Compoter wheel size calibration question?

[vegasbabee]

I have a Specialized Turbo bike comp and set the wheel size to default 700x23, which I think is 2096mm. Sheldon Browne's gear ratio calculator indicates that 50x12 @80 rpm should be 28.4 mph and I mycomp registers at 28.2 mph.

Similarly, in a 39x25 test at 80 rpm, I should be at 10mph according to Brown and I get a 9.8 mph reading.

Do I manually need to increase the travel length to, for example 2099mm or shorten it? Thanks!

 

[eric_the_red]

Increase, I think. The computer counts the wheel revs per time period and I guess multiplies this by the inputed size, so if you increase the input you should get a bigger number. You can always do a roll test by sitting on the bike and measuring how far it goes with one wheel revolution. That number, in mm, is usually what gets inputed.

 

[vegasbabee]

I have a Specialized Turbo bike comp and set the wheel size to default 700x23, which I think is 2096mm. Sheldon Browne's gear ratio calculator indicates that 50x12 @80 rpm should be 28.4 mph and I mycomp registers at 28.2 mph.

Similarly, in a 39x25 test at 80 rpm, I should be at 10mph according to Brown and I get a 9.8 mph reading.

Do I manually need to increase the travel length to, for example 2099mm or shorten it? Thanks!

the crux of the biscuit is the apostrophe