Tires Contact Patterned ?
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Joined: Jun 2007
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Tires Contact Patterned ?
After running 2k on the new Michelin LTX-M/S I decided to pattern them for tire pressure. The tires are size 285/75R16D and the truck is a ’03 F250, 6.0L XL, CC, LB, and <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com
ffice:smarttags" /><st1:stockticker>SRW</st1:stockticker>.
I started out with 45 psi front and 40 psi rear; I painted (white latex, 1-1/2wide foam roller) a white stripe across each tire. I drove, as straight as possible, up and down a few of our city blocks and observed the paint strip. With the truck empty (except for me and a full tank) the rear tires wore the paint off except for about 3/4 inch of paint on each outside of the tire. The front looked good with only a little paint on the outside treads. I continued to let air out of the rear and checking the wear. I’m now down to 23 psi in the rear and about a 1/2 inch of paint still remains on the outside. I’m hesitating too drop the rear any further for city and highway driving.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o
></o>
<o> </o>
I’m going to run (empty) 40 psi front and 30 psi rear, keeping an eye on the tire wear and the fuel mileage and going from there. Tomorrow I’ll put the quad in the back and do it again to see what pressure is needed.<o></o>
<o> </o>
Any thoughts?<o></o>
ffice:smarttags" /><st1:stockticker>SRW</st1:stockticker>. I started out with 45 psi front and 40 psi rear; I painted (white latex, 1-1/2wide foam roller) a white stripe across each tire. I drove, as straight as possible, up and down a few of our city blocks and observed the paint strip. With the truck empty (except for me and a full tank) the rear tires wore the paint off except for about 3/4 inch of paint on each outside of the tire. The front looked good with only a little paint on the outside treads. I continued to let air out of the rear and checking the wear. I’m now down to 23 psi in the rear and about a 1/2 inch of paint still remains on the outside. I’m hesitating too drop the rear any further for city and highway driving.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
fficeffice" /><o></o><o
> </o>I’m going to run (empty) 40 psi front and 30 psi rear, keeping an eye on the tire wear and the fuel mileage and going from there. Tomorrow I’ll put the quad in the back and do it again to see what pressure is needed.<o
></o><o
> </o>Any thoughts?<o
></o>
Hotshot
Joined: Mar 2007
Posts: 10,101
Likes: 40
From: Pa
I think your pressures are way low and bad idea. I have the same size tires on my 04' 6.8l SC SB. I run around 48-50 in the back and 58-60 up front empty. There are many negatives to running tire pressures that are too low, especially on a heavy truck. Rotate the tires often and they will wear even.
Hotshot
Joined: Dec 2006
Posts: 14,069
Likes: 17
From: Melbourne, Ky
I've got 265/75R16's on my truck, an 02 F250 PSD, and I have 70 in the front and 55 in the rear. I'm sure with a tire a little bigger, you can run a little less air, but you are too low, in my opinion. If you run tire pressure too low, what happens is the sidewalls flex too much, weakening the steel belts, causing heat to build up, and causing tire failure. Underflation will cause problems more often then overinflation.
Senior User
Joined: Dec 2007
Posts: 363
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From: Raleigh, NC
Wheel width will make a difference on this too. If you are running a narrow wheel the tires will only wear center tread at any safe pressure. If you run them till they show whole tread pattern you are risking a blowout on the highway big time.
Postmaster
Joined: Jan 2005
Posts: 4,743
Likes: 3
From: Peoria, IL
45 front and 40 rear probably aren't all that far off. You really need to take your truck to a scale with it's normal everyday load (including normal passenger load) and figure out what your front and rear axle weights are. Then you can use the tire inflation table to figure out the correct pressures for that load (divide axle weight by 2 to get the load on each tire).
A 285/75R16 tire on a single rear wheel truck should run the following pressures for each weight. (PSI/LBS)
35/2130
40/2340
45/2540
50/2755
55/2925
60/3110
65/3305
So as you can see you don't need to be running 60psi in your tires unless that axle is loaded to 6220lbs. I highly doubt your axle weight is that high.
A 285/75R16 tire on a single rear wheel truck should run the following pressures for each weight. (PSI/LBS)
35/2130
40/2340
45/2540
50/2755
55/2925
60/3110
65/3305
So as you can see you don't need to be running 60psi in your tires unless that axle is loaded to 6220lbs. I highly doubt your axle weight is that high.
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Beerstalker, thanks for the pressure/load table. I had the truck weighted last year with full fuel and me, which is 90% of my typical driving load. It weighed 4800# front and 3100# rear, which is close to right as the PA Turn Pike gets me for a class 2 (8000#) if I have anyone else in the truck with me.
That being said, I’m currently running 48 psi front and 40 psi rear. I may now drop it to 45 psi front and 35 psi rear.
Back in the day I had a ’66 F-100 with 44” gumbo monster mudder tires on it and I ran 20 psi front and 15 psi rear, that however was a different weight, tire and time!
Thanks again, Steve
That being said, I’m currently running 48 psi front and 40 psi rear. I may now drop it to 45 psi front and 35 psi rear.
Back in the day I had a ’66 F-100 with 44” gumbo monster mudder tires on it and I ran 20 psi front and 15 psi rear, that however was a different weight, tire and time!
Thanks again, Steve
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