Thats what got me started. I had read that they are all off by 5 mph, but when my wife was running beside me(in the truck, before you ask), she said it was dead on at 60. Thanks for the answers. I now know how to run in the speed zones.Can't speak for all Harley's but mine is on the nuts up to 55 mph, after 55 it's off by 10 mph. Example... if it reads 75 mph I'm actually only going 65!