My first computer was a Push - there were settings for about 3 different wheel sizes I think. Circa 1984... toe clips, exposed cables, and DT friction shifters, and freewheels.


When electronics got better, you could input your tire circumference to the mm... and there were all kinds of arguments about how to get the perfect measurement considering tire size, air pressure, rider weight, etc... everyone wanted the highest accuracy possible, and it was a PITA.

Then when GPS came along, most people said "yeah, +/- 10% is fine".

I have both a Garmin watch and cyclocomputer... I pick whichever one reads higher to post on Strava.