Page 1 of 1

Calibration & Watts

Posted: Sun May 03, 2009 11:47 am
by bob524
Coach

I did what you suggested regarding new coast downs and calibration ride using the same road for the coast downs and a less traveled road for the calibration ride.
Here are the results. Aero .368
Wind 1.182
Cda .311
Fric 1.989
Riding Tilt .2
Crr .00448
These numbers were the result of using all the best coast downs that I have done over several days. The numbers didn't look right just using the coast downs from this last ride.

I did a 22 mile ride the next day after saving the above parameters.. One problem i was experiencing was a drop off to 0 for watts and cadence on the top of a hill and a drop off to 0 for watts and cadence whenever i would stand. Also i thought my average watts would have been higher than 135 for the ride. How is average watts affected by downhills when you are not pedaling i.e. does this reduce the avg. watts number.

Attached is the new calibration ride and the 22 mile i am referring to.

Your comments would be greatly appreciated.

Re: Calibration & Watts

Posted: Sun May 03, 2009 12:06 pm
by coachboyd
If your cadence is not lined up that well, it will drop to zero when you torque your crank. And when the iBike sees zero cadence, then power must also be zero. This would explain the low wattage results.

If you are having problems with cadence going to zero, I would recommend going to Radio Shack and getting a couple of rare earth magnets. Tape them to your crank and you'll have a lot stronger signal to the cadence sensor.

Other than that, your profile and ride file look VERY good.

Re: Calibration & Watts

Posted: Sun May 03, 2009 4:28 pm
by bob524
Coach
Thanks for the info... i'll try the earth magnets...

Re: Calibration & Watts

Posted: Sun May 03, 2009 9:42 pm
by R Mc
re: cadence magnets:

Another option, which I figured out after a) having the supplied magnet slip during a ride and b) deciding that I didn't like zip-ties on my zipp cranks: take a circular spoke magnet (with a shortish tail-side, the ones velocomp supplies are usually too long on the back side) and insert it in the pedal spindle hole on the back side of your non-drive side crank-arm. If it fits, silicon glue it in place. Adjust the cadence sensor to match up with it, and angle it so that it's within 1-2 mm.

You might need to do something similar with the r.e magnets anyway.

(And, should you need to get to that pedal spindle, it's easy to pull the magnet out.)