Anatomy of a bicycle wheel

Replacing the wheels on your bike is one of the most cost-effective upgrades you can make. Your bike will climb, run and stop better with a lighter wheelset.

Bicycle wheels generally consist of 4 main components: the rims, the hubs, the spokes, and the spoke nipples.

Tires

The part of the wheel that the tire fits on are the rims.

There will be several small holes to put the spokes in and a larger hole for the tire valve. On more expensive rims, the spoke holes may also have brass grommets to strengthen the hole and distribute the load.

On road bike wheels, the sidewall of the rim will have machined braking surfaces. The braking surface sometimes has a groove (a ‘wear indicator’).

Most modern MTB wheels use disc brakes. The brake disc will be bolted to the hub.

Materials and tire construction

Generally, bicycle wheel rims are made of aluminum. During manufacturing, the aluminum rim is extruded and then cut into pieces. These lengths are folded into circles and then the ends are pinned together.

Lighter wheels mean your bike will accelerate faster and climb hills easier. Some cheaper bikes will use steel for rims and hubs. Steel wheels are heavy and wet-weather braking can be poor.

High-end triathlon and time trial wheelsets often use carbon fiber in their construction.

hubs

The central part of the wheel is the hub. The bearings that allow the wheel to rotate are housed in the hub. The axis also passes through the center of the hub. The spokes of the wheel are tied into holes in the hub flanges.

spokes

Spokes are basically pieces of wire with a thread on one end and a bend (the ‘elbow’) on the other.

The cheapest spokes are plain steel. Stainless stainless steel can also be used to reduce weight.

To decrease the weight of the spokes, more spokes can be ‘butted’. This means that the spoke is thicker at the ends (where most of the stress occurs) and narrower in the middle.

Aero wheels will use flat bladed spokes to decrease air resistance. Flat spokes cut through the air better than round spokes.

The more spokes a bicycle wheel has, the stronger (and heavier) the wheel will be. The fewer spokes a wheel has, the lighter and more aerodynamic the wheel is. The number of spokes ranges from about 20 (a front wheel suitable for racing) to 48 (a rear wheel suitable for traveling with very heavy luggage or a tandem bike).

The greater the number of spokes, the longer the spokes must last before breaking: the stress is shared between more spokes.

spoke lacing patterns

Spokes fit a wheel in various patterns. The most common is the 3 or 4 cross pattern. This means that each spoke intersects with 4 or 4 others between the hub and the rim.

In a radial spoke wheel, the spokes do not intersect with each other, which allows you to use fewer spokes and saves weight. Usually only the front wheels use radial spokes, and usually only on performance bikes. A rear wheel with radial spokes would not effectively transfer torque from the sprocket to the rim.

Some high performance rear wheels use a different spoke pattern on each side, for example radial spokes on one side and 2 crossed on the other – the crossed side transfers power to the rim.

So if you want to improve the performance of your bike, choose the best set of wheels you can afford…

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