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road bike wheel size on my computer?(5 posts)

road bike wheel size on my computer?jimsawino
Sep 12, 2002 5:54 AM
i just put an old nashbar computer on my road bike that had been on my mountain bike for the last four years. it always read fast on the mountain bike, and i'm not sure if it's set for a road bike or not. when i put a new battery in the wheel size read "2124". i have the standard 700c road wheels with continental gp 3000 tires. please help me, i just want to know how fast and how far i'm riding.
it's the circumference in millimeters...cory
Sep 12, 2002 7:11 AM
2124 is the circumference in millimeters of the tire it's set for. That's 83.6 inches (25.4mm per inch), which works out (pi = 3.1416) to a diameter of 26.6 inches. You can set it accurately by sitting on the bike (to compress the tires the way they are when you're riding), then having somebody mark a spot on the tire, then roll it forward exactly one revolution and measure the distance you cover. Then you figure out how to reset the computer to that number--different ones are set in slightly different ways, so good luck.
If it was always fast on the mountain bike (which has smaller tires), it may be set for a roadie, and might be close enough that you can live with it. Find some mile markers alongside the road and check it out.
The 2124 is a 212.4cm circumference...Quack
Sep 12, 2002 7:23 AM
To find the circumference of your tire, inflate it and measure how tall it is(in centimeters), multiply the figure by 31.4, and set your computer as close as possible to that figure.

Larry
got it set up. thanks for the help.jimsawino
Sep 12, 2002 9:50 AM
easy way to find circumference:Alexx
Sep 15, 2002 7:52 AM
First: find the diameter. this is easy. rim diameter + 2*profile. if you are using, say, 700x23 tires, it is the rim diameter (622mm) + 2*25mm = 672mm.
Next: Circumference = Pi * diameter. in this case, it equals 2111.15mm, or 2.11m.
see how simple it is?