There’s another factor that comes into play when selecting tire sizes, and that’s style. People like the look of a bigger rear tire, and might even assume it’s going to give them more grip. But putting a bigger tire on a given rim doesn’t guarantee a bigger footprint. Tire profiles are designed with specific rim widths in mind, and in some cases putting a wider tire on narrower rim can pinch the tire so much that the contact patch becomes smaller. Plus, it might rub on your swingarm, throw off your bike’s geometry and speedometer, reduce your gas mileage, and make your bike handle worse. But hey, if you think it looks cool, good for you.