Odometer - how accurate are they?

Inastate

Ello,

I recently bought a cateye micro cycle computer and it has an odometer to tell you the distance travelled.

When setting up it asked me for the wheel size, but I've just realised that depending on where the magnetic sensor is located on the spoke, from one end to the other, the odometer could give a vastly inaccurate reading of what the distance travelled is.

Is this correct and is it much of a problem? Have other people came against this, and if so, how did you deal with it?

Thanks a lot.

supersonic

The sensor counts revolutions - so the location makes no difference.

Deputy Dawg

It doesn't matter where on the fork / spoke the sensor is located as 1 rotation will travel the same distance at the tyre regardless.

The only place for inaccuracy comes from different tyre profiles effectively changing the size of the wheel.

vanamees

Odometers are very accurate if yuo set very accurate wheel size

Inastate

Aha! Thanks everyone. x

tenfoot

Just for comparison - the distance travelled on my Cateye computer always reads very close to my endomondo app installed on my phone.

Tank-slapper

Depends what you mean by 'accurate'.

If you want your computer to be accurate to within 100m over a 20km ride, then the wheel measurement you enter must be accurate to within 1cm.

Anonymous

Accurate enough for any real use, hell yes. Accurate enough for scientific experimentation to a quantum scale, er... no.

vanamees

26" mtb wheel 1 revolution is ca 2,1 m, 1 km= ca 500 revolutions. 2 cm inaccurate wheel size = 10m per km.

Anonymous

Cough (age old argument again) accuracy of single GPS measurement is +/- 32 feet (IIRC)

cooldad

Yawn

Anonymous

quite