I needed bigger wheels on my cooler to be able to use it on the beach and carry some extra stuff on top of it for camping (Hammock's Beach, NC). I considered making a beach cart, but this was a cheaper option for me and hopefully will take up less space in my car. I hope someone can give me some ideas on how to make an even better version in the future. I already have some ideas...
The costs include a $30 Coleman cooler from Wally World (Walmart), two 10" pneumatic tires from Northern Tool at $10/each, $3 worth of 1" schedule 40 PVC, $3 for some bathroom caulking, $2 for two cotter pins, and $10 for a 3' piece of 5/8" zinc platted steel rod from Lowes. I like the cooler for camping because it holds ice a long time, so I figured an up-fit would allow for me to use the big tires on the beach and the factory tires for my everyday activities.
I thought about buying the big grey beach wheels, but they were $50 to $60 each.
6/24/2013 - UPDATE - My version of this cooler doesn't fit through a lot of doors really easy, so if you fill it up at the fridge or indoors you may have to pick it up to get it out of the house. I'm probably going to do a modification on a different cooler that will fit through doors for my family style vacations (see the version in the comments section - thanks to the commenter for sharing their version). The one disadvantage I see to the longer cooler is that you will have to bear more of the weight of the cooler while dragging it. If you are going to drag a cooler for a long distance, the version of the cooler that I show in these pictures may be somewhat easier to move. I'll hopefully have the chance to verify this when I test out a modification to another cooler.
Step 1: Cooler with factory wheels removed and drill holes marked
I popped off the factory wheels, and measured on the cooler where I wanted the wheels. The wheel location had to allow the cooler to sit up straight normally while providing the maximum clearance when the cooler is being rolled. The holes had to be drilled to only put a hole on either side of the cooler, without hitting the internal walls. I wanted the PVC carrier pipe that I put in the holes to fit snug against the inside walls also.
You can see my measurements on the cooler, and I used a 1" drill hole punch to put in the holes. I pushed a piece of 1" schedule 40 PVC through the holes to create a carrier pipe for the rod that I used to mount the wheels to. I caulked around each side of the holes that were punched through the cooler, even though it was a very snug fit.
I cut the steel rod for the tires to a length that fit best for my use, and drilled a hole in each side to allow for placement of the cotter pin.