I just started using Strava about three weeks ago, and I enjoy it. But one of the things I've noticed is that the maximum speeds Strava gives are different than the speeds my cheap bike computer gives. On today's ride, Strava had me at a top speed (downhill) of 36.7 mph. My bike computer had me at 31.7 mph. Both times were on the same stretch of road. When I installed my computer, I hand measured the wheel circumference, and the distances given by the two aren't that far apart (Strava said I rode 28.6 mi. today and the computer said 28.5 -- no big deal). But the max speed thing baffles me. Any ideas?