Help! tire psi question

Discussion in 'General RVing' started by Four Winds, Apr 6, 2005.

  1. Four Winds

    Four Winds Member

    I replaced my two front tires on a Four Winds 28A class C m/h. I had LT225/75R16 8 ply load range D @ 60 psi. The local goodyear dealer replaced them with LT225/75R16 10 ply load range E @ 90 psi. He said this was what the factory should have put on there in the first place. I called Four Winds Mfg,a local dealer that sells Four Winds,
    and the Uniroyal factory and could not get an answer. Does anyone know if 90 psi is a resonable psi for that condition? :question: :)
     
  2. Kirk

    Kirk Senior Member

    Help! tire psi question

    The answer to that is in the weight that you have on your RV. I would take it to a truck stop where you can get the weight of each axle, or better yet one of the rare ones that can give you the weight of each wheel. Truck tire and RV tire pressures that are porper are based upon the weight on each tire. You do want the same pressure in both sides of each axle and also both tires of a pair of duals. If you visit the tire manufacturer's site, there should be a chart for the particular tires that you have which will give the air pressure for each possible weight.

    In this way you can also see what the weight ratings for each tire is in the D and E grades and compart that to the gross weight rating of your motorhome. (GVWR). I suspect that your tire shop was just selling a more expensive tire, but with not weights or weight ratings for the motorhome it isn't possible to know for sure.
     
  3. helibob

    helibob New Member

    Help! tire psi question

    maximum weight and pressure are stamped on the tire somewhere.
    it will give weight &pressure for single and duel.
    don`t know for sure but 90psi sounds high to me.just put 6 michelin`s on cl a m/h pressure max at 80psi according to manf.
     
  4. Krazeehorse

    Krazeehorse New Member

    Help! tire psi question

    90 may be too much but the only thing you might suffer is premature wear in the center of the tread from "crowning". 70 or 75 is probably adequate for your vehicle. Everyone is correct when they say it depends on the weight on that tire. If you err to the negative side you will typically have sloppy handling, the tire runs hotter and wears faster, and in a worse case scenario the tire blows. So 10 pounds too much is much better than 10 pounds too little. It is very unlikely that you are going to feel the tires riding "harder" with the extra pressure either. I have load/inflation tables that I would be glad to get to you if want them. Krazee
     
  5. turnipbwc

    turnipbwc New Member

    Help! tire psi question

    You guys talking about tires got me wondering. The tires on my class b are LT225-75R-16 but only 2 ply. Do you think 2 ply is alright ? The plate on the door says 55 psi front, 80 psi rear.
    The GVWR is 8510.
    GAWR 3600 Front.
    GAWR 5360 Rear.
    turnip42
     
  6. Krazeehorse

    Krazeehorse New Member

    Help! tire psi question

    Look for the load range. They are only 2 ply construction in the sidewalls. They are heavy plies. There are additional plies (or belts) in the tread area that go from shoulder to shoulder. Somewhere you will see "load range" or LR followed by a letter. B=4, C=6, D=8, and E=10 and so on. Your LT (light truck)225/75R (radial)-16's are probably load range D's. This means that your tire is constructed in such a manner that it will safely carry the load of an old original 8 ply tire. And I would inflate them to the vehicle manufacturers specs (maybe 5psi more in the front).
    Krazee
     
  7. Poppa

    Poppa Member

    Help! tire psi question

    Going to stick my 2 cents in here.
    Vehicle weight has a lot to do with what tire pressure you run to a point.
    Weigh the front axle then look on the side of the tire, there wil be a max inflation pressure that will look like this. 90 psi 3,000 lbs.

    If your vehicle weight is 6,000 on the front axle then 90 psi would be correct. If it is somewhat less check with your local tire rep and see what pressure you should be running.
    Never go below the recommended pressure because your tires will run hot due to sidewall flex.
     

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