If you are talking about this, and you have it installed correctly,
http://www.cometkartsales.com/store/gauges/images/mychron/aim-speedcable.jpg
you need to enter to tire circumference and pulses per wheel rev into the gauge. You can do this thru Race Studio or in the setup screen on the Mychron 3 .
Here’s a link to the Mychron 3 plus/gold manual
http://www.aimsports.com/pdf/manuals/My3_PGA_eng_110.pdf
Pages 33 and 34 show how to setup speed sensor on the gauge.
