speedo calibration

[2whlin]

I own a 2001 21i and took it out for the first time this season last weekend and noticed one of the speedo gauges was off by 10 mph. When we put it up last season it was never that far off. How do you go about calbrating them? I know there are two knobs on the panel that are supposed to do this but don't have a manual and not sure how it's done.

Thanks for your time

[TeamAllen]

I'm not sure of your exact setup, but you will need a GPS to compare the speed and make the adjustment.

[2whlin]

yea, I was thinking of borrowing a buddies GPS.