tires get worked more then others. So using your example level them all down to 12.5 hot. When they cool they may have 4 different pressures, that’s ok. Now next session they will all heat up to 12.5 (barring any crazy weather changes) . Now you can adjust the pressures to suit the drivers/karts needs. Do that cold by either adding or bleeding down all 4 tires by the desired amount. Hope that made sense. That should get you rolling…

Just set the pressures cold. Keep track of your pressure gains on all four corners, but don’t set pressures hot because you don’t know how much they will change when the tires cool back down between sessions. Check pressure on the grid before you go out and set them where you want them to be.

MG Yellows are usually around 9-11 psi cold.

+1 Matt

What matters is that the tires are the same when at full running temperature.

my step by step process to airpressure is such

1. tire testing!!!!

2. find out how much each tire grows when you do a 10lap and 20lap test session or if your local track does a different format do however many laps they do for heats and main event ( note best way to do this is set all tire to the same tire pressure) also have someone else take tire pressures IMMEDIATELY after you get off the track as soon as you stop using the tires in a “race” setting they start to cool off and you get an inaccurate reading.

3. after you have established how much each tire grows try to get all four tires to grow to the same pressure( remember to continue to do your local racing format)

4. once you get your tires to all come in at the same pressure start playing with tire pressure. You want your fastest laps to be 1-2 laps before the end of the race.  (remember when in doubt always go lower, you want to go lower because if the tires are over pressured the kart tends to go flat and start pushing and life happens)

5. more tire testing those who know their tires the best win races

6. win races