tighted - temperature changes will affect tire pressure especially if you use air. I got the light on the first cold night and the first really warm day. I keep mine at 34lbs. About a year ago when I got my wheels put on they switched me over to nitrogen, "its more stable than air and it shouldn't trigger your sensors as much with temp changes". I wish! I still get the light when it gets cold. So I have gone back to plain old air.