if you can get them foam filled, the reliability shouldn't be an issue. If it will fit, fun-noodles can be substituded for proper filling(just don't let them sit on the ground when not in use or they'll deform)
Carefree tires are also great
http://robotcombat.com/marketplace_carefree.html
rims and lots of other nice parts are at
http://robotcombat.com/marketplace_wheels.html