New Bike and old speedo

[Rickshaw Phil]

^^^ +1 for measuring. The figures in instruction sheets are only an approximation and may be quite different from what you actually have on the bike.

 

[youngoldbloke]

^^^Yes just changed tyres on one bike (Aksiums) from Gatorskins to Lithion 2s, and there was a considerable difference in the circumference. The circumference of Gatorskins on Shimano 501s was different to the same tyres on the Aksiums too. I measure the diameter as accurately as I can using a spirit level held against the top of the wheel (held vertical), and then multiply by 3.14159

 

[Grimgor]

Thanks, I'll go for the measurement way.

I was thinking about using the iPhone with an app, but I couldn't find a good looking holder, so the smart cycle computer is the option I'm going for.

 

[Cycleops]

Most cycle computer makers have a manual which can be downloaded in PDF format.