Wheel Size Edge 800

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lavoisier

Winter is Coming!
Location
Kendal Cumbria
Can somebody please help me?

I picked up my new bike today(Specialized secteur Comp) and have just fitted my edge 800. However I'm a bit unsure as to whether to leave the wheel size to Automatic or to enter it manually.

My tyres are 700x25c but can someone explain how the auto wheel sizing works using GPS?

Thanks in Advance

Paul
 

the_mikey

Legendary Member
When using only the GPS to monitor speed, the wheel size isn't needed.

When using the Cadence sensor you'll need wheel size, as this will produce a more accurate report of your speed. You may have already noticed the reported speed can be quite vague using gps, which is fine in general, but not much use if you need accurate information when training.


Auto wheel sizing may figure out what size your wheels are from the wheel rotation data being returned from the cadence sensor crossed with the GPS speed data.

You could also use manufacturer data on wheel size, or measure the length of one rotation yourself using a tape measure, preferrably with your weight on the bike.
 

Svendo

Guru
Location
Walsden
Don't know if the 800 is the same, but on my 705 I used the 'Auto' option for a while, then switched to the custom settting with the reading the auto setting had settled on. I presume it uses the GPS info to work out the wheel size until it's steady then switches to using the wheel sensor for speed.
 

Farky

Senior Member
Location
West London
Don't know if the 800 is the same, but on my 705 I used the 'Auto' option for a while, then switched to the custom settting with the reading the auto setting had settled on. I presume it uses the GPS info to work out the wheel size until it's steady then switches to using the wheel sensor for speed.

I did the same as you can lose the GPS through wooded areas etc and by using the custom setting, you eliminate that potential loss.
 
OP
OP
lavoisier

lavoisier

Winter is Coming!
Location
Kendal Cumbria
:unsure: This may make me sound a bit thick but what's the best technique for doing this?

Paul
 

gaz

Cycle Camera TV
Location
South Croydon
lower the saddle so your feet can touch the ground. position which ever wheel the computer is going on with the valve at the bottom, mark the floor where this is. Sit on the bike and roll it forward until the valve has gone all the way round and is back on the floor, mark the floor at where it is and measure between the two. You will usually need to put MM in.
 
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