How much PSI are you running in your tires?

120 steer 105 drive 110 trailer

 

Our idiot parts changer in the shop insists 80 psi on the drives is enough. He says the tire salesman, the one who literally makes his money selling as many tires as possible, told him so. Think he might have an ulterior motive? We run 80-84k when loaded. I insist on 120 psi for the wear and fuel mileage.

My question is how much fuel mileage loss does one suffer with under inflated tires?

 

This should be fun. 95psi steer, 90 drives and trailers.

 

110 steers, 100 drives. It's what the door sticker recommend.

Fed Ex runs 85 in their trailers.

 

As little as I understand - the worst problems are caused by heat.

Sidewall flex.
Summer temps
Higher speed.

I never run recaps. I’ve never had one blow.

 

Definitely, Michelin had a really good video out years ago on aircraft tires. Basically with every reduction in PSI
Below recommended coupled with the weight of aircraft, caused a certain increase in tire temperature, the lower PSI caused the sidewall to flex, allowing the sidewall to break-down, increasing the temps allowing air between the plies resulting in a weakened sidewall eventually resulting in a blown tire. Basically the tire returns back to its original properties.

I used to have the video as I used it at a Safety stand down in Mexico years ago. Same principal applies to any ties. Especially those with rigid sidewalls designed to carry weight.

 

Lately we've been running right around 100 on steers and 95ish on drives. Came down 10psi on steers and I can tell the difference. Rides better on these awesome NE roads

 

Just remember, max psi is for max load. What about when your empty? I agree and understand max inflation psi is better for mileage. But not the best for wear or ride. Have to realize a tire is part of the suspension and effect ride quality. Find a happy medium. 110 cold inflation is way over max psi under a load on 100° day.


I do what works for me. Just took Michelin energy of at a 150k miles with 13/32 still on tread. Only have one dropped tread area. Im giving credit to a monroe shock that didn't last 3 months. They are legal and would run out on a trailer a long time. But off my steers for age. They have 200k plus in them. Never been over 95 psi. I have been known to move some pounds too.

 

To be accurate you need the load and inflation table for your particular tires.
Psi varies with weight. That is the actual correct answer.
I run Michelin on all 5 axles 110 steers based on my weight I average on that axle
100 on drives based on average weight I run
Trl 100 lbs based on inflation table based on my average weight. No I do not adjust for heavier or lighter weights.
But tires last and with Centramatics on all 5 axles and tire rotations every 100k

 

My next steer tires are 12R’s or 295/80/22.5.

Been noticing the weight of the big kitty, steel cab, sleeper and double frame is wearing the steers down on the outside edges.