Recently while riding home from Seattle a strange behavior occurred. Everything seemed ok for the first few minutes. But then while heading out of the Seattle tunnel over I-90 onto the long I-90 downhill bridge stretch towards Mercer Island, I reached 45kph and was getting speeds displayed that would bounce from zero up to the speed I was going. As this was happening, when it went below the e-assist speed, it would attempt to give me pedal assist at these higher speeds. But just for a second or two. Since I usually pedal going downhill for that extra speed, this was somewhat disorientating.

I wasn’t sure what the deal was, something was obviously off, and as I rode up into the hills I kept getting odd speed fluctuations, even when I was traveling a steady speed. I thought, maybe this is because I’m pulling a trailer this time. Even though that didn’t really make sense.

I rode the 28 kilometers home and set about writing an inquiry to my local bike shop. With a thorough description sent off I went about other activities waiting for a response. In short order I got a response and they asked where the magnet was positioned on the wheel that feeds the speed sensor. I knew what that was, but wasn’t sure how the positioning for it should be. I took a few shots, shown in the grid of images below, and to note – this is the WRONG position.

The informed me where it should be. It should be closer to the sloped from part of the sensor. I grabbed a trusty Phillips and loosened up the magnet and slid it over about 4 millimeters. Back to the trails for a hill climb and decline!

A few minutes later, I’d confirmed, that mere itty bitty little 4mm is exactly what was causing the problem. Whew! Relief. Off to get some more miles in and get some pick ups done! 🤙🏻

Props: Thanks Dandelion Bikes Crew!