Motorcycle Wheels & Suspension
Though most spoked motorcycle wheels appear to be almost identical in construction, there are subtle size variations that enable designers to custom tailor wheels and tires to the intended purpose of the machine. On the other hand there are also almost as many cast and pressed metal wheels as there are different models of motorcycles!
Sizes, Types and Application
The diameter of wheels and tires, measured at the bead, varies from as little as 16 inches up to 23 inches. The rims themselves may be of either steel or aluminum alloy.
Tire widths range from 2 inches to darn near a foot in some chopper rears, and are accommodated by rims from about 1 1/2 to 4 inches wide... at least for anyone not trying to mount a 330 rear.
Spokes are available in several diameters and range in length from 6 inches to more than a foot. Additionally, spokes may be "inners" or "outers" as well as "lefts" or "rights." That is, a single wheel may have as many as four different types of spokes.
Spoke patterns vary according to the size of the machine and the strength required. Smaller cycles generally use 36 spokes while larger machines have 40 spokes. The spokes are attached at various tangents to the inner hub and are fixed to the rim by threaded nipples. Wheels can be made stronger by altering the spoke pattern from the simple radial array to a criss-cross pattern.
Remember that your motorcycle is literally hanging from the top spokes of your wheels. If the spokes are loose, absent, or incorrectly installed, serious consequences may follow. A series of loose spokes on one side of the tire will soon work the spokes loose on the other side of the wheel. If you discover loose spokes, tighten them immediately.
Many motorcycles use cast aluminum or magnesium wheels. The main reason for using this expensive type of wheel is that it is strong, light, and perfectly true, since it is finished on a lathe.
The sizes of wheels and tires selected for a motorcycle usually depend on the bike's general size and weight class. Smaller motorcycles up to 250-cc street machines tend to use 17-inch or 18-inch tires. Middle weight 250-800-cc street machines tend to use 18-inch tires fore and aft, while heavyweights over 800 cc use a large 18-or 19-inch tire on the rear and a 19-inch on the front. Of course when you enter the high end chopper, cruiser or tourer market, all sorts of bizarre wheels and tires are used.
Enduro and Motorcross bikes lean toward the larger 21 to 23-inch front wheel assembly to ease rolling over obstacles. Smaller, slower trail bikes, get by with an 18-inch front tire, while dirt bikes of all types are generally backed up by an 18-inch knobby or trials universal.
Tread design and selection is based on the intended use of the machine. A full-fledged dirt bike used exclusively for Enduro, Motorcross, or trail riding, relies on rough knobby tires for traction in mud and loose dirt. On pavement, however, these tires lose their charm and their traction. Besides wearing rapidly (often in less than 1000 miles or 1600 km) knobby tires are poor on dry pavement and extremely unpredictable on wet pavement. Avoid using them on the street if possible. The dual-purpose street-trail machine is often found with trials universal or semi-knobby tread tires. This tire is meant to feature the good traction of a knobby in the dirt while keeping the road manoeuvrability of a street tire. Although it is a good compromise, it does not perform as well as either a street or dirt tire when needed.
Street riders are deluged with a barrage of individual patterns of road tires. Tire technology has advanced to such a degree that most road riders won't be able to tell the difference between one tire and the next, unlike the bad old days when ribbed front tires would follow the rain grooves in the pavement... whether the rider wanted to go in that direction or not!