i was wondering if any one knew how to calculate the size that should go into the speedometer i figured out how and where to hook it up but im not sure if you need to know this or not?

 

What kind of speedometer? Such as one that is designed for a mountain bike? I bought one like that, and I had to input the circumference, in inches, of the tire that had the speedometer pickup mounted to it.

 

I found a cloth tape measure at the hardware store that had inches on one side and metric on the other. I wrapped the tape around the middle of the tire and entered that in the spedo.

 

Just put a mark on your tire and a mark on the garage floor right underneath it. Then roll the quad one full tire rotation (until the mark is down near the floor again). Now make another mark on the floor directly below the tire mark. Then simply measure the distance between the marks on the floor. This will give you the exact circumference of the tire accounting for pressure, weight of the bike, etc. That's how I did mine and it is within .5 mph of the GPS. I mounted my sensor on the disc gaurd and held the magnet in place on the wheel with JB weld. For trial fitting and such, you may want to use duct tape to hold the magnet until you find the right spot. Hope this helps.