TimD

Find someone who has a handheld GPS receiver. I have one for mountain biking - they only cost £100 and can pinpoint your location to within about 20 feet.

Autocar have one, and say that it is as accurate for top speed readings as their mega-bucks timing gear.

My scoob on standard 16" wheels with worn-out tyres would be doing 66mph at an indicated 70mph.

Tim

X SOOOBY

can any one tell me what how accurate the speedo is in my my00 with 215/40/17s fitted as it would be nice to know how fast or slow i`m going

Nathan L

It shouldn't be that much different but the only way to be sure is to take it to a rolling road as far as I know.

Nathan

Veracocha

I got an indicated 152mph in my S3, my mate in the passenger seat read about 146 with his GPS. The higher speed you go the less accurate the speedo becomes.

Neil Smalley

I used my friends GPS system to gauge my speedo accuracy.

Results can be found here

dteagles

Morpheous are developing a sat nav type of application go to on a PC/palmpilot and link to their Geodesy unit (the one that locates speed camera's via GPS).