TPMS Question

rlw999 wrote:

CA Traveler wrote:
Check your tire specs for the maximum pressure. TST indicates it should be about a 25% increase.

The maximum pressure on the sidewall is the maximum *cold* pressure, so it doesn't really help determine the max pressure for warm tires.

OK The TST 507 manual states the pressure data charts plus about 25%. Hence the psi is based on the actual weight the tire is carrying after it is weighed plus 25% for the TPMS.

Thanks for the replies. I think I will set the high at 96 and take it from there. For the low I will set at 70

CA Traveler wrote:
Check your tire specs for the maximum pressure. TST indicates it should be about a 25% increase.

The maximum pressure on the sidewall is the maximum *cold* pressure, so it doesn't really help determine the max pressure for warm tires.

As the others have said, TST recommends 10% below and 20% above. One hot summer, I got the over pressure alarm 104psi , high for the 80psi tire pressure was set for 96 but all tires were equally high, I reset the high for 105 psi.
Another note, one trip I used my infrared temp gun and found tire temps just over 150F. I checked the 18 wheeler beside me in the rest area and his temps were 175F/

Ken

I use 10% below to 20% above. For an 80psi tire, I would use 72psi as lower limit and 96psi for upper limit.

For reference, a 20% increase in pressure would be a ~60C (~100F) increase in temperature over ambient - that is getting really hot. If you saw that on your TPMS, you would want to pull over and check things out.

What "ford truck guy" said x2

Check your tire specs for the maximum pressure. TST indicates it should be about a 25% increase. I've seen 10% which does not include hot summer days on the MH.

I have both an internal sensors system (Smart Tire) and TST. The psi difference is 1 psi. The internal sensor temperatures range from 41 to 54 derees higher than the TST values. I attribute this to the TST sensors being mounted outside the tire on brass valve stems and rotating itn ambient air. In other words external sensors have significant lower temperatures than the actual tire temperature.

Stopping and quickly measuring the tire sidewall tempeatures resulted in values 6 to 26 degrees below the internal temperature.

Nine pound increase in an 80 psi tire is normal.

I just installed the TST 507 series and they set it up for me... I run my tires at 115 psi... the low is set to 103 psi ( 10%) and the high is set to 144 ( 25% ) ..

They told me the standard was 10% for the low and 20-25% for the high setting

I just ran from PA to Richmond VA which was around 300 miles... 1st half was rain and mid 60's.. the psi was 120-122 psi... the 2nd half was sunny and mid 70's... the psi was 138-140... I am curious to see what they show when running in 100 degree heat down south......