Why does ford recommend running 55psi in my front tires and 70 in the rear?

 

The only thing I could ever figure was in case you were carrying a lot of weight in the bed???

 

I run 55 all the way around on my 10-ply tires, not hauling or carrying anything, and get rather even wear all the way around. The 70 is not necessary unless you're really loaded up.

 

I think they want 70 in the rear because they presume you will be hauling something at sometime since you have this truck and the 55 in the front is adequate and will provide a more comfortable ride - they also want them rotated every 5,000 miles - which should keep the wear evened out.

I prefer to adjust the pressure to obtain even wear without having to rotate that often...on the other hand, taking the rims off the axle regularly will probably make them easier to get off when needed - I had to beat my rear rims off when rotating the first time so I cleaned and sprayed the rear hub of the wheels with WD-40 before remounting so they would come off easier the next time.

With my truck empty I'm presently running 75 front and 65 rear, which is up from 70 and 60, which is up from 65 and 55 - trying to squeeze out that fuel mileage (last hwy trip got 18.557 mpg) ... but, if I drove on rough roads, it'd definitely go back down. If I haul some substantial weight, I'll put 70 to 75 in the rear....

 

X2 on more pressure in the front! I run the full 80 with good wear and control, and I get up to 19.5 MPG on long hauls. The back can be lower when empty (the diesel is heavy), then bump it if you carry a load.

 

70psi..... gets better mpg...... rides like a log wagon

55psi..... lower mpg........ rides like a car (a big car)

 

Yeah guys I prefer mpg over riding like a caddy lol

 

Personally, I let my tread wear pattern dictate my pressure because I want the tires to last as long as possible while maintining as much ground contact as possible (traction) in the Southern frog-strangling thunderstorms we get around here.

As for ride comfort, the 55 psi pressure gives me a good situation as well. If my 20K miles per year were all highway or city/urban roadways, I might get better mileage at 60-65 on my fronts, but only at the expense of center-tread wear. Regardless, over half of my mileage is on narrow county back roads, half of which are regularly pot-holed and patched because of all the heavy log, chip, lumber, and bark trucks which are transported raw materials to either area lumber mills or paper mills. Given that, a lot of my 55 psi riding "like a big car" setup ends up more like a "log wagon" ride because of the road conditions. However, when I did try 55, 60, and 65 psi in the fronts on my old Revo's, I ended up getting [I]worse[I] mileage (due to higher front elevation and the subsequent loss of aerodynamics by running with the air dam in a higher and less efficient ground clearance position), noticeable increase in center tread wear, and an intolerably rough ride.

The center wear versus even wear issue is also going to be a function of the your driving speed while cornering, whether or not most of your travel is on long straight runs or lots of curvy roads. Additional factors include tire structure and sidewall strength, which will vary from brand-to-brand and model-to-model on tire specs, and will also be influenced by the side wall height. My ten-ply Michelin AT2's seem to have pretty stiff sidewalls, even though they are 285x75's on stock 16-inch rims (fairly tall sidewall height). I saw the same type of even wear pattern at 55 psi on the Bridgestone Revo's I ran (285x75 on the same stock rims).

Rules of thumb are just that... generalizations which are generally, but not always, true. There are other physical factors which often influence these generalizations.

Just one engineer's overly detailed perspective. I had a few extra minutes this morning to think about this issue perhaps more than I should have.

 

I generally run 80psi all the way around because 80% of my driving is with the 5th wheel hooked up.

 

I run 70 in the front - 80 in the rear - While towing -

 

I was running 55 in the front and 50 in the rear when I had my 36x14.5s on the truck. With my snow tires I run 52 and 48 all those are empty. If your more worried about tread wear then you should do a chaulk line test to make sure you have the right psi

 

A "get by" on the chalk line test is to simply look at the sandy dirt coverage on the tire tread when pulling up to a fuel pump immediately after running a while on a paved road. The sandy dirt coverage will tell you where you're making contact on the road, and will be fairly accurate since it gets created while running at a rather low speed for a very short distance.

 

Good tip there. I did the same thing (sanded road after snow melt) and verified the wear from my pressure settings.

 

"As for ride comfort, the 55 psi pressure gives me a good situation as well. If my 20K miles per year were all highway or city/urban roadways, I might get better mileage at 60-65 on my fronts, but only at the expense of center-tread wear. Regardless, over half of my mileage is on narrow county back roads, half of which are regularly pot-holed and patched because of all the heavy log, chip, lumber, and bark trucks which are transported raw materials to either area lumber mills or paper mills. Given that, a lot of my 55 psi riding "like a big car" setup ends up more like a "log wagon" ride because of the road conditions. However, when I did try 55, 60, and 65 psi in the fronts on my old Revo's, I ended up getting [i]worse[i] mileage (due to higher front elevation and the subsequent loss of aerodynamics by running with the air dam in a higher and less efficient ground clearance position), noticeable increase in center tread wear, and an intolerably rough ride."

F250_ , that is interesting about the aerodynamics ... I wouldn't have thought that a fraction of an inch would have made any measurable difference...

I did, however, go back down from 75 F and 65 R to 70 F and 60 R due to the harsh ride and I had also noted that the rear tires weren't touching on the edges ... may have lowered the front end about a 1/16 inch ... I'll check again to see what the rear looks like next time out - may go on down to 55 R......seems as though the factory recommendation should almost be reversed when not hauling!

 

Went on down to 55 in the rear and the very edges still show "clean"...so, gonna ease on down to 52 and drop the front down to 62 ... this should keep me in the 60 - 64 cold range for front and 50 - 54 cold range for the rear with ambient temperature fluctuation ... don't know if my conscience will let me, but I may even try it at the factory recommended 55 front and try 50 rear - unloaded, that is ... yep, gonna have to get me some chaulk!

Anybody other than F250_ running 55 or so in their 10 ply E load range tires with good results??