I often have customers looking for wider tires for safety or better handling or looks. In EVERY instance what they need is a better tire. Even if you can cram some monster tire in the swing arm and fender well, the narrow rim will distort the tire. The tire will puff up in the center and you will actually ride on a smaller contact patch than if you had the stock tire. Handling and wear will suffer. Lowering the tire pressure will widen the contact patch, but then it will squirm. Corners will get real interesting. You could custom lace wider rims, then re-engineer the fenders and swing arm. $$$$$ In the end, the stock Avon work well for all around use. The Avon AM26 works great to upgrade for the street. For aggressive dirt riding (on an Enfield?) stick to 100/90-19 dual sport tires. The knobs on these are small enough that you probably won't have clearance issues.