Interesting behavior - logging miles on car

[jim_s]

This is not a 'problem' per-se, but its interesting, and the Velocomp guys may want to know if they're not already aware of it.

I rode several miles home from work on Friday (w/ a trip reset before leaving work), then the bike sat in the garage until this morning (Sunday), at which point I put the bike on the roof rack and drove several miles to the start of a ride. Part way through the ride, I was surprised by my mileage and realized I'd forgotten to do a trip reset before the start of the ride. (did my tilt and offset calibrations though - important things first! At any rate, the mileage difference was more than my commute home on Friday would have accounted for, and when I got home and downloaded the ride file, there was a 6.5mi stretch w/ zero power and zero wheel speed, but with wind speeds averaging 18mph - clearly the trip on top of the car, but also clearly the wrong distance. Only two possibilities I can come up with were that A) the wheel magnet happened to be right beside the pickup while on the car, and somehow had the iBike logging data despite no wheel speed or B) it for some reason saw the wind speed and assumed it should be on. I rolled the bike to the car, so the iBike as undoubtedly 'live' when I drove off w/ the bike on the car.

Any insights or ideas on this? (its mostly just a curiosity!

[travispape]

I'm surprised that you got 6.5 mi of mystry miles if the wheel speed was zero. I'd be curious to look at the file if you want to upload it.

Travis

[jim_s]

Travis - attached is the ride file from yesterday's ride. It says 8/1/2008, but that's because I didn't do a reset following a short trip on Friday afternoon. The section near the beginning w/ the wind-only will be pretty obvious.

Thanks for looking at it - Not sure if this is a 'bug' per-se or what, but it is kind of interesting!

Jim

[travispape]

Right, I'm just curious too.

Actually, what you have there is wheel-only data--no wind. Is there any chance that the wind was spinning the wheel as you drove? Otherwise, it might be like you said an the magnet was just on the ragged edge of being detected by the sensor. As the bike was buffeted by the wind, perhaps the magnet was moving just enough for the iBike to count "magnet ticks" and register that is speed.

Travis

[jim_s]

Hey, you're right - I was confused in looking at the ride file - it was the wheel I'm seeing, not the wind. In that case, it must be that the wheel magnet just happened to be near the pickup. I've got a roof rack where the wheels are held stationary, so it wasn't a case of wheel spin, but the front wheel does tend to wiggle back and forth a little bit, so its got to be that the magnet was triggering the pickup.

Mystery solved - sorry for the confusion on the wind vs wheel pickup.

Jim