How buoyant is a standard truck/van tire and rim inflated to just above the pressure required to seat the two?

I'm considering using a few to float one end of a temporary dock while the one I normally use is on dry land for a month or more of repairs.  Obviously it will vary depending on the size of tire and weight of rim...but generally speaking, how much more than neutrally buoyant is one?

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  • 3 weeks ago
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    As you’re aware, there are a lot of variables here. 

    But I worked for many years for a canal trust in the UK, and that involved a lot of recovery and dredging of dumped waste. I recovered many hundreds of fully inflated motor vehicle tyres mounted to rims, and don’t recall ever finding one which floated. The mass of the rubber tyre and of the rims were always greater than the buoyancy granted by the air in those tyres.

    Despite all that, you don’t need to accept what I’ve typed here. You’re clearly in a position to find out for yourself: Attach a complete car or van wheel with a mounted tyre to a suitable tether and throw it into the water. Then use the tether to pull it back up again. If what you’ve chosen does actually float, experiment with a few rocks to establish just how little excess buoyancy the wheel has.

    • Robsteriark
      Lv 7
      3 weeks agoReport

      Still going to be way too heavy, IMHO. But as I suggested it is very easy for YOU to confirm or not whether that will work. I never tested the pressure of the junk I recovered but none floated and very many were still inflated to some degree.

  • 3 weeks ago

    @ Old Man Dirt - is right; it's going to sink.

  • 3 weeks ago

    It doesn't matter how much air pressure is in the tire! The combination has to displace more water then it weights to float. Truck tires on a rim will not float in water. Ditch the tire and rim. Just use an inner tube. They cost less, weigh less so they can float more.

    • bob doug3 weeks agoReport

      Inner tube?  I haven't seen an inner tube for a truck tire in 20 years.

      And if air pressure doesn't matter, why do cans full of compressed air sink...but "empty" cans float?

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