Originally Posted by Looigi

Of course there's a fair number of us here who did a lot of riding long before bike computers were available. One option from long ago was a counter with a cog on it that fastened to a fork leg and got tripped by a bolt like thing attached to a spoke. The bolt would engage the cog and increment the counter for each wheel rotation. You had to do the conversion from wheel rotations to distance in your head (or with a slide rule. no calculators back then). If you had a watch, you could then noodle out your speed.