I have to agree, cost more to build than you can buy one. Hey Bib, what is there about a tire that makes it go flat, I mean it is just a piece of rubber. That being said i picked up 2 tires for my dolly from Harbor Freight and they don't hold air! I put them in water and could see one of them was leaking through the center of the rim, not where the tires seals against it. Tire is probably ok, must be the rims that ****.