Tough break.....
I had the dumb luck fortune of driving by one of those "Your speed is ___ " automated signs during my test drive. Learned right then and there that the speedo was off by 10mph (to the high side, so now I just subtract 10 from the speedo and know I'm in the safe zone. One of these days I'll crawl underneath and install the right speedo gear (probably after I change to 17's).