Computer Wheel Factor - DOH!
Posted On Friday, May 2, 2008 at at 7:49 PM by MTB Man
I'm actually doing a little better on my average speed on rides than I thought because when I took my dB4LW-C computer off my Ross MTB and installed it on my Raleigh road bike, I forgot to change the wheel factor from the 26x2.125 tires on the Ross to the 27x1.125 tires on the Raleigh. The manual for the computer has a chart that you use to enter a wheel factor to account for different wheel and tire sizes when measuring mileage and speed. The wheel factor is the circumference of the wheel in millimeters with the tire mounted and inflated to max pressure. So, the computer was reading lower mileages and slower speeds than what I was actually doing on the Raleigh. DOH! Better than the other way 'round, though, i.e. me finding out that I'm doing worse than I thought! ;-)
I have a DB4L and was wondering where to place the magnet on the spoke. The manual says a max of 60cm from computer. It seems to me that computer readings will change if the magnet and pickup are moved up or down the spoke. I have set the wheel factor.
Thanks,
-Bob
Bob,
I don't think it does matter where you place the magnet on the spoke. I think it computes speed and distance based on revs/sec x the wheel factor. So rev/sec will be the same no matter where you place the magnet. The main thing is that the TRANSMITTER is no more than 60cm from the computer. I put my magnet about 4 inches from the rim and it works fine. Of course the sensor/transmitter has got to line it's arrow up with the magnet. Hope this helps.
Thanks mtb man,
Some how I got it in my head that it would spin faster near the hub. I didn't think it through that revolutions are the same relative to the fork.
Thanks for the insight.
-Bob