Agreed 100% on all this ^^. The E150 wheels, along with being 15" had only 5 lugs per wheel, another indication that chassis was from from being a true motor home. Converters did the general buying public a huge disservice adding so much weight that also encouraged owners to essentially overload them full of people and cargo, thinking the suspension and tires could safely handle those loads.

While I never really think about MPG's recent half-assed calculations show I'm about 15 MPG which is better than I originally thought. Along with other possible fuel-saving practices the higher tire pressure certainly doesn't hurt.

 

I suppose my original worry was that if I use too much pressure, there is less tire in contact with the road, thereby making it easier to skid or loose control.

Do I understand correctly that if I have, for example, a 5000 pound vehicle, and 40psi in the tires, I will have 5000/40 = 125 square inches of tire on contact with the ground. If I increase the tire pressure to 50 psi, I then only have 5000/50 = 100 square inches of tire in contact with the ground.

I think this simplification ignores the stiffness of the sidewall.


Les

 

There are other factors at play but basic physics friction equations are based on load and coefficient of friction. Contact area is not a factor. I don't know then why wide tires are more difficult to steer at a standstill than narrow tires absent power steering.

Sixto
93 E150 Chateau 5.8 191K miles

 

You're over complicating this as well. 51 psi might be fine fully loaded, but you'll find the ride somewhat harsher than running the tires 10-15 psi lower if not fully loaded. Handling ? run what you feel comfortable with. Practice makes perfect. Don't worry about trying to figure the answer out using a calculator, you'll never get the answer you think you're looking for that way. Drive it with different pressure levels then stick with what feels right to you.

 

What are you more concerned with, ride or tire wear, my 99 E350 suggests 60 PSI, the tire max is 80 PSI, when my tires are below 80 PSI you see visible wear on the fronts, it's due to running I-beams, but at max they wear even. I have seen the argument and will no longer play in it, you can see it for yourself but it is common with vehicles that have I-beams, fully inflated verse partially inflated, you will be lucky to get 30,000 miles from a set of tires if you drop pressure for a better ride, as suggested by the factory.

 

I am concerned with safety. Ride or tire life are both secondary.

 

Well, if you think running tires under inflated is safe, go for it!

 

I don't know what is safe, that is why I am asking for advice.

 

10 psi under is perfectly safe. (41 vs 51) as well 15 psi under may be too. That is why I suggested you try different levels and DRIVE it to see what you're comfortable with. And I'm saying this as a truck driver with well over 4 million miles behind him, in all types of vehicles, in all kinds of weather. That kind of experience you will not find using a calculator.