Lowering TV tire pressures

CapriRacer wrote:
Just an FYI:

I spent 5 years as the technical liason from a major tire manufacturer to Ford - calling on the light truck folks.

They test their vans, pickups, and SUV's both fully loaded and empty at the specified pressures (the ones on the door placard) for both ride quality and handling. They adjust the springs, shocks, and sway bars to get the vehicle to behave benignly at both conditions - that way the consumer gets a vehicle they don't have to adjust the tire pressures to be confident the vehicle won't misbehave in emergency manuvers and has a reasonable ride quality.

They also tested their trucks pulling trailers at the rated towing capacity.

I assume that other vehicle manufacturers do the same.

So I am confident that using the pressure specified on the vehicle tire placard is what they had in mind for both fully loaded and empty vehicles - unless they specify otherwise in the owners manual.

I can tell you that my 2001.5 RAM was a bit scary with 80 in the rear tires empty. And it came with a inflation document that had full load and partial load inflation numbers for both the LT245/75R16E and optional LT265/75R16E that I had.

And I invite you to stop by this winter while we are in Arizona and I will let you drive my 2015 RAM 3500 CC SB 4x4 with the rears at 80 PSI and the 43 PSI I set them at the other day. Then you can try to tell me the ride and handling to comparable.

From my 2015 RAM owners manual:

• Over-inflation reduces a tire’s ability to cushion
shock. Objects on the road and chuckholes can
cause damage that result in tire failure.

So if the rear axle on my truck weights around 3000 lbs empty and the tires at 80 are rate to 3640 x 2 = 7280, having them at 2x+ the actual load to me would unquestionably indicate an over-inflation issue.

So does not the owners manual have inherent conflicts in it's statements?

So my conclusion is the trucks manufacture's legal department had more input to the tire placard than the engineering department. It is call CYA.

If someone wants to bang their brains out all winter driving around with 80 lbs in their rear tires so be it, however it is not for me.