Speedos in modern cars are a bit how’s-your-father. Let’s not be coy about it: they lie. They read higher than the vehicle’s true speed.
Drivers striving for a meaningful, bragworthy result from a pass down the main street of their local town after an afternoon watching the drifting are led astray by the stock speedometer. Before they know where they’re at, they’re blowing a load through the dump valve and claiming top speeds which just aren’t true.
The answer is a high-accuracy unit like this one from Supercheap Auto.
It’s a special-order item, but for a $1004 the Autometer Ultra Lite is accurate, has incandescent lighting around the perimeter of the dial, two trip meters which will measure up to a million kilometres, is compatible with two-wire and three-wire hall effect speed sensors, and comes complete with a bulb-and-socket assembly with a couple of different bulb covers.
Or you could run a $130 GPS from Amazon. Or wait for the mobile speed-camera fine to arrive. Those bastards seem to be fairly accurate, eh?