Bike hubs come in different sizes. Some are 100mm wide, others are 110 or 120 and so on. The size determines the distance from the dropouts to the center of the wheel as well as to the center of the tire. A 120mm hub will give you more clearance between the chain and the tire than a 100mm one. In most cases, if a narrow hub is matched to the width of the frame between the dropouts, and you want to install a wider hub, it is pretty easy to "spread" the frame to accomodate the wider hub. In extreme cases I have even resorted to using a scissor jack to widen the distance between dropouts an inch or two. One way to cure your problem is to get a wheel with a wider hub or lace a wider hub into your rim and spread your frame a little. Otherwise, you won't be able to overcome your existing geometry with a wide tire.