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    Actual tire diameter

    For the tire diameter setting, do you enter stated diameter or actual diameter? My full suspension 26" tires measure 27.2 tall, vs my fat bike surly nate 26" which measure 29" tall.

    #2
    I think it is stated diameter...not actual diameter but if you have a fat tire, then you probably should go to the next size up.

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      #3
      Tire diameter is measured for the rim size.

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        #4
        I'm getting different mileage readings between the fat bike and full suspension doing the same ride, both with 26" rims.

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          #5
          Sheldon Browns gear calculator specifies fat tires at 10 psi. I suspect that to be the most accurate you should have someone accurately measure the loaded radius while you are sitting on your bike and double that figure.

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            #6
            The Bafang wants you to specify the rim diameter. But, fat tires are bigger, as you noted. I use the 29" rim size, and get real close for my 26x4.8 rear tire at 8-10 psi. Rim width make a difference, as well as pressure.

            Best way to measure the OD of the tire is to put the stem at the ground, weight the bike by getting on it, at your riding pressure, and measure how far the bike goes until the stem is at the bottom again. One revolution. Divide by Pi, that's your actual effective rolling diameter.

            With the Bafang controllers there's not much point in getting that accurate, but for a bike computer that accepts wheel diameter or circumference in mm, it's worth it.
            Last edited by JPLabs; 01-12-2017, 07:54 PM.
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              #7
              29" is close enough for me. I'm using a 26x3.8 @ 8psi. Rim width is 80mm.
              thanks

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