There is a how-to on shotimes.com for calibrating the speedometer on a Taurus SHO. It is entirely absurd. Here's an overview:
With the speedometer somewhat apart, you hold a left and right pin with strings and pull up or down to adjust the needle position so that it matches the speed. To get the speed, the how-to recommends you take a passenger and have them time you between mile markers until you reach a steady 60 mph. Once that's achieved, you begin wrangling with the delicate workings of the speedometer (while presumably holding the wheel with your knee as you peer into the dash).
This would be a tough job even if they included Alan Shepherd, Jim Lovell, and Ken Mattingly.
With the speedometer somewhat apart, you hold a left and right pin with strings and pull up or down to adjust the needle position so that it matches the speed. To get the speed, the how-to recommends you take a passenger and have them time you between mile markers until you reach a steady 60 mph. Once that's achieved, you begin wrangling with the delicate workings of the speedometer (while presumably holding the wheel with your knee as you peer into the dash).
This would be a tough job even if they included Alan Shepherd, Jim Lovell, and Ken Mattingly.