Garmin/Cateye tyre size, distance discrepancy

The wife and I went out for a ride recently and got very different distance results.
My wife has a Cateye wireless computer I have a Garmin Edge 510 and we also used Strava on a mobile phone. Now I realise there is always going to be some discrepancy between different recording devices but I wondered if the tyre size entered in each device is correct.
We are both riding on 700x25c tyres but the Cateye paperwork says set tyre size to 2105mm and I have always had my Garmin set to auto which sets a size of 2114mm. I realise Strava does not have this calibration function (as far as I am aware)
On our ride My wifes Cateye recorded a distance of 13.8 miles, her phone running Strava recorded 17.9 miles and my Garmin recorded 14.8 miles.
What size do you set your device to?

Rickshaw Phil

Overconfidentii Vulgaris
For accuracy I'd suggest measuring the actual rolling circumference of the wheels and entering that. The figures given in instruction leaflets are only a guide and aren't often accurate.

Having said that, you are looking at over a 20% margin of error between the Cateye device and Strava - something is really not right there.:scratch:


Fuelled with Jelly Babies
South Wales
Measure a ride on map my ride or whatever.

Ride it and make a note of your distance from the cycle computer.

Work out the percentage difference between the real distance and recorded distance.

Apply this percentage to the inputted wheel circumference .

Try the ride again , this time it should be close to accurate.
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