Rollochrome wrote:
My Carlisle CSL 16's have a cold max pressure of 110.
I installed a TPMS the same day I bought them.
I read up on these tires and there was nothing about a hot max pressure from Carlisle. I contacted Carlisle and they said there was no "hot max" specified.
So on the maiden voyage with them, I watched the temps rise and rise above 110 to just under 120.
The tires on the sunny side were uniformly higher than the ones in the shade side understandably too.
I read elsewhere that a different manufacturer emphatically states on their website regarding trailer tires to NEVER bleed down HOT tires.
So it begs the question, how much hot pressure is too much? The TPMS system instructs to set alert levels that are pretty high.
What do you think is an acceptable pressure level hot relative to the cold max?
First, the burst pressure of tires is many times the max pressure listed on the sidewall. In this case we are talking over 300 psi! Yes, you read that right! (Be aware that a road hazard is NOT bursting the tire! It is damaging it! So that can occur at ANY pressure!)
Second, Rule of Thumb is that the increase in pressure from cold to hot shouldn't be over 10% (excluding ambient temperature effects.) In this case a 110 psi tire shouldn't exceed 121 psi (excluding ambient temperature effects!)
If you exceed 10%, then you need to do something about increasing the load carrying capacity of the tire = more pressure, larger tire, slowing down! If you exceed 15%, you need to do this IMMEDIATELY as that tire is going to fail fairly soon!
Ambient Temperature Effects = 2% increase for every 10°F increase in ambient temperature. So a 110 psi tire set in the morning when it is 50°F, in the afternoon at 90°F will be at 115 psi, just due to the outside temperature.
Michelle.S wrote:
I know I read it on one of the Tire MFR's sites, but don't remember which, but what I remember was trying to set the tire pressure at an ambient temp of 70 degrees. When temps are in the mid 50s the pressure will be approx 10 to 15 Lbs below the set pressure, but within a few miles rolling down the road they will be at the set temp and continue rising as the continue heating up.
No!! That is wrong! You set the pressures to the ambient conditions, whatever they happen to be. The only exception to this is in winter where the ambient temperature is going to be LOWER than when you set it, and you use the "2% for every 10°F" rule while estimating how cold it is going to get.
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An important thing to remember is that UNDERINFLATION is bad, where over inflation only causes minor issues! In other words, pay attention that you have ENOUGH pressure in your tires, but don't be paranoid about having too much.
