The cart was never meant to be used on a daily basis. We did use the cart at home out in the fields before we used it in the parade. The box is built very basic and is not as heavy as you may think. A mountain bike can carry alot of weight without the wheels collapsing.
I am very careful and cautious when it comes to my donkeys. I realize in the picture it may not look as safe as it actually was. I used the cart and felt very stable and safe. I too wondered about the tires when I first got it but after seeing it and using it, I felt it was safe. I also had people walking on front of me and behind me to assist during the parade in the event that something happened.