Baja 5B tires are among the most difficult to stretch over their rims. Use a technique similar to that used to mount full-size tires, but instead of a machine, you’ll use the flat handle of a spoon. Insert the handle under the lip of the tire to pry it up and over the rim. Work the handle all the way around the tire until the entire bead is in position. A little hand soap on the handle may help it slide around more easily.
Tip by Bart Wheadon