Tire pressure
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Lead Driver
Joined: Jan 2005
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From: Huntington Indiana
Tire pressure
OK running battle between the spouse and I. On the sidewall of tire it says MAX pressure 80psi but on door jam says use 65psi. I am going with the 65 and spouse says 80. Which is correct?
New tires just got put on and had 80K miles on old tires and worn perfect with 65psi.
New tires just got put on and had 80K miles on old tires and worn perfect with 65psi.
Senior User
Joined: Mar 2006
Posts: 366
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From: Fredericksburg, VA
The 80 PSI on the tire is the maximum allowable pressure for the tire. The 65 PSI recommended by Ford is for the best ride, however, that will vary with what load you may be carrying. On my F450, the tires are marked 110 PSI (they are 225/70R19.5 'G' rated); when empty I run 85 front and 75 rear and it runs great, with my 6,000 pound truck camper and boat on the hitch, I run 100 front and rear. If I ran the 100 PSI when empty, it would be like having steel tires. If you got 80K with the last set, then stay at that pressure!
Postmaster
Joined: Jan 2005
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From: Peoria, IL
Actually the door sticker is the correct pressure for your truck when loaded to max GVW. If you aren't loaded to max GVW you can run lower than the pressure on the door. Ford just recommends that pressure to cover their butt.
In order to figure out the correct tire pressure you need to weigh your truck and find out how much load is on each axle. You then take that load and use a tire inflation table to find the correct pressure for that load. However, if you ever increase your load, you need to adjust your tire pressure accordingly. Ford doesn't trust people to do that, so they recommend the tire pressure for Max GVW.
In order to figure out the correct tire pressure you need to weigh your truck and find out how much load is on each axle. You then take that load and use a tire inflation table to find the correct pressure for that load. However, if you ever increase your load, you need to adjust your tire pressure accordingly. Ford doesn't trust people to do that, so they recommend the tire pressure for Max GVW.
Senior User
Joined: Oct 2006
Posts: 215
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From: Allegheny Mountains, VA
Chalk test time!
Everyone who has posted above is exactally correct. To find that perfect unloaded "sweet spot" that Beerstalker is talking about above, I used the 'chalk test' to figure out what psi to run my 285/75/16 "D" BFG KOs at......55psi. Perfect for my truck.
Good luck.
Stone
Everyone who has posted above is exactally correct. To find that perfect unloaded "sweet spot" that Beerstalker is talking about above, I used the 'chalk test' to figure out what psi to run my 285/75/16 "D" BFG KOs at......55psi. Perfect for my truck.
Good luck.
Stone
Postmaster
Joined: Jan 2005
Posts: 4,743
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From: Peoria, IL
The chalk test mentioned works well on new tires, but if your tires are already worn down it will not be accurate.
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Senior User
Joined: Oct 2006
Posts: 215
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From: Allegheny Mountains, VA
This is how I do it:
Find a nice large slab of very level, clear and clean, pavement/blacktop. A walmart parking lot works good. I used a freashly paved YMCA parking lot after hours.
Get yourself a stick of 'playground chalk' that kids use to draw hop-scotch games on sidewalks with. It's the same as blackboard chalk, only it's about 1" in diameter and about 4" long. It's also normally a color other than white.
Now, park at one end of the parking lot with your tires pointed straight ahead. Take the chalk and color a large 3-4" swipe evenly across the entire width of the tire tread. Now, get in the truck and drive it in a straight line for 30-40 yards. Stop the truck, get out and look at the 3-4" swipe you just marked on your tire.
What you are looking for is even removal of the chalk from your tires. This also translates into even displacement of the chalk onto the pavement.
It is best to start out with your tires inflated to the "max" limit as marked on your tires. This will almost surely ensure that the chalk with not wear off evenly. It will rub off the chalk from the tread in the center of the tires, but not on the outside shoulders. Now, deflate your tires by 1-2 lbs (or more depending on how far away you are from even wear). Repeat the process again until you have even chalk removal.
Note: The pavement must be bone dry and it not be raining for this to work well.
You could start low and move up, but you do not see that 'sweet spot' as clearly when the tire goes from under-inflated to "just right" as when you go from over-inflated to "just right". Also, when you start to get close, you only want to deflate 1 lbs or so at a time. Yes, it does make a difference.
Oh, and get a good, trust worthy air pressure guage. I prefer the digital type.
This test works amazingly well, especially on big trucks with big tires. Made a world of difference in my tire wear, ride, and how she handles.
Stone
Find a nice large slab of very level, clear and clean, pavement/blacktop. A walmart parking lot works good. I used a freashly paved YMCA parking lot after hours.
Get yourself a stick of 'playground chalk' that kids use to draw hop-scotch games on sidewalks with. It's the same as blackboard chalk, only it's about 1" in diameter and about 4" long. It's also normally a color other than white.
Now, park at one end of the parking lot with your tires pointed straight ahead. Take the chalk and color a large 3-4" swipe evenly across the entire width of the tire tread. Now, get in the truck and drive it in a straight line for 30-40 yards. Stop the truck, get out and look at the 3-4" swipe you just marked on your tire.
What you are looking for is even removal of the chalk from your tires. This also translates into even displacement of the chalk onto the pavement.
It is best to start out with your tires inflated to the "max" limit as marked on your tires. This will almost surely ensure that the chalk with not wear off evenly. It will rub off the chalk from the tread in the center of the tires, but not on the outside shoulders. Now, deflate your tires by 1-2 lbs (or more depending on how far away you are from even wear). Repeat the process again until you have even chalk removal.
Note: The pavement must be bone dry and it not be raining for this to work well.
You could start low and move up, but you do not see that 'sweet spot' as clearly when the tire goes from under-inflated to "just right" as when you go from over-inflated to "just right". Also, when you start to get close, you only want to deflate 1 lbs or so at a time. Yes, it does make a difference.
Oh, and get a good, trust worthy air pressure guage. I prefer the digital type.
This test works amazingly well, especially on big trucks with big tires. Made a world of difference in my tire wear, ride, and how she handles.
Stone
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