You can go up to a 32" diameter tire, and up to about a 285 mm section width (~ 11.5") on a stock X, if willing to trim a bit of plastic inside the front wheel wells, about where the mud flaps screw to.

If the rim is 20", and the total diameter is 32", that leaves about 6" of sidewall, a reasonable amount to help ride better, and avoid pot hole damage, etc.

If you use less than ~ 6" of sidewall height, you will tend toward an annoying number of flats and rim dents, etc.

A 285/50/20 would be closer to 31", leaving only ~ 5.5" of sidewall, a little short.

A 305/50/20 would be ~ 32", but might be a little wide.


A 275/55/20 would fall into your preferred range, and might be your best fitment....at ~ 32" in diameter, and within mm of the 285 mm section width goal.