Originally Posted by
JLauren
Today I rode with both computers. For the most part the speeds were identical, occasionally + or - 1 kph. What I found interesting was that the distance was off by .50 km: 30.36km from the front/Sigma and 29.86km from the rear/Astrale.
You have what is know as; "The Two Watch Problem". It goes; "The man with one watch knows what time it is. The man with two watches is never sure."
I have Cat-Eye Enduros on two road bikes and also have a Garmin Forerunner 305 GPS running/bicycling watch. I'm amazed on how closely the Garmin and the Cat-Eyes agree as they read within 0.1 mile of each other on 35 mile rides. However, I do set my Cat Eyes slightly lower than the recommended calibration number. For a 700x23 tire they recommend a calibration number of 210 and I use 209.