[newBDR]

You guys with the 17" wheels, do you think your speedo is accurate? Have you verified it? I have the M3 upgrade, 17" wheels, autometer reverse 180 speedo. Earlier car, #31. I think it registers on the high side. At an indicated 60mph I seem to be just flying past others on the highway. I've yet to drive a measured mile to verify. What's the simplest way to do measure it accurately? Does backdraft change the gearing for the speedo depending on which wheels, rear end you purchase?