# Mountain Biking - I'm confused about bike comp calibration...

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JasBike
07-21-03, 09:22 PM
i have a Cat Eye Enduro 8...

i mounted the magnet/sensor, set the circumfrence... but what i dont understand is how does the computer know where the magnet/sensor are located on the wheel? wouldnt the readings be different if the magnet/sensor was on the very bottom of the wheel vs. at the very center of the spokes?

or am i just being insanely stupid and missing something..

Pman
07-21-03, 09:32 PM
One roation of thee wheel is one rotation of the wheel at any point. So it does not matter where the sensor is positioned.

JasBike
07-21-03, 09:34 PM
how exactly do the comps work..

Rich Clark
07-21-03, 09:49 PM
The computer counts revolutions of the wheel, and computer has a clock.

If it knows the circumference of the wheel, it knows the distance that wheel covers in one revolution.

If it knows how long it took to cover that distance, if can calculate your speed.

That's it.

RichC

Cyclone
07-21-03, 09:49 PM
It can tell how fast the wheel is turning. The manget part that you put on the spokes only fits in one position on the wheel. If you try to push it down any further or up more it will bend the spokes. Then you enter into the computer what size your wheel is and it's programmed to know how many times the wheel rotates a second

JasBike
07-21-03, 09:50 PM
it.. bends spokes?

AquariaGuy
07-21-03, 11:06 PM
Like what Rich said. All it needs is circumference and the rest is basic physics.

JasBike
07-21-03, 11:21 PM
but the speed at which the magnet makes a full rotation would vary depending on its position the wheel...

07-22-03, 08:20 AM
remember you put a number into your computer when you set it up? It was something like 2012 or some other four digit number. well that number is the length around the outside of the tire. That is why they have different number for different wheels.

And that magnet just counts the RPM or wheel speed not the distance it is going.

JasBike
07-22-03, 12:39 PM
remember you put a number into your computer when you set it up? It was something like 2012 or some other four digit number. well that number is the length around the outside of the tire. That is why they have different number for different wheels.

And that magnet just counts the RPM or wheel speed not the distance it is going.

i get it...

btw nice avatar

JasBike
07-22-03, 12:45 PM
so the magnet/sensors position on the wheel doesnt matter?

RegularGuy
07-22-03, 12:51 PM
Originally posted by JasBike
so the magnet/sensors position on the wheel doesnt matter?

Not at all. The magnet will pass the sensor once per wheel revolution whether it is mounted at the rim or the hub.

Rich Clark
07-22-03, 01:33 PM
Originally posted by JasBike
so the magnet/sensors position on the wheel doesnt matter?

No. It counts revolutions of the wheel. The speed is calculated based on time divided by number of revolutions, with the circumference number telling the computer how far you go per revolution.

If a wheel were 600 inches in circumference and it rotated 60 times in one hour, you would be going 10 inches per hour.

RichC