Originally Posted by
Fat Boy
Agreed, which is why I mentioned it in the spirit of full disclosure. I just used Sheldon Brown's numbers to get a quick and dirty start. I just Google Earth'd my path. It shows that I was about 1% positive on distance, so that means that my was about 0.2mph slower than my computer showed. When I get my Garmin, I can get more scientific.
Bike computers are very accurate for speed & distance when you calibrate them. Why not measure the roll out for each bike and enter that value into your bike computer? Then you'll be able to compare the results directly. Shouldn't take more than 15mins for both bikes.