Here is some general information regarding what “MAX” inflation means on a tire sidewall, as well as more information on how to obtain 4-corner weights on a travel trailer. Hopefully, this will help clear up some RVtravel.com readers’ confusion on these topics.
Regarding “MAX” on a tire sidewall
I do not know why people choose to focus on a single word out of the phrase “Max inflation xx psi at yy pounds load”. Maybe someone can explain to me why this is so confusing to them.
Here are some facts
Fact: Tires have a Maximum load capacity as identified by the tire company.
Fact: Load capacity is a function of and is directly related to the inflation pressure.
Fact: Increasing tire inflation will increase load capacity UP TO A POINT and no more.
Fact: Inflating a tire above the stated highest level WILL NOT result in an increase in load capacity above the stated highest level.
Fact: Unless specifically stated otherwise, discussions on tire inflation are ALWAYS talking about inflation when the tire is at AMBIENT Temperature.
Regarding 4-corner weights on travel trailers
I received the following question/statement on travel trailer tire inflation:
… The (incorrect) assumption would be the total weight divided by 4 is what is on each tire/wheel assembly. More often than not the tires are unequally loaded because of the way trailers are built and having the wheel position in the center of the vehicle. Meaning doing a calculation of total weight divided by 4 and inflating tires from that number …. one tire will be underinflated. Or at least have no inflation margin.
So doing the basic, simple and wrong thing of simply dividing the total scale reading of the 4 tires by 4 and then looking at the inflation tables is certainly one way of having an underinflated tire.
My reply:
Learning the individual tire weights requires some effort. However, if you do it at least once with the RV loaded to the heaviest you expect, and then do the math to determine the “Load Split,” that would be a good step toward preventing tire failure.
Example:
Assume you get the “4-corner” weights (weight on each individual tire) and learn you have 2,350# and 2,110# right and left of front axle, and 2,480# and 2,290# right and left of rear axle. This is how I would do the math: Total front: 4,460#; Total rear: 4,770#—means you have a 48%/52% split.
The heavy axle with 52% of the total also has a side-to-side split 52% on the heavy end.
So, in the future on a truck scale when you get all 4 tires in one weigh number of 9,700, you need to do the following math: 52% of 9,700 = 5,440#. One end of that would be 2,623#.
Then I would go to the Load Inflation tables for that size tires and find the inflation cell that exceeds 2,623# and see what the minimum inflation required to support that number is. That PSI is your new inflation until you get a new weighing and do new calculations.
You will note I always round UP with the weight calculation, and again go UP when reading inflation charts.
Roger Marble
MORE ON RV TIRES
- Do you need to balance RV trailer tires?
- Do your RV tires say ‘MAX PSI 80 psi’ or something similar? Don’t take it literally
- I don’t calculate my tires’ PSI daily. Why do you?
- My RV tire pressure is showing a significant increase. Is this OK?
- Is the tire pressure too high?
- Should you adjust tire pressure when temps get colder?
- Do not adjust your tire pressure for ambient temperature
- Understanding what temperature change does to tire pressure
- Balancing RV tires 101, and a reminder about ‘cold’ inflation
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