This doesn't work.
You can do it, but it doesn't work.

The whole point of running fatter tires is that you can run them at lower pressure, so they absorb more road shock. If you mount fat tires on narrow rims, then you have to keep the fat tires inflated very high just to keep them from squirming from side-to-side and handling poorly. And if you inflate them very high,,,,, then they're not going to absorb road shock like you wanted them to do. So if you mount fat tires on skinny rims and over-inflate them, all you end up with is fat tires that ride just as hard as skinny tires would have, but that weigh more than skinny tires.

If you want to run wider tires, do yourself a favor and get wider rims. The fat tires will ride and handle well at the lower pressures they're intended for. You cannot "make" fat tires work properly on skinny rims.
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