Wheel size and bike computer

[BleeckerSt_Girl]

How timely. I noticed on Saturday that my bike computer is overstating my mileage and, by extension, my speed. I'm going to have to measure my wheels to get a more accurate reading. Grrrr.

If you feel your car odometer is accurate and you have a bit of patience, then you don't really have to actually measure your wheels.
Just drive a favorite regular bike route you do regularly, and mark what your car odometer reads for it. Then ride it on your bike. If the bike odometer reads higher than what the car said it was, then start resetting your tire circumference setting slightly lower by one or two digits at a time. Likewise, if your bike computer reading is lower than your car reading, adjust your computer setting for a slightly bigger wheel circumf. Make these adjustments a little at a time and then keep checking them whenever you do your regular ride. Re-ride and reset until your bike computer matches your car reading.

[MomOnBike]

We use the roll-out method, and accept that the figure is always going to be slightly off. DH's computer always seems to read faster/farther than mine does, but {shrug} maybe that just means he weaves alot.

An alternative to driving a route with your car is to use highway mile markers - if they are on a route you do. Again, one mile probably tell you much, but over 2-3 or so miles, you'll get an idea of the accuracy of your number.

[stacie]

try mapmyrun.com You can even calculate zigzagging across the street if you'd like. I've always just done as LisaSH says and trusted it was close enough. s

[li10up]

Now I know how to increase the speed and distance of my rides without all that pesky training! Just reset my wheel circumference!!!