Originally Posted by
Buglady
I replaced the battery on my little computer this morning, forgetting that this would erase not only the odometer reading (which wasn't that much, I only ran the thing for a week before the battery died!) but also the code that tells it what the wheel size is. So it defaulted back to 700 X 25C. I am running 26" wheels with 1-1/2" tires. How far off will my reading be, and is there a conversion factor I can use to find out how far I really rode today?
It's this computer:
http://www.filzer.com/products.php?id=4
User's manual:
http://www.filzer.com/img/products/4-instructions1.pdf
I think the correct wheel factor is 2030... does that sound right?
I am running metric, by the way, except for tire size.
Thanks!
1985 would be a more realistic default value for 26" 1.5" tires.
But the best way to be sure is to do a "rollout" test. Take your bike out on your driveway or the street, and position the front valve stem at 6 o'clock (straight down). Have an assistant mark the position of the valve stem on the pavement with a pencil or chalk.
Now, while pressing down on your bars to simulate riding weight, roll the bike forward in a straight line. Ideally, you'll be able to roll through 3 or 4 revolutions. Mark the ending 6 o'clock valve stem position.
Measure the distance between the two marks (in mm), and divide by the number of revolutions. This will be the circumference of your tire.