The “MAX PSI” number on the tire sidewall IS NOT the maximum psi a tire can tolerate. Yes, this wording can be confusing. But remember, it was written and approved by federal lawyers.
What it really means is that an increase in PSI above that number WILL NOT result in an increase in tire load capacity above the pounds listed on the tire sidewall.
Load and inflation are directly connected
People know, or should know, that load and inflation are directly connected, and you can see that in every Load & Inflation table.
An obvious separate question then is: Why does Roger recommend tires to be inflated to 10% more PSI than indicated in the Load & Inflated tables?
This comes from my discovery of the excess “Interply Shear” in the belts of radial tires when used in a trailer application. More on that force in these two posts from my blog:
- Warning: Super technical post on tire failure and interply shear
- Another question on why trailer tires fail more often than tires on motorized vehicles
Please DO NOT bleed air out of your tires on a hot day when your TPMS reports a number higher than the PSI number on the tire sidewall. Your undamaged tire will not “blow up” from too much pressure.
Your PSI will change by about 2% for each change of temperature of 10°F. But if you have properly set your “cold psi” based on the scale reading of the weight on your RV, you should not see your pressure increase by much more than 20% to 25%. If you see that much increase, you are probably driving too fast, or there is some other problem such as dragging brakes or bad wheel bearings that are heating up your hub and wheel.
Roger Marble
Check out my Blog www.RVTireSafety.Net
Read more from Roger Marble on RVtravel.com.
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A completely understandable article with no technical mumbo-jumbo that usually goes over my head. Thank you, Roger. I’m a 60 mph max TT towing kind of guy. So far, no blowouts in over 25 years. I’ve probably jinxed myself now – 😀
I rarely top 65MPH and have not had any blowouts either. Speed kills TT tires
I never paid much attention to the MAX psi until I got a pair of Goodyear Endurance tires. I discovered an actual psi vs load chart on Goodyear’s website for that particular tire. I add about 10%-15% to the recommended psi for the weight of my trailer and have enjoyed smooth towing and no (knock on wood) blowouts. Some folks have mistakenly stated that tires should always be filled to the MAX psi. Totally wrong!
Thank you, Roger! I did not know this. Thank you for tirelessly educating me still again! Merry Christmas! 🙂🎄🎁
I repeat what Neal said below. Thank you Roger !
I have always assumed the molded PSI rating on a tire sidewall tire was not the same as the molded in weight rating of that same tire (single or dual). Each tire has its own specific weight limit and cold pressure, not to be exceeded by any stretch of the imagination. And if it is ever necessary to over inflate a tire, the tire capacity is too low for the load it carries.