AussieSteve
Active Member
I've fitted a (Cateye) bike speedo/computer to my bike and originally set the wheel circumference to the figure in their chart for my tyre: 26" x 1.95" MTB - 205cm.
Today, I got around to checking the actual circumference, under load - 202cm.
(I set the bike with the valve at the bottom and marked the spot, then sat on the bike with my normal weight distribution, rolled forward one turn and measured the distance.)
I also have a cheap Chinese speedo on my electric bike and it was even worse - 208cm recommended, 200cm actual.
I only weigh 50kg, so most people would have a much greater error. Each brand of tyre would also be different. Pressure makes a fair difference too.
I've noticed some of the extraordinary speed and calculated RPM claims for these bikes and wonder if this has something to do with it?
... Steve
Today, I got around to checking the actual circumference, under load - 202cm.
(I set the bike with the valve at the bottom and marked the spot, then sat on the bike with my normal weight distribution, rolled forward one turn and measured the distance.)
I also have a cheap Chinese speedo on my electric bike and it was even worse - 208cm recommended, 200cm actual.
I only weigh 50kg, so most people would have a much greater error. Each brand of tyre would also be different. Pressure makes a fair difference too.
I've noticed some of the extraordinary speed and calculated RPM claims for these bikes and wonder if this has something to do with it?
... Steve