Help with my tire pressure - newbie

Discussion in 'Tires / Brakes / Bearings / Axles' started by Woodfaerie, Jun 23, 2019.

  1. Woodfaerie

    Woodfaerie New Member

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    Trying to keep my cool but sheesh am I frustrated. I will have my maiden voyage with my 87 Startcraft later this week. I headed on out to the air pump at a local gas station that provided LOTS of room for me to maneuver with the intentions of making sure my tires were inflated properly. I have Hi-Run 5.70-8 tires that says I have a max of 100 psi. Yikes!! That seems like an outrageous number. But in all the online researching I find that I should keep it at the max. Well, I can't get either tire inflated over 70. I even went to a different gas station thinking my pump hose was not working as it should.
    I don't have any mechanical mind to help me out, I am a solo camper. What on earth am I missing?? And how on earth do I get 30 lbs of air in? It would take forever!
    Do I need to buy a compressor???? oh boy.....I am thinking I can't go to gas stations...
    UPDATE cripes I feel dumb. okay so I learned that the typical gas station pumps are rated for 65-70 max so I can't inflate them there. (probably why I never saw any pups at one) Do RV dealers offer that service?
     
    Last edited: Jun 23, 2019
  2. generok

    generok Well-Known Member

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    Well, if the sidewall says 100 psi, that's the max, but that seems VERY high to me. Typically those 5.70-8 tires run around 50 psi. Check the sidewall again and see if you can't find a max inflation pressure. Heck, I've got Load Range E tires on my trailer and they run at 80psi, so 100 psi sounds high to me.
     
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  3. Woodfaerie

    Woodfaerie New Member

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    Yep, most def says 100. I just checked.
     
  4. generok

    generok Well-Known Member

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    Son of a gun, it sure does.

    Ok, well, those pressures could be problematic at some gas station air pumps. I suggest you go to a TRUCK STOP. They will have air and a nozzle meant for trucks and 100 psi is no problem. You can (and probably should) buy yourself a little 12V air compressor and keep it with you when you tow. This little Viair units connect to your TV or PUP battery and can inflate to 100 psi (it will take some time).

    https://www.amazon.com/Viair-00088-...89&s=gateway&sprefix=12V+air,tools,234&sr=8-4

    Best of luck!
     
  5. tombiasi

    tombiasi Well-Known Member

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    Most stations don't have 100psi at the pump Go to a truck station.
     
  6. tombiasi

    tombiasi Well-Known Member

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    Load range D 5.70 x 8 are typically 100 PSI
     
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  7. Anthony Hitchings

    Anthony Hitchings Active Member

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    a quality bicycle pump works well, the kind with a footplate, I paid around $35. Fits both valve types (Presto and Schrader). BTW - quicker and more reliable than just about any 12V compressor of the compact kind. I also have a Smittybilt compressor - it works, but I am NOT impressed with it.
     
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  8. Woodfaerie

    Woodfaerie New Member

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    thank you so much for your help! Would this unit be appropriate? https://www.amazon.com/dp/B01N33MPKO/ref=emc_b_5_t
     
  9. generok

    generok Well-Known Member

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    Woodfaerie likes this.
  10. gec66

    gec66 Member

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    Keep in mind the proper method is to inflate the tires "cold". That means before they have traveled down the road at all. My tires are to be set at 80 and on a long trip I had to drive about a mile to a gas station to check them and they were already at 85 by that time. If you ever do check them after they have been moving and find they are above the max pressure, DO NOT adjust them back down at that point. If you do you are effectively lowering their "cold" pressure and thus lowering their load capacity. In fact you would be safe going 5 lbs above the max pressure on a "warm" tire. Trailer tires are rated for capacity at their max pressure and RV builders are famous for using components, including axles and tires, that have little if any spare capacity. Tires are engineered to handle normal pressure increases from going down the road and are only susceptible to blow out due to excess pressure from heat when another component such as a wheel bearing or stuck brake heat them up beyond what rolling resistance adds.

    P.S. Sitting in the sun can also cause a "warm" tire scenario vs in the shade and it's not uncommon for one side to register a few pounds higher for the tire the sun shines on vs the tire that is in the shade.
     
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  11. Woodfaerie

    Woodfaerie New Member

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    thank you! I have both kind of bike pumps.
     
  12. Minimalist

    Minimalist Member

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    A bike pump is what I am typically using but only to top the tires off. Not more than 20 PSI. I also might be spoiled as a cyclist but for $35 you'll get an entry level pump.
     
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  13. Woodfaerie

    Woodfaerie New Member

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    Thank you, so much great information.
     
  14. bheff

    bheff Active Member

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    My lezyne floor pump semi agrees with you.
     
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  15. Arlyn Aronson

    Arlyn Aronson Well-Known Member

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    We keep less than max in all our trailer tires since that pressure is for max payload. We'll only go to the max rating if whatever we're hauling is heavy. If you are at the rated tire PSI and don't have that much weight in your trailer, its ride sure is harsh.
     
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  16. Grandpa Don

    Grandpa Don Active Member

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    At 100lbs., I just hope your tires are not 1987 vintage...
     
  17. Matt Benoit

    Matt Benoit Well-Known Member

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    My tires list 105psi cold on the sidewall. I stick to 100.
     
  18. tombiasi

    tombiasi Well-Known Member

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    Why?
     
  19. Matt Benoit

    Matt Benoit Well-Known Member

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    My pump can't go any higher.
     
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  20. Matt Benoit

    Matt Benoit Well-Known Member

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    My tires are also 2 load sizes higher rated than I need so.. I'm not worried about the 5psi
     

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