What about wheels types? The wheels go ’round and ’round. I can’t remember where or when I first heard that ditty, but it must have made a big impression on me. That one line kind of sums it up: if your motorcycle’s wheels don’t go round or if the wheels aren’t round, it’s a bumpy ride indeed.
Most motorcycles roll on either spoked or cast alloy wheels, but some are fitted with composite wheels, or even split rims. Each type has advantages and disadvantages.
Spoked wheels are traditional in look, can be very strong, and are rebuildable. They also need regular maintenance to keep them round and true. Spokes are built up of a rim laced to a hub by spokes. The hub is a casting with two or more bearings in it that rides on the axle.
The brakes are also attached to, or cast integrally, with the hub. Arranged around the periphery of the hub are flanges that have countersunk holes in them to locate the spokes. The rim is the hoop-shaped band of metal that carries and supports the tire.
Traditionally, rims were drilled through their centers to accommodate the spokes, which connect the hub to the rim. Because of all those holes, spoked wheels usually require the use of an inner tube.
A large rubber band or thick tape, the rim band, is placed over the nipples to prevent them from grinding through the inner tube. The tube rests in the well, over the nipples. Some current rims are built to be run tubeless, however, and these have holes along the outside edges of the rim for the spokes.
Cast wheels for everyday street motorcycles gained popularity in the late 1970s, and they are currently popular on all but cruiser-style bikes. They are cast in one piece, usually of aluminum, although magnesium wheels are used on some high-performance machines. Cast wheels can be both light and strong, and they require no maintenance (other than servicing of the wheel bearings).
Cast wheels were originally developed for racing use. The wheels were cast from magnesium and then machined to be absolutely true. The wheels were extremely light, extremely strong, and extremely expensive.
A further advantage of the cast wheel was that it lent itself to tubeless tire use, which the tire manufacturers applauded. They also looked really cool and lots of riders began to demand them for their street bikes.
However, magnesium is a poor material to use on a wheel that sees lots of daily riding. It’s expensive and very prone to corrosion. That’s no real problem for a race bike, but a street bike is likely to see a fair amount of damp and wet weather.
True, magnesium wheels also have a nasty habit of cracking over prolonged periods of time. For those reasons, street motorcycle wheels are usually made of aluminum alloy or even malleable cast iron. As a result, they are generally heavier than the equivalent-size spoked wheels.
Some bikes, most notably Hondas, were fitted with composite wheels built of a cast hub linked to the rim by stamped, star-shaped spoke pieces. Composite wheels can be light and strong, and they require no maintenance, also the rim and/or spokes on some can be replaced if they are damaged.