When I was in the process of mounting a larger front tire on my ZERO DS I found something rather disturbing. When the motorcycle shop went to remove the innertube from the original tire they found a section of the tube had been twisted around itself one or more times. These two twists had never been able to expand with air pressure. It reminded me of a clown's animal shaped balloons. It explained why there was a slight "unbalance" in my front wheel rolling on pavement even though the tire had balance weights. I was standing right there when this was discovered and I was as surprised as the mechanic.
What this indicates is that the person mounting the tires at the factory had not been trained to always put a little air in the tube before stuffing it in the tire. If the tube is completely deflated it is very easy to accidently twist it or even pinch it between the tire and rim, when installing. I learned this a long time ago with bicycle tires.
My advice to ZERO S & DS riders is this; if you feel even a slight thumping or what feels like imbalance, in either wheel, when riding smooth pavement, take the tire off one side of the rim and check for proper tube placement. I think that had I continued to ride mine, the tube would have eventually failed, and deflated rapidly, not to mention uneven tire wear.
ZERO needs to make sure their tire mounting personel are properly trained to do that job. It is something we, the customer, cannot easily check on.
Trikester