Quote Originally Posted by Bloodsng
http://www.marathonind.com/solid.html this site has a new type of tire that some of the guys I know use and they seem happy with them

Blood
There's another version at http://www.airfreetires.com/. I know a commuter who used these. They don't get flats, but they are heavy, and they are a bear to get on the rim (the company provided a tool to do it). To quote Sheldon Brown:

"Of all the inventions that came out of the bicycle industry, probably none is as important and useful as Dr. Dunlop's pneumatic tire.

Airless tires have been obsolete for over a century, but crackpot "inventors" keep trying to bring them back. They are heavy, slow and give a harsh ride. They are also likely to cause wheel damage, due to their poor cushioning ability. A pneumatic tire uses all of the air in the whole tube as a shock absorber, while foam-type "airless" tires/tubes only use the air in the immediate area of impact."

The guy I know who used them broke a rim.