after 1 run at road atlanta ,tire pressure was 39 front/49 back ,when I let off air prior to next run ,the warning light pops up if I let out 7 lbs or more ,stays on ,this has happened twice . any ideas. thanks bob

 

What pressure did you start the run on?

When tracking your car, you are at the lightest load, so, there are different settings for the tires than the door sticker carries.

I think light load is 33 fronts/39 rears. Once the tires are warmed up (after first session) check the pressure.

I did the same thing on my first DE. Let too much air out and the warning light came on. Also noticed the front tires starting to roll.

It sometimes takes several miles before the sensors can recalibrate after setting off alarms.

My track tires have no monitors in them and when I change back to the stock wheels with sensors, it takes about 30-40 of continuous driving before they re-calibrate.

Don't forget to change the load setting in the on-board computer.

 

Same thing happened with me but I found that the TPMS is too slow to actually use as an accurate gauge of air pressure.
The old fashioned hand held tire pressure gauge is the way to go for the track.

So don't worry about what the TPMS says when you're adjusting tire pressures on the track, just refill to recommended pressures after the event and reset the TPMS using the on-board comp (as Looney2N already mentioned).
Takes a bit of time but it eventually recalibrates

 

I have put on and removed the track tires 2 different times now. The track wheels have no sending units and I am running Nittos at 33 lbs all around.

The first time I put the factory wheels back on (with sending units), it took 20+ miles before the TPMS went back to normal.

Today it took less than 5 miles, but the my hand gauge reads 33f/39r and the TPMS reads 36r/43r..........the TPMS is just not that accurate.

Must be because it is such a clear and sunny day

 

Start at 27F and 30R and don't worry about the light, your pressure will go up after a few laps.