A too wide tire on a narrow rim pinches the bead together. This makes the sidewall angle inward for poor support and allows the tread portion of the tire to wander in relation to the rim. To compensate for the squirmy feel while riding, tire pressures are increased until it stops feeling squirmy. The result of tire pressures too high is advanced wear at the center of the tire tread, which allows it to square off and start looking like a car tire. Then when leaning over in turns the squared portion nearer sidewalls changes how the bike handles, requiring more and more counter steer in corners as tire wear increases. This progression of events taught me to keep the stock tires sizes on my Honda’s, as more expensive bigger tires only benefit the tire salesmen profit margins both in initial cost outlay and shorter replacement intervals. The argument that bigger tires create a larger contact patch only applies to rims widened along with the tire tread width, as pinching the bead together increases the crown radius of the tread, which along with higher tire pressures, reduces contact patch of the bigger tire (when new) as well as the poor wear patterns described above. I have learned to stick with the stock tire sizes (or as close as I can find, even if I have to order them from afar) when keeping the stock rim on my bikes. I like the neutral handling the bike had when new, and I like it to stay that way for the life of the tires.
