Bike computer V Gmaps pedometer

Jeffm587

How accurate are on board computers, does it depend on model etc or positioning of the pick up on the spoke perhaps? Sat morning I went - Drumcondra - Malahide - Baldoyle - over Howth (church side)- Coast road to Drumcondra. Bike computer said 48k and GMaps said 45k and I would lean towards gmaps being the more accurate but not sure.

Morrisseeee

I'm only a newbie myself to bike computers, I've got a wired model with cadence, its very reliable and very accurate, but............2 things: 1> make sure you have the right wheel size (if appropriate) entered into the computer settings, 2> try and have the 'sensor to magnet' partnership very close, ie. within 3mm.
ATM, I'm on the look out for a computer that logs the data, and one that you can upload it to your PC, but...............there doesn't seem to be that many options around.............bummer.

seamus

Your computer would definitely be far more accurate than google maps. Google maps will very often show a route as being shorter than it is - the roads don't curve as late as they do in real life and so google maps takes a "shortcut" and you lose that distance.

If you use iMapMyRide on the iPhone and look at the overlay on a Google map, the two only roughly sync up.

Gmaps are good for route finding and rough estimation, but they're nowhere near gospel. Openstreetmaps are much more accurate. 3km over 48km is only 6% off the actual distance, which sounds about right.

blorg

Bike computers are very simple things, they just count wheel rotations and multiply that by wheel circumference. There can be a certain amount of variance depending on things like inflation pressure but ultimately they are as accurate as the wheel size you enter into them. If you want absolute accuracy you need to do a "roll out" test sitting on the bike to measure your tyre's actual circumference but the manufacturer's conversion table is close enough for me.

Jeffm587

Thanks for the replies, the computer was already on the bike when I got it , but I am pretty confident they would have entered the correct wheel size. I will have a look later in the settings. The mag -sensor gap is deffo in the region of 3mm so I guess the computer would be the more accurate after all. I have the Imap my ride app also, just havent got round to using it yet. Next time out I will run it and see how it compares.