I know all speedos are out generally, but on my 3 door Cossy i have 205 - 55 - 15 tyres on the rear just as i got em at a good price, but even at 20mph my speedo shows nil, then from 20 upwards it kinda lags behind a bit lol, i just wondered if it was as simple as the tyres, and yes im on standard 205 - 50 - 15 fronts, cheers.

 

Mine is 8mph out @ 170mph

Only doing 162 timed by Datron.

205/40/17 tyres

Steve.

 

i should say that its faulty then rather than out, just wondering if the tyre issue is a cause.

 

Nah m8, your tyre's wont be at fault for making your speedo that much out...wiv regards the non reading until your up to nearly 20mph, check speedo head chap and/or cable condition where it mates to the head and gearbox