thirdcrank wrote:Unless something is obviously way out, I'd say it's not worth bothering about, on the world-wide scale.
I must have posted before that I bought a Cateye (Mity 2?) and decided to check it on a measured mile. To give a bit of local detail, I chose the one in Baildon, just along the road from where Ellis Briggs shop used to be. I manually set it to what it said in the manual for my wheel size, then road backwards and forwards (always going forwards of course) along the measured mile, fine tuning the computer at the end of each mile ridden. After doing that for some time, I checked the setting and I was back to the setting recommended in the handbook. I suspect one of the things that this shows is that the slight deviations from a straight line when riding, especially in busy traffic, have more effect than a minute difference in wheel circumference.
There are better ways of getting the miles in.
A MITY 2 I'm on the Mity3, its well battered and glued and soldered in place but still working.
Annoyingly the setting of the wheel size on the mity3 leads to inaccuracy, calibration is to whole centimetres and wheel circumference is 2136 mm - that could knock my yearly total out by 15 mile (and 15 mile is 15 mile especially into the wind)
I do calibrate all mileometers with bike-hike http://www.bikehike.co.uk/mapview.php
, very important to do so with vehicles if you are interested in true mpg figures. cars and vans are notorious in over-reading distance, (my van is 4.5% out and the car 1.3% out). In comparison my bike is pretty near spot on 99.7% accurate.
However when it comes to my weekly average of 150 mile, this is done purely through bike-hike and no ride can be less than 10 mile. So little rides to the shops don't count
take the SUV instead.