Tire Pressure

I have a 2500 Ram Pick up.The recommended rear tire pressure is 70 psi.The tires can take up to 80 psi.When the truck is not loaded or carrying my 11,000 lb 5th wheel.Could I get a softer and safe ride if I reduce the rear tire pressure to 55 psi?


Absolutely not.

If the vehicle mfr specified 70 psi in the rear tires when the loadbed is unladen, you would be very foolish to use a lower pressure.

I disagree…The recommended tire pressure was meant to accommodate the maximum load the vehicle can carry…When being driven unloaded, 35-40 psi will support the empty truck and deliver a MUCH smoother ride…Be sure to remember to adjust tire pressure when changing the load on the vehicle…

Go to www.michelinrvtires.com. You need to get their load and inflation tables. You can get your axle weighed at a truck stop for only a few dollars. If you can’t get your rear tires only on the platform, then weigh the rear axle and the trailer. Then weigh the trailer and subtract that from the first reading. This assumes that the rear wheels on each side of your pickup support equal weights and they probably do.

Check the door label or the owner’s manual again. It probably gives two values for tire pressure – perhaps 70 psi when loaded but maybe 35 psi when unloaded.

Here’s the problem.

If the vehicle tire placard specifies a single set of pressures, then the pressure is for a fully loaded vehicle. That means the vehicle manufacturer tested the vehicle at both conditions with that pressure - both loaded and completely empty.

So if you use a lower pressure (because the vehicle is empty), you’re doing something that wasn’t tested and that may be a dangerous condition. A tire’s spring rate is pretty much dependent on inflation pressure - it varies only a little from tire to tire (at least comopared to the spring rate caused by inflation pressure). A vehicle’s shock damping, spring rate, and sway bar spring rates were specified by the vehicle manufacturer based on the pressure listed on the vehicle tire placard. The only way to be sure there isn’;t a problem is to conduct a whole series of tests at that condition - which means destroying at least one set of tires.

Also, I would be very careful selecting a pressure without a thorough research of what the vehicle weighs when unladen. Blanket statements such as “35 to 40 psi” is not only highly speculative, but probably incorrect. Even if you use the tire load tables, you need to be aware that those tables are maximums, not recommendations. It is always good engineering practice to over-specify - and in this case, to use MORE pressure than the table indicates.

However, if the vehicle manufacturer says something different about tire inflation pressure for unloaded conditions (like in the owner’s manual), you can be sure they tested that and found it to be acceptable.

Thanks to every one for thier comments.I will have to rethink my tire pressures.

The only other thing to check is your owners manual, maybe it has some advice on this. But I imagine everything is on the placard.

You’re not going to get much of a smooth ride with LT tires. The sidewalls are stiffer than P tires, and ride comfort suffers. However, P tires are not recommended for this truck, as they cannot handle the load rating.