I'm in Montreal, someone at "https://www.phattycycles.com/" is selling 20x4 inch fat tire and studding them if requested.
But still not sure if 20 x 4 tires fit on rad runners (our tires are 20 x 3.3)

Hi! I have a rad runner plus, riding my son to school everyday. But it's starting to be icy and I want to put studded winter tires. But they dont seem to exist anywhere in 20 x3.3 (the tires size that the runner+ comes with). I found 20 x 4.0 studded tires, but would it fit? Thanks for your advice if you have one!