speed is off

[kc_sheets]

i have a 04 chevy silverado 5.3 with a 4" suspension lift and a 3" body lift and i have 37 inch tires and 22" rims and my speed is off by like 5 at 40 and 70 its around 7 to 8 i change the tire size in the programer to 343 metric i looked up the conversion online and im wondering if theres any way to fix the speed so it will show correctly thank you

pic http://www.krissheets.com/22.JPG

[mikel]

Try telling the Predator that the tires are shorter than the numbers on the sidewall.
Most #'s on the sidewall come out to be taller than the tire actually is, yours are likely closer to 35.5-36" tall, rather than 37.

Thanks