Speed spikes HIGHER with wired mount

[rruff]

I've experienced dropouts in the speed before, but never this. I recently moved the sensor to the front wheel and I'm getting this weird behavior... the speed intermittently jumps up several mph for a couple seconds and then comes back to normal. Happens a lot. Any ideas on what could be causing extra signals?

[Velocomp]

Either it's a gone-bad speed sensor or improper spacing of the magnet and sensor. The magnet should be 1-2 coin widths away from the speed sensor.

[rruff]

Thanks. The distance looks good, and everything appears to be in the right place. I figured if something was wrong I'd be losing signals, not gaining extra ones. Have you experienced these sensors causing double signals before? Any way to get just the sensor?

[Velocomp]

The reed switches can fail sometimes. We don't have any replacement sensors.

[pjboyle]

rruff...

Since you recently moved the sensor to this wheel (and I assume it worked fine before), it makes it seem like the current physical setup would be more suspect than the hardware. You might try repositioning the magnet slightly, even rotating it 90 degrees. A magnet has a field that is shaped like an hourglass aligned with the two poles. It is possible to have this field aligned so that the sensor can move through the two lobes of the field and the space in between and register a double hit. The intermittent could be from being right on the edge of this phenomenon and stresses and flex on the wheel moving the spoke position enough to make it not constant. Might be worth a try before buying replacements.

PJBoyle

[rruff]

Thanks for the idea... I bet you are right.

Oddly the last two rides (~110 miles) I've only seen one very brief spike, so it's working better now. If it starts acting up again I'll give a reposition of the magnet a shot. I'm using a small niobium magnet that is epoxied to a spoke.