This is my 27 gallon SmartTote's 3rd year in service. I volunteer at a state park for 4 months each summer so we are talking 10 months service to date. It is approximately 1/3 to 1/2 miles to the dump and I have to dump every 1-2 weeks.
One of the front wheels failed with the rubber "tread" splitting. I looked up the part on Thetford's site:
40528 Double Caster Wheel Kit for 18, 27 and 35 gallon
and then tried to find a "Dealer" that had it in stock with no luck. The best I could find was one source that could order it with shipping in 4-6 weeks for $59.95 plus shipping. 4-6 weeks might as well be totally unavailable since I use this unit a couple of times a month. I talked direct with Thetford with no luck other than I would have to order from one of their dealers (that obviously don't stock replacement parts).
I went to Home Depot and found just what I needed. I had to buy the bracket along with the new 5" wheel, but removed it from the bracket and installed on the existing SmartTote bracket. Since the new wheel is just slightly larger than the original, I replaced both wheels. Total cost was $19.32 for both.
Installation took less than 5 minutes after I had the SmartTote up on a table and had two wrenches in hand. I included a two completed pictures one of which shows the location of the washers that were already spacing the original wheels.
It works perfectly with parts available locally.