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Re: tire pressure

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  • malabar13@hotmail.com
    Hi J./C. Well that is a good question, but fairly easy. First the info. you have is for tires 7.50x16D. That is not here anymore but new and improved tires
    Message 1 of 13 , Oct 1, 2001
      Hi J./C. Well that is a good question, but fairly easy. First the
      info. you have is for tires 7.50x16D. That is not here anymore but
      new and improved tires today (?). If the tires on the rig is the
      correct load bearing, and only a good tire store knows, then follow
      the pressure marked on the tire. That is recommended tire pressure
      by them to perform well, within their limits. If you use the old
      standards, was for 7.50x16d, that was for that tire. The Chassis
      does not know what tires you put on. Also you might put on larger
      type tires -- wider tread -- and larger load. The bigger the
      better. One thing I learned was if you put a larger tire on in the
      rear , they wear longer and they sit higher and because they are
      bigger in the round you get better gas milage. The tire does not go
      around as much. You travel further with less turns of the tire.
      That is a ratio math. item !!!! anyway follow the tire company and
      that keeps the warr. up, in case something happens to the tires.
      dave costa --1984 El Dorado, Class A, Isuzu dingy.

      In classicrv@y..., jwelles@a... wrote:
      > We are new to the list and just purchased a 1984 Suncrest 27
      foot RV
      > It is a GMC with a 454 Chevy motor.
      > Here is our question;
      > The tag on the vehicle says GVWR 12,300
      > GAWR front 4880
      > 7.50x16D
      > 16x6K rims
      > 60 PSI cold
      >
      > GAWR rear 7500
      > 7.50x16D
      > 16x6K rims
      > 50 PSI cold
      > dual
      > On the tires it says max weight and then 80 PSI cold
      > How do we know what pressure to put in the tires?
      > Does the pressure stamped on the tire mean the maximum it will
      hold?
      > I have seen RV people who have 100 psi and we are wondering if
      ours at
      > 50 rear and 60 front are too low.
      > Thank you for your help in figuring this out.
      > John and
      Cindy
      >
      >
      >
      >
      > [Non-text portions of this message have been removed]
    • Bill Combs
      ... Inflated as specified, your tires are rated to carry: front: 2440 lbs each - this is the maximum load rear: 1930 lbs each (assuming duals) - max 2140 lbs @
      Message 2 of 13 , Oct 1, 2001
        > on 9/30/01 12:09 PM, jwelles@...@... wrote:

        > We are new to the list and just purchased a 1984 Suncrest 27 foot RV
        > It is a GMC with a 454 Chevy motor.
        > Here is our question;
        > The tag on the vehicle says GVWR 12,300
        > GAWR front 4880
        > 7.50x16D
        > 16x6K rims
        > 60 PSI cold
        >
        > GAWR rear 7500
        > 7.50x16D
        > 16x6K rims
        > 50 PSI cold
        > dual
        > On the tires it says max weight and then 80 PSI cold
        > How do we know what pressure to put in the tires?
        > Does the pressure stamped on the tire mean the maximum it will hold?
        > I have seen RV people who have 100 psi and we are wondering if ours at
        > 50 rear and 60 front are too low.
        > Thank you for your help in figuring this out.
        > John and Cindy

        Inflated as specified, your tires are rated to carry:
        front: 2440 lbs each - this is the maximum load
        rear: 1930 lbs each (assuming duals) - max 2140 lbs @ 60 psi

        Truck tires (that's us) should always be inflated to a pressure determined
        by the load the tire is carrying. The intent is to yield the most
        advantageous combination of tire wear, ride comfort, and handling. Over
        inflation can be OK -- i.e., is safe if not good -- but under inflation is
        *never* OK.

        To do it right, you must weigh your rig with the load you intend to go down
        the road with. A total of four separate weights (any 4 of front, rear, left,
        right, total) is necessary to determine individual wheel loading, unless
        you're lucky enough to have access to equipment to weigh each corner
        individually. Generally, keep side-to-side pressures equal in the front and
        rear, and arrange your load so that side-to-side weights differ by as little
        as possible, using the higher figure to determine inflation. It is common to
        add 4 psi to nominal pressures for extended, high speed (above 60 mph)
        highway driving. All pressures are, of course, for cold tires. Dual wheels
        can be inflated to the same pressure, but there is a school of thought that
        the inners should be inflated to approx 5 psi less than the outers.

        The nominal pressure should be taken from a load/inflation chart for the
        tire size in question. All brands are generally the same except for
        Michelin, which publishes its own tables. Tables can be found in most RV
        Repair/Maintenance manuals. I haven't seen any on the Internet, but then I
        haven't looked lately.

        Don't bother to ask most tire dealers about this unless you're immune to BS;
        they usually don't even know what you're talking about.
        --
        Regards,
        Bill Combs <ttursine@...>
        http://home.earthlink.net/~ttursine
        --
        "There's nothing wrong with this man
        that modern medicine and expensive
        surgery can't prolong."
        - Monty Python's Flying Circus
      • bobalou1@prodigy.net
        THE REAL DEAL!!! 1 Ford Explorers flip over and people sue Ford. 2 Ford states the tires are blowing out and then sues Firestone. 3 Firestone sues Ford,
        Message 3 of 13 , Oct 1, 2001
          THE REAL DEAL!!!

          1 Ford Explorers flip over and people sue Ford.

          2 Ford states the tires are blowing out and then sues Firestone.

          3 Firestone sues Ford, stating that Ford recommends a tire pressure
          too low and the tires are over heating thus causing the blow-outs.

          Ford and all other auto/Rv companies want their vehicle's to
          ride better than the competition. By lowering the inflation numbers
          (using the stickers) it softens the tires thus giving the vehicle a
          better ride (bumps only). Put the tire pressure at the recommended
          pressure on the sidewall of the tire and it may shake the fillings or
          false teeth out of your mouth if your vehicle is not up to that
          weight. Your steering wheel might be bouncing like a basketball even
          in a Cadillac.


          TIRE FACTS!!!

          1 The normal auto tire will gain or lose 1 psi for every 12 degrees
          of temperature. Your RV will gain or lose 1 1/2 or 2 psi for every 12
          degrees depending on the size of the tire. They are bigger than an
          auto tire and they have more air in them!

          2 The cold pressure is considered whatever temp it is outside. At 30
          degrees a tire should have 30 psi (example) just like at 90 degrees a
          tire should have 30 psi (example). If you have 30 psi in your tire on
          a 30 degree morning and the temp goes up 60 degrees to 90 by
          afternoon your auto tire pressure will be up about 6 or 7 psi your RV
          tires might be up 12 or 14 psi. Try to think about how a hot air
          baloon is able to fly. The air is heated to expand it, in your tire
          as it is heated it can only expand so far, so since it can't expand
          the pressure raises.

          WHAT'S THE ANSWER???

          This is not a black and white issue, DON'T USE JUST ONE SET OF
          NUMBERS OR THE OTHER! These numbers are only recommendations!!! The
          tire numbers are the max suggested psi for the weight on the tire!
          The stickers are manfacture suggestions for the vehicle, remember
          they want you to ride softly and buy another vehicle whatever it may
          be.
          I SUGGEST YOU SPLIT THE DIFFERENCE between the vehicle
          manfactuer sticker and the tire manfacturer. Remember water weighs
          about 7 pounds per gallon. Gas weighs about 6 3/4 pounds per gallon.
          4 friends weight about 600 pounds. 4 football players that are
          friends can weigh 1200 pounds. SO HOW MUCH WEIGT IS ON YOUR TIRES? It
          changes with every mile or fill-up. Play the middle of the road and
          you won't go bad. If your tires say 100 psi and your chassis sticker
          says 80 psi and you set your tire pressure at 90 psi you have it
          covered. Low on water and fuel or fully loaded with football players.
          Any other problems see a good repair person, IF THEY CAN'T FIX IT GET
          YOUR MONEY BACK!!!!


          I don't work for Ford or Firestone, Bob.

          P.S. Can we get spell check on this site?
        • Bill Combs
          ... Sorry, but in a small percentage of circumstances this can result in under-inflation, which is dangerous. An overloaded tire is not your friend and may
          Message 4 of 13 , Oct 1, 2001
            > on 10/1/01 7:53 PM, bobalou1@...1@... wrote:

            > I SUGGEST YOU SPLIT THE DIFFERENCE between the vehicle
            > manfactuer sticker and the tire manfacturer. Remember water weighs
            > about 7 pounds per gallon. Gas weighs about 6 3/4 pounds per gallon.
            > 4 friends weight about 600 pounds. 4 football players that are
            > friends can weigh 1200 pounds. SO HOW MUCH WEIGT IS ON YOUR TIRES? It
            > changes with every mile or fill-up. Play the middle of the road and
            > you won't go bad. If your tires say 100 psi and your chassis sticker
            > says 80 psi and you set your tire pressure at 90 psi you have it
            > covered. Low on water and fuel or fully loaded with football players.
            > Any other problems see a good repair person, IF THEY CAN'T FIX IT GET
            > YOUR MONEY BACK!!!!

            Sorry, but in a small percentage of circumstances this can result in
            under-inflation, which is dangerous. An overloaded tire is not your friend
            and may self-destruct. If you're running at or above the GVWR -- got too
            much stuff! :-) -- and the recommendations are on the low end, the tires
            could be overloaded.

            Admittedly not a *real* common situation, but it would apply, for example,
            to my rig if the recommendations were in the lower half of the tire's usable
            range. I *definitely* got too much stuff. (Fortunately, I also have an extra
            leaf in each spring and enough extra capacity in the running gear.)

            Safest way is to weigh the rig and proceed from there.
            --
            Regards,
            Bill Combs
            ttursine@ earthlink.net
            http://home.earthlink.net/~ttursine
            '75 Superior 28', "Old Blue"
            --
            Politician's Credo:
            If you try and don't succeed, cheat.
            Repeat until caught. Then lie.
          • bobalou1@prodigy.net
            How much junk will it take to put a RV/TRUCK chassis over weight? I don t know thats why I trust the Engineers at Dodge, Ford and GM. They have been in the
            Message 5 of 13 , Oct 1, 2001
              How much junk will it take to put a RV/TRUCK chassis over
              weight? I don't know thats why I trust the Engineers at Dodge, Ford
              and GM. They have been in the business for about 100 years and make
              the big bucks. So who are we to change what took years of engineering
              to perfect?

              MY SUGGESTION: KEEP IT STOCK OR BUY A BIGGER RIG!!!

              Bob.
            • Bill Combs
              ... Some of us are just engineers who like to learn about the things they do. It s a sickness. -- Regards, Bill Combs
              Message 6 of 13 , Oct 1, 2001
                > on 10/1/01 8:53 PM, bobalou1@...1@... wrote:

                > So who are we to change what took years of engineering
                > to perfect?

                Some of us are just engineers who like to learn about the things they do.
                It's a sickness.
                --
                Regards,
                Bill Combs <ttursine@...>
                http://home.earthlink.net/~ttursine
                ---
                "The biggest cause of trouble in the world today
                is that the stupid people are so sure about things
                and the intelligent folks are so full of doubts."
                - Bertrand Russell
              • n7bqv@yahoo.com
                ... inflation is ... I would like to know if this is fact or opinion because obviously the safety of my family is at stake. My 1978 Dodge MB300 has singles on
                Message 7 of 13 , Oct 5, 2001
                  --- In classicrv@y..., Bill Combs <ttursine@e...> wrote:
                  > > on 9/30/01 12:09 PM, jwelles@a...@... wrote:

                  >Over inflation can be OK -- i.e., is safe if not good -- but under
                  inflation is
                  > *never* OK.
                  >

                  I would like to know if this is fact or opinion because obviously the
                  safety of my family is at stake. My 1978 Dodge MB300 has singles on
                  the rear, 8.75x16.5 D which are marked 2350lbs load at 65psi, but the
                  motorhome sticker says to run 90psi. I'm scared to do that, but it
                  handles poorly with only 65. Is it safe to put 90 in these tires?
                  Fearful
                • Bill Combs
                  ... No. That statement was bad wording on my part. I should have said: inflating to more than the proper level -- the level which the tables specify for the
                  Message 8 of 13 , Oct 5, 2001
                    > on 10/5/01 8:08 AM, n7bqv@...7bqv@... wrote:

                    > --- In classicrv@y..., Bill Combs <ttursine@e...> wrote:
                    >>> on 9/30/01 12:09 PM, jwelles@a...@... wrote:
                    >
                    >> Over inflation can be OK -- i.e., is safe if not good -- but under
                    > inflation is
                    >> *never* OK.
                    >>
                    >
                    > I would like to know if this is fact or opinion because obviously the
                    > safety of my family is at stake. My 1978 Dodge MB300 has singles on
                    > the rear, 8.75x16.5 D which are marked 2350lbs load at 65psi, but the
                    > motorhome sticker says to run 90psi. I'm scared to do that, but it
                    > handles poorly with only 65. Is it safe to put 90 in these tires?
                    > Fearful

                    No. That statement was bad wording on my part. I should have said:
                    "inflating to more than the 'proper' level -- the level which the tables
                    specify for the load the wheel is carrying -- can be OK ... but don't go
                    higher than the max listed on the tire."

                    Not a good idea to exceed the maximum pressure for the tire size; instead go
                    to a higher "load range" or a different tire. In 8.75x16, a load range 'E'
                    tire (used to be?/is?) available which raises the max load/inflation to 2790
                    pounds at 75 psi.

                    When talking safety, the rating of the wheel itself also comes into play.
                    Practically speaking, this is almost never an issue but should be checked if
                    upgrading the tires. The chassis manufacturer's repair manual should have
                    that data.
                    --
                    Regards,
                    Bill Combs <ttursine@...>
                    http://home.earthlink.net/~ttursine
                    ---
                    Talk is cheap because
                    supply exceeds demand
                  • Bill Combs
                    ... BTW, the tables I am using (from a 70 s issue of Trailer Life Repair and Maintenance Manual) don t show any 8.75x16 tires stouter than load range E. This
                    Message 9 of 13 , Oct 5, 2001
                      > on 10/5/01 8:08 AM, n7bqv@...7bqv@... wrote:

                      > --- In classicrv@y..., Bill Combs <ttursine@e...> wrote:
                      >>> on 9/30/01 12:09 PM, jwelles@a...@... wrote:
                      >
                      >> Over inflation can be OK -- i.e., is safe if not good -- but under
                      > inflation is
                      >> *never* OK.
                      >>
                      >
                      > I would like to know if this is fact or opinion because obviously the
                      > safety of my family is at stake. My 1978 Dodge MB300 has singles on
                      > the rear, 8.75x16.5 D which are marked 2350lbs load at 65psi, but the
                      > motorhome sticker says to run 90psi. I'm scared to do that, but it
                      > handles poorly with only 65. Is it safe to put 90 in these tires?
                      > Fearful

                      BTW, the tables I am using (from a 70's issue of Trailer Life Repair and
                      Maintenance Manual) don't show any 8.75x16 tires stouter than load range E.
                      This implies that none were made, at least up to that time.
                      ---
                      Regards,
                      Bill Combs <ttursine@...>
                      http://home.earthlink.net/~ttursine
                      ---
                      Helicopters can't fly; they're just
                      so ugly the earth repels them.
                    • mike_w@prodigy.net
                      I would never exceed the maxim PSI printed on the sidewall of the tire. Doing this is dangerous and will void the warranty of the tire. If you have handling
                      Message 10 of 13 , Oct 5, 2001
                        I would never exceed the maxim PSI printed on the sidewall of the tire.
                        Doing this is dangerous and will void the warranty of the tire. If you have
                        handling issues I'd look to the front end alignment and/or front end wear
                        items...ie ball joints, tie rods etc...

                        Mike W.
                        Latrobe, Pa




                        n7bqv@yahoo.c
                        om To: classicrv@yahoogroups.com
                        cc:
                        10/05/01 Subject: [classicrv] Re: tire pressure
                        09:08 AM
                        Please
                        respond to
                        classicrv







                        I would like to know if this is fact or opinion because obviously the
                        safety of my family is at stake. My 1978 Dodge MB300 has singles on
                        the rear, 8.75x16.5 D which are marked 2350lbs load at 65psi, but the
                        motorhome sticker says to run 90psi. I'm scared to do that, but it
                        handles poorly with only 65. Is it safe to put 90 in these tires?
                        Fearful


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                        [Non-text portions of this message have been removed]
                      • n7bqv@yahoo.com
                        Thank you for the clarification. Oh, I was wrong about 90 psi on the sticker. I re-examined it, now I read 75psi (funny how the mind works) Looks like the
                        Message 11 of 13 , Oct 6, 2001
                          Thank you for the clarification.
                          Oh, I was wrong about 90 psi on the sticker. I re-examined it, now I
                          read 75psi (funny how the mind works) Looks like the previous owner
                          stuck load range 'D' tires in place of what should be 'E' and I'm
                          finding out that 8.75x16.5E is hard to find, and expensive. Michlin is
                          about the only manufacturer of a 'E' range tire that size.

                          Has anyone replaced their Dodge 6x16.5 inch wheels with the modern 16
                          inch? What are the pros and cons, and rim width, tire size etc.
                          Thanks in advance a bunch.
                          Dave.
                          1976/8 Dodge MB300 316ci Jamboree class C 19 footer.
                        • tlman48
                          I also ran across this info. in looking up age and safety of tires. I did not know that light truck (? R.V.) tire pressure max. that is listed on the tire is
                          Message 12 of 13 , Dec 28, 2005
                            I also ran across this info. in looking up age and safety of tires. I
                            did not know that light truck (? R.V.) tire pressure max. that is
                            listed on the tire is not the same reading to be used like car tire
                            pressure. I will just quote so you can understand what I'm trying to
                            say!
                            It is important to note that the inflation pressure molded on the
                            side wall of a passenger-car tire is the maximim air pressure for
                            that tire. That is not the case, however for light-truck tires.

                            The inflation pressure molded into the sidewall of light-truck tire
                            is the minimum (that's right, the minimum) air pressure required for
                            that tire to carry the maximum weight molded into the sidewall of
                            that tire. Using less air pressure means the light-truck tire must
                            carry a lighter load.

                            While the tire-load rating molded into the sidewall of a light-truck
                            tire should not be exceeded, it is generally recommended that the
                            tire be inflated to the minimum pressure required to carry the load
                            plus an additional 5 - 10 psi. The extra pressure will help the tire
                            run cooler. It also acts as a reserve to offset normal loss of air
                            pressure. But the extra pressure will not add to the tire's load
                            carrying capability. Just keep in mind that the maximum air pressure
                            for a light-truck tire is the minimum air pressure molded into the
                            side of the tire plus 10 psi.

                            Do you all agree with this??
                            Hope it helps, Tim
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