For those trying to figure out how accurate your speedometer is,
the easiest way is to beg or borrow a handheld GPS receiver (consult
your favorite boater or backpacker). Most GPS receivers will read
out speed so all you need is a steady driver and a nice straight
stretch of highway (Kansas or West Texas come to mind). My '85
with 185R14 tires is within +/- half a mile per hour at 60.
Frank
85 GL
San Antonio Texas