Well I spoke to soon on my DNA mammoth 21x3.5 it is leaking air in one week it lost about 6 lbs. I didnt know to run a tube for a cheap insurance. So I was looking around my shop for a small air chuck to fit between the spokes no luck finding it so I took the large one ground down both sides left and right to make it fit and give myself a little wiggle room so I dont scratch the wheel.Then I was thinking if I get out somewhere and tire goes low I would be in trouble if the gas station has no small chuck. So I took a valve stem and jammed the air chuck down inside it as far as I could get it and then some so now I have a adapter to fit the big air chuck.

This may not be the prettiest thing to look at but it will do in a jam for sure it works I have used it a few times. I plan to make another one to keep in the shop and keep one in my tool box on the bike or maybe next to the battery

 

Necessity is the mother of invention.
Pretty cool thingamafixer.