It may be possible to use a 4-3/4 inch wide fender with a 5.00-16 motorcycle tire, depending on how it is mounted, a 6-inch width fender is a better option. This gives proper clearance and allows more flexibility with how you mount it, how close you can get it to the tire, etc. The 6-inch width fender will be able to sit closer to the tire, as the side of the fender won't interfere with the tire tread, and instead will do a better job of keeping road grime and water channeled to the underside of the fender where it belongs!