Hello,
My wife has a Trek 2200 WSD road bike. I bought her a computer and cannot calibrate the rim size to get a proper reading from the computer. When I look on the Bontrager rims they have strange numbers. Could someone help me figure this out?....
The rim says, 700C 622 x14, 650C 571 x14. I cannot figure out if this means it is 700c or 650c.
This really wasn't much of a problem until tonight she had a flat. Now we need to purchase a new tube and the tube that was in the tire is from Performance, it has writing on the tube that says 20-571 SuperThin. It doesn't say anything about 700c or 650c or the other numbers that are on the rim other than the 571.
The tire itself doesn't say anything except for inflate to 120psi.

I looked at my tires, I also have a Trek. My tires make sense they say 700c x23. When I look on Performance or any other site I can find tires and tubes that will fit these rims/tires. I tried putting one of my extra tubes on her rim and it is too big. Can someone tell me what this 700 or the 650 means? I thought it might have something to do with the diameter of the tire and it's measured in mm, is this correct? Any help would be great. I need to get new tubes for her bike so we can get back on the road.

According to Trek, if her bike is a 51cm or smaller frame it has 650c tires. If it is 54cm or larger it has 700c tires.

It sounds like they use one lable for both 700 and 650 rims. Look at her (and your) tire - it will have a number like 23-622 if it is a 700c (622 is the tire bead diameter - 23 is the tire diameter) and 23-571 if it is a 650c. This is the ETRTO designation, now adopted by ISO. These numbers may be embossed in the sidewall rubber rather than as part of the label, but they WILL be there. This is your key to knowing what size tire to use. You can generally use a smaller tube in a larger tire, as the tube will stretch easily as it inflates. Using a larger tube in a smaller tire gets problematic as you can easily end up with wrinkles in the tube that can cause flats. Also, using a 650 tube in a 700 tire can make it a little more challenging to insure that you don't pinch the tube under the tire bead when mounting the tire. Tube WIDTH is usually not an issue - most people use a single size tube for "normal" road tires in the 20-32 mm range. If you have large 700c tires (35mm and up) then larger width tubes make sense.

If you want to really understand tire sizing, go to Sheldon Brown's site: http://www.sheldonbrown.com/tire-sizing.html

If you need the total diameter for your computer, just use the rim diameter + (2*tire height). If it's a 23mm tire, then for a 700c, it's 622 +(2*23)=668, for 650c it's 571 + (2*23) = 617

Any computer I'm aware of needs a metric circumference calibration. My wife's WSD with 650 X 23 tires is calibrated at 1930mm circumference. She weighs 105 and the wheel sensor is on the rear wheel, the rear tire usually has 110psi pressure. If your wife's computer sensor is on the front wheel you could try something slightly larger, maybe 1935. Or if it calibrates in cm instead of mm try 193 or 194. If you want her mileage and speed to match yours you can play around with the calibration on one or the other computer until you get consistent results.
The wife and I rode a 55 mile ride last Saturday, our mileage varied by 0.01 miles.

~Al