So my son has this little Tykes Bikes 20" aluminum fat bike. The stock tires were ridiculously heavy and stiff to the point he could ride it with almost no pressure... I dub named them the 'Run-Flats'.
So searching for tire options, most are not available in 20" therefore pickin's are slim. On a whim, I decided to order a couple of specialized tires that are 2.8" and see what would happen. I have a friend running a 3.0 on a 60mm, so I thought I'd give it a shot....
Well, it surpassed our expectations! Aside from the benefits of a better made tire, they are about 680g wire bead which is way better than the 3.3lbs monsters that were on there. also the tire seems to actually flex and track nicely for him over rocky and loose terrain, unlike the run-flats that would transfer most of the bumps up through the bike.
So, if any of you thought about running a smaller plus size tire on your fatty rims, it can be done. I would imagine the benefits he sees would transfer over to the larger bikes.
Here are some pics of the build:
