Hello fellow laser sailors! In my quest to repair my Seitech dolly tires I gathered knowledge. Now I will share my discoveries. I have the tubeless knobby Carlisle 145/70-6 tires on older fiberglass/plastic type redish, pink wheels. The air pressure got low and caused cracks to appear in the sidewall. I attempted to put a strap around the tire and force high pressure air into the tire, in hopes of resealing the bead, but the cracks were too deep. This works for some people, however my tires are showing considerable age. Here's the options I discovered after searching the internet: A) $125+ Buy two new Seitech wheels with tires installed from APS or WestCoastSailing. B) $60+ Buy two new replacement tires from an online ATV dealer and attempt to wrestle the tires off of the rim or have a tire shop remove and replace them. C) ~$20 Remove valve cores and pump fix-a-flat slimey goo into the tires, then place them on the axel and spin them around and hope that all of the cracks and leaks get sealed. D) $21 Purchase and insert an inner tube into each tire. Being a handy guy, I chose the cheapest and most reliable option and replaced the inner tubes. It was VERY easy and took less than 15 minutes once the tire shop broke the tire bead. Step 1 - Take your wheels off your dolly and bring them to a tire shop. They put the tire into their press after removing the valve core. The press, pushed the sidewall toward the center of the tire and after a few seconds and a loud "pop" the bead was broken. The tire shop did this for free. Step 2 - Buy new inner tubes. I went to Home Depot and bought Slime Smart 6" Wheel Barrow Inner Tubes that fit a 4.10/3.50-6 wheel, Slime Part #30011. I thought they'd be small, but they fit perfect. Go to www.slime.com they have them for sale their too. Step 3 - Cut old Valve stem off wheel. From inside the wheel take any sharp object, knife, chisel, razor blade, etc.. Cut half way through, then a slit on the side and you can then pry out the stem from the outside of the wheel. Step 4 - Insert new inner tube. Put the valve stem through the hole in the wheel first. Then use a wooden paint brush handle, or something similar that won't cut the rubber, to push the inner tube inside the tire and work your way around the rim. Use a prying motion to get the inner tube completely inside the tire. Step 5 - Inflate inner tube. Clamp vice grips onto the valve stem, so that it doesn't get lost inside the wheel, nor get pressed into an odd angle once inflated. Using an air compressor, give five or six short bursts of air to ensure the tube inflates evenly, then use continuous flow. At about 15 psi the inner tube will push the sidewall out to the bead. You will hear a loud "pop". I continued to inflate to 28psi. You may want to seal the hole in the rim with silicone or RTV, so that the valve stays in place in case of a loss in pressure. It will also keep protect the inner tube from corrosion. I did not do this yet. And you're finished! Ready to roll! Happy Laser Sailing!