Prplprowlr,
The manual for the Predator Programmer can be downloaded here:
http://www.granatellimotorsports.com/pdf/manual27.pdf
Look for the "Actual Wheel Size" setting.
According to the math, changing from 35" to 37" tires will result in the speedometer showing your speed 5% slower than you are actually running. When the speedometer shows 80, you would actually be running 84.
Klaus
Rare 2003 H2 with UM8 Integrated Navigation Radio
Skull & Bones Member since 2003