The rear tire on my 2011 Zero XU got punctured by a long deck screw. I have no idea how it managed to get lodged into the tire, but it certainly made a big popping noise as I was riding along.
In taking things apart to get the rear wheel off, though, I found the answer to the question that had been plaguing me since I bought the infernal bike:
Why does it make a chattering noise like a beaver (particularly at lower speeds with no throttle application)?
I'm not that image conscious, but it is a bit embarrassing to ride up on something that sounds like a Fisher Price Corn Popper. I've been in the habit of keeping the throttle applied at all times just to avoid the sound.
For whatever reason, Zero made some sort of chain guard out of Delrin (or some Delrin-like material).
I presume that they concocted the contraption because they were afraid of the chain slapping the rear arm cross-member that stores the charger cord? I don't think it would normally, but with the chain stretching so easily, maybe it might.
The problem with their implementation is that it is too close to the chain (e.g. negative clearance). At least on my bike (200 miles on the odo), there are deep grooves in the Delrin made by the sides of the chain. So, with each chain link riding over the Delrin, the chain must hop and down a bit... particularly when the motor isn't pulling hard. Voila, chatter.
Delrin has some self-lubricating properties, but surely the extra friction can't help with energy efficiency.
There doesn't seem to be a means of adjustment, and if I manage to cut out a chunk to increase the clearance, there doesn't seem to be enough material left for structural integrity. I'd be afraid of it falling apart, a piece getting lodged between the chain and sprocket, and finding myself getting launched over the handlebars onto the pavement at speed.
I'm not sure that won't happen anyway eventually with the chain grinding away bit by bit.
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Topic: 2011 XU chain guard (Read 991 times)