Tire size basics

[wildman]

I am in desperate need to replace the rear meats on my SPD Tricub. The originals are one-piece balloons with no size imprinted. I have inflated these to recommended circumference and measure OD at 18½” and width at 10¾-11”. I am trying to size a tire/wheel to match these dimensions as close as possible. I’m looking at various tires 18x10-8 to 20x11-8 (rim diameter is immaterial at this point). I have also physically measured several ATV-type tires and get various results compared to the imprinted size… i.e. 22x8-10 = actual 20¼” x 9”and 24x11-10 = actual 22½” x 12”.

It there a way to predict actual physical dimensions based on the specified size? I know that the rim width can affect the size to some degree. I'm trying to avoid ordering something and be too far off on the size. Any advice appreciated.

[jpswift1]

I believe that each tire and manufacturer will differ in actual size. If you can find them, I'd say get a pair of Nankang Chevrons, 21x12x8. The tread pattern is not very aggressive and the tires are very soft and squishy......much like a balloon tire.

[wildman]

Thanks for the info jp. This photo shows original balloon (left) vs Carlisle 22x11-8 (right). These are the tires that viking1 is going to put on his Wedge. I borrowed a pair to see how they would look on the Tricub. The Carlisle measures about 1" wider and 1" taller than my balloons.
DSC05154.jpg
If I could get the Nankang 21s they should be fairly close. Do you know any sources?

I am not totally bent on replacing with chevrons. It would be nice to match the original look, but at this point I'm more interested in tires that hold air rather than match the look. I still hope to find some "display" tires that hold air and "look" original, then have a pair of everyday tires.

[thebuggyman1]

FYI in an ideal world the math is: circumference divided by pi (no greek letters on my keyboard) (3.1416). A typical baloon tire (common size) is 62" so 62/3.1416= 19.735 or a 20" tire

[wildman]

I must have some oddball balloons. I've seen most balloons are either around 62" or 65". Mine say on the sidewall, "Inflate to 58". The owner's manual says to inflate to 61". I inflated to between 59-60" and measured the 18½". In a perfect world, I would know the exact tire size I need. The imperfect world is what we are left to deal with.