Running tire pressures 2 psi low?

[GregTu]

I’ve been running our ‘24 Platinum with stock tires at the recommended 39 psi cold (adjusting for temperature) for the last year. The ride is a little rough, but it is more truck than car. With the colder weather in Chicago the cold pressures have dropped to 37 cold and we’re noticing a more comfortable ride.

Has anyone tried a lower air pressure? Any negatives?

I wouldn’t tow at the lower pressures, but we take a long driving trip in the winter with a lot of highway driving and wouldn’t mind the extra comfort. Appreciate your thoughts.

 

[JasonH]

You can check the tire load index and adjust pressure for the actual weight you anticipate carrying in the vehicle. But it's better to be slightly over than under, since under can lead to tire failure. But this probably less likely in the winter where heat is not as much of an issue.

 

[Ugh_J]

To expand on what Jason said, tire pressure is a linear function in terms of load capability. If you look at your tire sidewall it will tell you the max load and max pressure. So for example, mine says max load 2679lbs and max pressure 51 PSI. Ergo, it will carry 52.53lbs per PSI. So if my load on that tire is typically 1830lbs (half the axle load), then optimal pressure would be 34.8 PSI. You would need to verify at a scale somewhere, and it will change depending on whether you're towing or have the back loaded up with e.g. bags of dirt or something, but once you measure it in your typical configurations, you should be able to pretty closely estimate where it needs to be that day. Note that this is ambient temp, not hot after driving for 50 miles.

 

[Hellwig]

I’ve been running our ‘24 Platinum with stock tires at the recommended 39 psi cold (adjusting for temperature) for the last year. The ride is a little rough, but it is more truck than car. With the colder weather in Chicago the cold pressures have dropped to 37 cold and we’re noticing a more comfortable ride.

Has anyone tried a lower air pressure? Any negatives?

I wouldn’t tow at the lower pressures, but we take a long driving trip in the winter with a lot of highway driving and wouldn’t mind the extra comfort. Appreciate your thoughts.

I drive with under pressured tires too. It's not a big deal and it gives a lot comfortness. When I tow, I pump tires to 45psi and above.

 

[BrianDA]

I moved to the Expy from a Flex. It had 20" wheels with a more low profile tire, similar to the 22's on my Expy. I'd always found with the Flex that if I ran recommended pressure or a couple PSI lower I wore the shoulders quickly on the tires. Better ride but shortened tire life. If I ran them a couple of pounds higher, the tires wore evenly and lasted longer. I've had the Expy for coming up on 2 years and run the pressure about 2# higher and, with 45k miles on them, the tires look incredible. It all comes down to what you prefer more, longer tire life or more comfort. I lean toward tire life because I'm running 25k miles/year.

 

[chuck s]

I'd not sweat a couple PSI especially if the ride is better. This is based on some questionable Excel manipulation by me that indicates the recommended 35psi for my '17 XLT with OEM tire size is more than enough for the gross axle ratings and even 32psi will support more than the GAWR of either axle. Tire pressure and carrying capacity are NOT a lineal function but within the 30-50psi range of my tires are close enough.

Increasing rear tire pressure above the placard pressure can take some squirm out of P-metric radial tires when towing but didn't increase the GAWR and will simply make the ride harder during normal driving. Likewise putting LT (light truck) tires on a SUV will ruin the soft ride since they require higher pressure which is not noted on the data placard.

If you're getting abnormal tire wear take a look at Brian's experience.

Easiest solution? Run placard pressure all the time. It will handle everything.

-- Chuck