Wheel Circumference

[bigclick]

Is there a recognised method for deriving the circumference fo a wheel for bike computers ?

Or can anyone tell me what I need to put in for the KTM Macina Lycon with the Nyon computer?

 

[SRS]

Is there a recognised method for deriving the circumference fo a wheel for bike computers ?

Or can anyone tell me what I need to put in for the KTM Macina Lycon with the Nyon computer?

Old fashioned bit of string has always worked for me.

 

[Alan Quay]

....or 2πr

 

[bigclick]

And is Bosch asking for the outside circumference including tyre or just the wheel, I would assume include the tyre otherwise its an unkown variable?

 

[Croxden]

Mark the tyre with chalk or tape also the floor, roll the bike till a full circle has occurred. Mark the floor, then here's the clever bit. Get a tape measure, put it between the marks and depending on your eye sight, you should have it.

 

[bigclick]

2150

 

[Kinninvie]

If thats inches I assume you have a penny farthing

 

[bigclick]

If thats inches I assume you have a penny farthing

Narh it's mm I wouldn't mind trying a penny farthing though

 

[eHomer]

Mark the tyre with chalk or tape also the floor, roll the bike till a full circle has occurred. Mark the floor, then here's the clever bit. Get a tape measure, put it between the marks and depending on your eye sight, you should have it.

I've always found that to be the simplest and most accurate method.

Tyre cross section variables can vary the outside circumference too much to go on rim size "averages" alone.

Also, if you're really picky, it's best to sit on the bike too when making the floor marks, because the rider weight reduces the radius by a few millimetres at the point of contact, thus reducing the circumference by an inch or so.

I use a Garmin GPS watch as well, and setting the computer wheel diameter that way gets the total run length to agree within a tenth of a mile on a 24 mile ride.