I've got a Go-Go Bike with 12.5 inch wheels. It seems that the tubes don't hold air very long. Is it just that such small tires/tubes were never intended for a 185 pound rider? Does anyone have any recommendations for tires/tubes?
I bought some airless tires, but I'm having a devil of a time installing them. Does anyone have any experience with airless tires on small wheels?
And finally, does anyone think that there would be any issues trying to put a 3-speed hub in such a small wheel? There's already not a lot of room for the pump head between the hub and the valve stem (another reason why I bought the airless tires).
I have a Mobiky with 12½ x 2¼ size wheels, ISO size 203mm. I am guessing this might be the same size. You should be careful designating wheel sizes as there is a difference between decimal and fractional sizes. The fat tires give a nice cushy comfy ride. I suspect the airless tires are much less comfortable. I doubt your air leakage had anything to do with tire size or rider weight.
The Mobiky does have a 3-speed hub and the tubes have bent valve stems for easy pump access. I suspect the bent valve tubes are readily available, but I'm not sure where. Maybe a scooter parts supplier rather than a bike shop.
Other possible issues with the 3-speed hub are number of spoke holes and obtaining the short spokes you would need. Availability of rims in the 203mm size is very limited. If you can't get a 3-speed hub with holes that match your rim you might be able to order a 28 hole rim, or a 28 spoke built wheel with a 3-speed hub, from a Mobiky dealer. I ordered custom cut spokes from my LBS. They were able to do it, but it was not easy for them because the spoke cutting machine is not designed to work with such short lengths.