have an 08 gt shelby with new gears. stock size tire and wheel. when i open up the speedo tab i can change the final drive ratio. ok that was easy. but the speedo doesn't change much or at all.

there are a couple things i am not sure about.

1; "use vid" enable/disable. should i select disable?

2; "n/v base" do i use algebra to figure out the new value? or do i leave it alone? or?