| Author | Message | ||
     Froggy |
Anybody know the circumference of the rear wheel on a XB? I am running a standard run of the mill Scorpion Sync 180/55/zr17. It’s been too long since algebra class to figure it out, lol. | ||
| Badlionsfan |
diameter x 3.14 (known as pi) | ||
| Gentleman_jon |
I don't have the spec.s for the Pirelli, but the Dunlop Qualifier is supposed to be 1991 mm or 78.4". This is more or less of a proforma dimension, as the actual circumference depends on the wear of the tire, and the speed at which it is being ridden: many tires increase in diameter at higher speeds. Considering the accuracy of tachometers and speedometers, the number above should serve for most purposes, as there isn't much difference between tires, but there is some, of course. | ||
| Teeps |
Here you go, just plug in the numbers and the program does the rest. http://www.powerdog.com/tiresize.cgi | ||
| Badlionsfan |
that program works, just like dia X 3.14 does. program sez 77.9", i come up with 77.872" based on 24.8". more than one way to skin a cat! | ||
| Jos51700 |
Please note that the actual diameter, overall, is not 17". That's the diameter of the shoulder where the tire mounts up. | ||
| Froggy |
Cool thanks! I ended up plugging in 78" based on what John said, and it ended up being almost spot on, just a hair too high at high speeds. I will try 77.8 now  | ||
| Drfudd |
the calculated wheel diameter is 24.795... http://spreadsheets.google.com/pub?key=piMa420IFsf gb2gr2Irt5fg&gid=3 I calculated it on my spreadsheet , its actually pretty easy. Based it on 180 mm wide with a 55 ratio profile. | ||
| Azxb9r |
Put a mark on the tire, and a mark on the ground. Roll the bike forward till the wheel has done 1 complete revolution and mark that spot, then measure between the marks. Circumference changes a fair ammount with tire wear, so a new tire will be different than a worn tire. If you only need to be in the ballpark, diameter X 3.14 is fine. | ||
| Blake |
Even easier: A dab of white-out on the tire. Measure the distance between the two white marks on the pavement. | ||
| Punkid8888 |
All the calculations in the world won't get you as close to what AzxB9r, and Blake just said. Sometimes old school thinking is easier and bullet proof |
