Re: Quick question about entering tire size for cycle computer
|Much more acurate way is multiply the diameter of the bike in mm (700) by pi (~3.1416)
Depending on the tension of the spokes, brand of tire, the air pressure in the tire, and the weight of the bike and rider, the actual diameter will vary from the nominal 700 mm. Using the roll out method, one revolution on my bike is 2190 mm, which would make the effective diameter 697 mm, even though it is labeled as 700 mm. According to Specialized, the recommended setting for that tire is 2192.
The bottom line is if you want to be accurate, you need to measure. On the other hand, the difference between 2190 and 2192 mm per revolution of the wheel is about 57.8 inches per mile or 0.09128%. I can live with that. On a measured track, that would be less than the difference between riding the inside of the lane versus the outside of the lane.