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  1. #1

    Default Tire pressure front/rear differences

    This issue is what brought me to the forum and I wanted to get the info out there. I had several chats with GM and Goodyear (maker of tires on my 2012 Silverado 2500 HD diesel). I pull a pretty big travel trailer and use a load stabilizing hitch which transfers much of the weight back to the front axle. With the door sill sticker saying 60psi front, 75psi rear and Goodyear saying 80psi for the E rated tires, I wanted to know from GM why, and if that inflation guide was for empty truck as well as heavy load. Got a call from GM saying their pressures were based on smooth ride and tire wear. I questioned the greater psi on the rear where there was less weight. Answer the same: ride and tire life. Asked what about my situation where I'm transferring much of the load back to the front and should I not pump the front up some when towing. Answer: same psi in all situations--60 and 75. So I called Goodyear, maker of the 265/60 R20s , E rated, 80 psi and asked them if they agreed with GM even though the max load on the tires is obtained at 80psi. Answer: inflate according to GM guidelines. So, finally, I asked the correct question which was to send me the data on max load for these tires at GMs reduced pressures. Walla, 60 psi, for these tires gives you a load limit of 2660# per tire. 75 psi max load equals 3110# per tire. Guess what, max front axle weight on my 2500 HD is 5200# and the rear is 6200#. Since it takes both the left and right to carry the axle, that's tires inflated to carry a little over 5200# on the front and 6200# over the rear. In other words smooth ride and tread wear have little or nothing to do with it. GM is just not going to recommend tire inflation that allows the tires to carry more than the axles. My guess, it's a liability thing more than anything. So, I'm going back to what has worked very well with ride and wear especially when towing. 72psi or so in the rear and a little less in the front (Texas summer heat, where i tow, will push the rears up 10 degrees if driving 70). Note: Goodyear will send info on "load limits at various inflation pressures" for various tires from The Tire and Rim Association, Inc. if asked.

    Howard

  2. #2
    Legend

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    on the tire pressures . this is a variable amount depending on load and the tires MAX PSI rating.

    since you tow at times a large trailer then also have no load you must vary the tire pressures to allow the tire to support the load properly. too much air poor control and abs stopping issues also tread wear is in the middle treads. too little air the tires heat up wear rapidly esp. at the shoulders.MPG will drop.

    I place white marker on the tire tread drive about 20 ft then observe how the white marker has worn then adjust the pressure for an even wear out to the outer tire edges about one inch in.then test drive.

    max pressure gives max tire load but with no load this causes control issues esp on poorly paved road.

    On my 1500 truck I have load C tires 50 PSI MAX. I have found 50 psi in the front tires gives even wear. on the rear I found 43 psi with no load. when I tow I increase the rear pressures to 48psi this is a 4500lb boat trailer 2 axle.

    tires wear so even they all have the same wear acroos the entire tread. I get 90,000mi on them and I rotate 13,000mi.

  3. #3

    Default

    Im with you 100%, j cat. When I got the same answer on psi for all load conditions and no real answer to why rear 15 psi more than the front, I knew it had to be something other than smooth ride and tire wear as stated. Not until Goodyear sent the tire load limits at various inflation pressures did I realize GM was just recommending a psi to match their front and rear GAWR. For loaded safety, it does not really matter as the recommended pressures are plenty for any load the truck can carry, just misinformation as to why. And, I believe these pressures will not result in the best wear when running empty, but that is only my guess. I'll get out the white chalk.

  4. #4
    Legend

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    with my 1500 load C tires the GM sticker says 50psi front rear. this is to cover ,,,as you stated the MAX vehicle loading.. with no extra loading you have to tweek the pressures to an amount that will create good tire tread contact to the road but no so much that your creating too much friction.

    I only purchased 1 set of tires got 140,ooomi on vehicle now..taking the time to get this pressure correct saves money.

    If I go to load E tires [hard to find C load tires] I will have to drop down to a much lower pressure than 80 psi.....

  5. #5
    Master Mechanic silverhobey's Avatar
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    thanks for getting all of the info that you researched....this thread is a great
    read ....Brian
    Silverado Crew.....4.8 L

    ---Pendaliner BoxLiner and Side Rails....Van and Truck World
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    ---AVS Window VentVisors...Canadian Tire
    ---AVS tinted License plate covers....Wal-Mart

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