25% increase in tire pressure during the day (above max)

chracatoa wrote:
Jadatis and others, thanks for your reply.

I rarely tow faster than 65 and my cruise speed is 60mph. I only do 70mph (max speed for me) when I'm overtaking someone that was going <55mph and decided to speed up for some reason.

The tires are new (Carlsisle) and they can take 10lbs more than the original Towmax (negligible).

Firs thought you meanth 10 psi but you probably mean lbs and then the difference in Maximum load of 10 lbs is neglible, most likely a rounding difference in combination with conversion difference only and old and new tires can bare the same.

chracatoa wrote:

GMandJM wrote:
To borrow a line from Ronald Reagan (who co-opted it from a Russian proverb): Trust but verify.

I had already noticed a difference of ~1.5 psi from me measuring it and the sensor. The numbers here are adjusted for that. (e.g. I read 50psi but sensor was showing 48 or 49).

Yep, that happens. As long as you use the same gauge and the difference is consistent it's not a problem.

as a point of reference on my truck, running LRE tires, 65psi cold, I commonly see a 10-15F rise in pressure on a hot day.

On my trailer, running LRE tires set at 75psi, 90-95psi on a hot day and an internal temperature of 130F is very common.

In neither case am I running very close to the max load rating, well below it.

so, while the OP temp rise %wise is higher than what I see, it doesn't seem out of reason, especially if he/she is running near max load rating on the tires.

I would be curious to know what would happen if you started at 55 psi. It would be perfectly acceptable to fill to 55 psi cold and you will see less percentage increase due to less internal heat.

GMandJM wrote:
To borrow a line from Ronald Reagan (who co-opted it from a Russian proverb): Trust but verify.

I had already noticed a difference of ~1.5 psi from me measuring it and the sensor. The numbers here are adjusted for that. (e.g. I read 50psi but sensor was showing 48 or 49).

93Cobra2771 wrote:

4X4Dodger wrote:
Many TPMS are unreliable, inaccurate and suffer from misreadings in all kinds of situations. I would not rely on them. To me they are just an "indicator", something to be viewed in terms of broad percentages.

But I agree with most here that the rise in psi you see is perfectly normal.

Out of curiosity, what is the basis for this statement? How many brands have you tested?

TPMS errors and issues can usually be attributed to user error and/or improper maintenance.

Many (if not most) of us who use TPMS systems have checked their reliability by comparing the TPMS readings with IFR guns (temp) and hand-held air gauges (pressure).

To borrow a line from Ronald Reagan (who co-opted it from a Russian proverb): Trust but verify.

Jadatis and others, thanks for your reply.

I rarely tow faster than 65 and my cruise speed is 60mph. I only do 70mph (max speed for me) when I'm overtaking someone that was going <55mph and decided to speed up for some reason.

The tires are new (Carlsisle) and they can take 10lbs more than the original Towmax (negligible).

4X4Dodger wrote:
Many TPMS are unreliable, inaccurate and suffer from misreadings in all kinds of situations. I would not rely on them. To me they are just an "indicator", something to be viewed in terms of broad percentages.

But I agree with most here that the rise in psi you see is perfectly normal.

Out of curiosity, what is the basis for this statement? How many brands have you tested?

Jadatis: That is very interesting (j-half says to tell you "BRILJANT!"). You've obviously put much effort into understanding this subject. Thank you for sharing your knowledge.

Many TPMS are unreliable, inaccurate and suffer from misreadings in all kinds of situations. I would not rely on them. To me they are just an "indicator", something to be viewed in terms of broad percentages.

But I agree with most here that the rise in psi you see is perfectly normal.