Originally Posted by
Doc_Wui
I agree. There must be a washer missing. You need more room to get the chain over the smallest cog. Maybe the axle is pressing too hard on the sensor. It's amazing how they can measure cadence with that.
I wondered myself.
Here's how. So the 'width of a nickel' spacing sounds about right and if that is off it might indeed mean that the wheel is crooked in the dropouts or that the area has collected grime or dirt. That's what I would check before assuming anything is broken.