Using a reference level tire gauge http://www.longacreracing.com/catalo...id=982&catid=8 , my TPMS system consistently reads about 1 lower. One could argue I then should set the differential reading to be minus 1; and that's what I do, roughly, between 0 and minus 1.

If yours are minus 4 both F & R, then either your tire gauge is off, or the 4 TPMS sensors are off. Since it's statistically unlikely for the each of the monitor to be off by such similar large amounts (assuming that the rest of the system is fine -- very likely?), I would guess/speculate your tire gauge is off. Just guessing and if I don't make any sense at all, I understand.

Tiago,
See Doug's response (TT Gasman) above regarding tire pressure at the track. Or PM him.

 

I first thought it must have been my gauge, so I pulled another gauge - both pretty good quality Moroso gauges but definitely NOT reference quality, but both read within half PSI of each other and both read 3 PSI (not 4) higher than the TPMS reading. I'll have to borrow another tire gauge and double check but would like to hear from more people who have compared their TPMS reading to their gauges.

 

Your results are the same as mine (TPMS consistently reads 3 psi too low at all four tires) and I have used three or four high quality tire pressure gauges.

 

I will start with 30-36 cold, and then after each session, i will monitoring the pressures till it reach the maximum of 36-44 on track, as Doug advice. After the trackday, I will post here the cold pressure to reach that goal on track.