Originally Posted By: hattaresguy
35-40 psi is fine, if you inflate them to much the truck will ride like [censored].
I run the E's on my half ton at 40psi since day one and have never had any unusual wear or temperature increases.
If I was carrying a lot of weight on the highway like 1,500 in the bed I'd inflate them a bit more, that's where heat is generated. I'd probably run 60 in the rear.
If that is the factory spec for P-rated tires for your application you are running your tires potentially dangerously underinflated as you have reduced their load carrying capacity below stock spec for the vehicle.
See this document for details:
http://www.toyotires.ca/sites/default/files/loadinflationtable.pdf
Page 71 shows the following:
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O.E. Information (Obtained from the T.I.P.):
Vehicle: 2006 Ford F-150 XLT 4X4 Super Crew Cab
Tire Size (Front/Rear): P255/70R17 110S Rim width = 7.5”
Inflation Pressure (Front/Rear) = 35 psi
Using the TRA Load Inflation Table (see Table 8), at the O.E. pressure of 35 psi, the P255/70R17 has a
load-carrying capacity of 2337 lbs. As this tire has been derated by the vehicle manufacturer by a factor
of 1.10 to account for its installation on a light truck, the actual load-carrying capacity is 2125 lbs.
After confirming that the O.E. rim width is within the allowable rim width range for LT265/70R17 121S
E/10, refer to the TRA LT Load Inflation Table. The ‘Single’ load values apply, and this tire requires an
inflation pressure of 45 psi (2255 lbs.) to maintain adequate load capacity.
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At 35psi, the (larger width) LT tire above has a capacity of 235lbs less than the stock P-Metric tire. That is a reduction of 940lbs in carrying capacity for all four tires.
Now, for example, if I look up the stock tire size in the TRA chart shown later in the document, it shows a P265/70/17 LI 113 has a load capacity of 2,535lbs at 32psi. That is also what is shown when I look up the Michelin LTX MS/2 on TireRack. So, we reduce by a factor of 1.1 because it is a truck and we get a capacity of 2,304lbs.
I then scroll down to the LT section and look up the same size. LT265/70/17 has a capacity of 1,890lbs at 35psi. At 40PSI it is 2,070, at 45psi it is 2,255lbs and at 50psi we finally overtake the stock P-metric capacity and arrive at 2,470lbs.
So, using the derated P-Metric figure, the 4 stock tires give us a total weight carrying capacity of 4,608lbs per axle. Depending on how you are loaded will of course determine your distance from that figure. Using 35psi in the LT tire we reduce that capacity to 3,780lbs, a reduction of 828lbs of capacity per axle.
So my question to you is why are you running LT tires underinflated, reducing the load carrying capacity of the vehicle, rather than just running the correct P-Metric tire at stock pressure? (I am assuming your 1/2 ton doesn't call for something like a C-rated LT tire and rather a P-Metric) I found zero benefit from the LT tires on the Expedition, they were what the PO had put on and they were replaced with the correct tires. It isn't like with my F-250 where it actually called for LT tires and had the different loaded weights on the placard indicating what to run for pressure depending on what was in the bed. Your 1/2 ton truck doesn't have the carrying capacity to warrant an E-range tire, if it did, it would call for one. So either you are loading the vehicle up to levels it was not designed to carry, requiring a tire of that load range resulting in an unsafe vehicle or there is really no point in them being on there, which is why you are running them at the P-metric pressure, which, ironically, makes them a poorer choice in terms of carrying capacity than the stock P-Metric tires it calls for and is also potentially unsafe
If there's some compelling reason to running load range E tires on a vehicle that cannot utilize their capacity, please enlighten me.
