setting up speedo for flat bar racer

eurotrotter

hey guys

im just looking to configure a speedometer for my flat bar racer
im just wondering what wheel dimensions to put in, its the part of teh setup where '205' is flashing, if that means anything to anyone!
one other thing as well, im new to dublin and im hoping to join a cycling training group of some sort, I was wondering if boards have any cycles planned over the next cpl of days/weeks?
thanks very much,
ed

kenmc

you need the outer circumference of the wheel and tyre, in mm usually. So it will depend on your tyre - I'm guessing it's 700xSomething, eg 23/25/28
sheldon, as usual, knows best

kuro_man

Pump up tyres. Stand bike upright on a flat area with valve at 6 o'clock and mark the ground beside valve with chawk. Roll bike forward until valve returns to 6 o'clock, i.e. one full wheel rotation and mark the ground at the new location. Measure the distance between the chawk marks.

I did this with 700C wheel @ 80psi a few years ago and I think the circumference was 1883, but can' be sure (I should have written it down to enter it again when batteries die.) It was lower than most calculations/charts which produced a circumference of 2100 but I cycled 7 miles to Blackrock and then checked the distance with google maps and it matched.

If you over-estimate it, it will flatter your speed/distance.

Gavin

Also/Or, measure radius of wheel & tyre.
2*PI*R