Who runs 285/75/16s on the factory 16x6.5 HD wheels?

Discussion in 'Tow & Trailer' started by DPI, Jan 12, 2005.

  1. DPI

    DPI 1/2 ton status

    Jun 22, 2000
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    In the Burbs close to Tulsa, OK
    The tires on my tow rig are nearly bald in the center tread of the tire. They are 285/75/16 mounted on the factory aluminum wheels. The manual calls for 80 psi in the tires, however the spec'ed tire is a 245/75/16. I aired down the tires to around 34-36 psi which should stop the weird tire wear, but will it handle a loaded trailer?

    I am in a prediciment. I need new tires, but want to make sure the 285's will work OK with the 6.5" wheels.
  2. 6.2Blazer

    6.2Blazer 1/2 ton status

    Feb 24, 2000
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    You have set the tire pressure according to the weight of the vehicle......a set of 235/85's at 80 psi would wear the center of the tread also when run under an emptly truck.

    For example, I have an '03 2500HD that had the stock 245/75R16 (E-rated, 80 psi max. pressure) tires which were set at 80 psi from the factory. The rear tires, which obviously had very light weight on them with an empty bed, started showing noticable wear on the center of the tread after about 10,000 miles. I rotated the tires front to back and adjusted the rears to about 45 psi while running empty (which is the vast majority of the miles) which then showed pretty even wear up to the tires being completely worn out at around 40k. I typically kept the fronts set around 60-65 psi.

    When I hooked up my 8,500 lb. trailer I adjusted the rear tires to up around 70 psi in order to deal with the increased weight on them and to give a little more firm handling. The fronts stay around 60 with the trailer simply because there is no added weight on them....it's actually a little lighter on the front with the trailer attached.

    Chevy will recommend 80 psi, which is the maximum rated pressure of the OEM tires, because that is the safest pressure when hauling really heavy loads. Even though the tires will wear and handle better a much lower pressure when the truck is empty, they won't recommend that because of liability issues......i.e. somebody overloading their truck and having a blow-out because they only had 40 psi in the tires.

    Now to go on with this discussion, you have to remember that 80 psi is only an arbritrary number.......meaning the pressure depends on the particuliar tire you have (size, load range, etc....). If need to look at the sidewall of the tire to see what the maximum load and pressure is. Here are some examples from my truck:

    OEM tires - LT245/75R16, load range "E", max. load of 3,000 lbs. @ 80 psi
    new tires - LT265/75R16, load range "D", max. load of 3,000 lbs. @ 65 psi

    As you can see, even though the 265's are a lower load rating and have a lower max. pressure, they still are rated for the exact same max. load. (This is very common since a larger tire has a larger volume and thus can support more at a lower pressure.) I can no longer go by either the manufacturer's recommendations, or by what pressures worked in the OEM tires, because we are dealing with a different load curve now. Also, if I were to put 80 psi into my 265's, which are only rated at 65 psi, I would be risking a tire blowout because of the excess pressure.....especially if I were hauling a heavy load for long distances on a hot day because the pressure increases even more with heat.

    The load capacity of a tire vs. pressure, while not exactly, is pretty close to a linear scale. Meaning if a tire is rated at 3,000 lbs. @ 80 psi, then it is pretty close to 1,500 lbs. @ 40 psi.

    Think about that for a second. If you have four tires with a max. load of 3,000 lbs. each that means they can support 12,000 lbs. That's higher than the GVWR of any regular SRW truck that I know of. An empty fullsize truck weighs what, maybe 6-7,000 lbs.? With the front weight bias of a diesel truck you may only have 2,500 lbs. over the rear wheels when empty.......so why do you need 80 psi, and corresponding 6,000 lb. capacity, in the rear tires with no load?

    With all that babbling over with, my recommendation would be to play around with the pressures and find something that provides a decent ride and wear when empty, and then increase the pressure whenever you are towing. To be on the safe side while towing, you can go up to the maximum pressure as stated on the sidewall of the tire.

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