Got to make sure i ask enough annoying newbie questions as possible ok i put on a bike computer and my speed seems like its right most of the time... but then sometimes it'll jump way off.. like it said i was doing 18 then jumped up to 40mph and then back to 18.. so i'm assuming its on there wrong. The instructions didn't really say where to put it on the spokes... does it matter as long as the magnet lines up with the sensor or what? any other ideas why the readings might be wrong, or maybe just sometimes they mess up? man i hate being new and ignorant, thanks for any help.