Intuvia wheel circumference issue

[Brian Park]

Hi again

This issue is more about the limitations of the intuvia unit when decreasing the wheel circumference.
My bike has skinny tyres that are 1710mm in circumference. The intuvia unit that comes with the bike will only allow me to decrease the circumference to 2140mm. I'm guessing it's been calibrated for a 29inch wheel mountain bike with fat knobblies, not a hybrid with 700cc tyres.

Obviously this means my assist cuts out a little sooner than normal and the readings will all be, to an extent, inaccurate.

What to do? Any ideas?Is this something anyone else has had experience of?

 

[JoePah]

HI Brian,

Are you sure you have a 700c tire?

Here's circumferences for different 700c tire sizes:

700x28 2130 mm
700x35 2174 mm
700x44 2230 mm

The sure fire way to measure the circumference of your tire is to roll out one revolution of your bike tire on the floor and measure the distance travelled with a tape measure...

Or just use the bike cadence calculator
http://www.bikecalc.com/wheel_size_math

 

[Brian Park]

Thanks for this - on paper my tyre is 700c x 42mm but measurement of the outside circumference when marked and ridden over a flat floor gives me a measurement of 171cm. I will check again but have already checked it twice so now I'm more confused than ever

 

[JoePah]

mmmm.. Maybe youre not rolling out in a straight line?

Make a length of string taut and tape it to the floor and roll the tire next to the string.

 

[Chris Nolte]

Just a FYI - you can only adjust the wheel circumference + or - 5% with the Bosch system. This prevents users from achieving power at more than the intended speed.