My experience with wrapping wheels and railings is that just doing the geometry give a good approximation. The line will stretch and get longer, but it gets flatter and skinnier at the same time, so a good first approximation.
1-inch tubing has a circumference of about 3.14 inches. It will take about 8 turns of 1/8-inch cord for each inch. A 30 inch wheel is 94 inches around, so 94 x 3.14 x 8 / 12 = ~ 200 feet.
I find the knot pattern irritating to the hands, so I have always (my last two boats had wheels, and I also wrapped certain slippery railings by stairs) just used a plain wrapping, since it is more comfortable for me. Looks are the least important factor.
I agree with @thinwater. I tried a couple of fancier braids but went with just a flat wrap of paracord. More comfortable on the hands and the added friction isn't needed.
