Bicycle Spokes play a crucial role in a wheel. Because they do such a good job, spokes are often ignored, until, that is, they start failing. This causes the wheel to lose strength and integrity and eventually your bike can become unrideable.
What are bicycle spokes?
Bicycle spokes are the thin rods that radiate from the hub to the rim.
One end is splayed out and that sits in the hole in the hub.
The other end has a thread and this attaches to the nipple that passes through the hole in the rim.
As the spokes in a wheel are the same length, they keep the hub in the centre of the rim and because they are very tight, they keep the rim round. Each spoke is roughly the same tension (tightness) in any given wheel and that tension is adjusted and fine-tuned by tightening and loosening the nipple at the threaded end of the spoke.
The end of the spoke that is attached to the splayed part is either hooked (j-bend spokes) or straight (straight pull spokes).
Types of bicycle spokes
J-bend spokes. Many hubs are compatible with this spoke. The “elbow” is the weak point and is often where the spoke breaks.
Straight pull spokes. They are lighter and less prone to breaking, but truing and building is more difficult because the spoke can spin.
Spokes can be made of a number of different materials, but the most common is stainless steel. It offers strength, flexibility and lightness. Stainless steel spokes come in different profiles:
Plain gauge. Budget spokes that have less flexibility than butted spokes. These spokes are the same thickness all the way along.
Single butted. Fatter at the hub end then the same gauge for the rest of the spoke. This strengthens the spoke at the weakest point. These are not common, but are the cheapest of the butted spokes and good for the wheel builder as they can be shortened and have a thread rolled on the end.
Double butted. Similar to the single butted spokes but with additional strengthening near the nipple. Further strength is added by the middle part being thinner and therefore more flexible. These spokes are thicker at the elbow and near the thread and narrower in the middle.
Triple butted. They have an extra thick gauge near the hub end to further strengthen the weakest point. They are stronger but heavier than double butted and are designed for long distance touring, some mountain biking and Clydesdales.
Bladed. They are flattened in the middle and are generally stronger than butted spokes because a further forging process is applied. Not only are they strong but also more aerodynamic. When they are fitted, they have a tendency to twist, losing their aerodynamic advantage, so they need to be held in place with a bladed spoke holder or an adjustable spanner.
Lacing of bicycle spokes
To create a wheel, bicycle spokes are fitted in different patterns.
Cross pattern. This is the most common lacing pattern and uses the spokes to optimise their inherent strength and flexibility.
0 cross/radial. This gives the lightest wheel because this build uses the shortest spokes. It is used on front wheels as the spoking pattern means that there is less flexibility in the wheel.
Exotic lacing. This is where the spokes are built in less traditional patterns to create a pleasing, aesthetic effect. Crow’s foot and snowflake are two examples.
Attaching spokes to the rim
Most spokes have a threaded end that goes through the rim and attaches to the nipple, a threaded nut. The wide part rests in the rim spoke hole and the rest pokes through. It has four flat sides and a spoke key can slot around this part of the nipple to easily allow the spoke to be tightened or loosened.
Thread. As the threads vary slightly between manufacturers, it is a good idea to buy the nipples with the spoke to ensure compatibility.
Size. Where the spoke key slides onto the nipple can vary in thickness. If you are fitting spokes to many different wheels, you will need to invest in either a variety of different sized spoke keys or a universal one that has the different sizes in one tool.
Length. The length of nipples varies from 12mm to 16mm. This means that if you have a deep section rim, a longer nipple will make it easier to fit.
Material. Spoke nipples are made of aluminium or brass. The brass ones are slightly heavier, but less likely to round off when using a spoke key.
Length of bike spokes
Even the strongest and best built wheel won’t last forever and spokes can break. But it’s not all bad news. If one spoke breaks and the problem is identified quite soon after the event, a new spoke can be fitted and the wheel tensioned again.
As spokes come in various lengths, it is important to replace them with the ones matching the measurements.
A J-bend spoke is measured from the middle of the bend to the end of the thread
and a straight pull from the splayed end to the end of the thread.
The measurement is expressed in millimetres to the whole millimetre.
Even if two wheel diameters were the same size, there is a good chance that the spokes will be of a different length. The following are factors that determine what length of spoke your wheel needs:
- Size of hub flange
- Diameter of rim
- Number of holes in the hub or rim
- Hub diameter
- Number of crosses in the lacing pattern
- In the case of a geared rear wheel, which side the spoke is on.
-The chain falling off behind the rear sprockets and the friction causing the metal to wear away on the spokes making them weaker and more likely to break.
-A crash or impact, especially sideways.
-The thread at the spoke end loosens on one or more of the spokes changing the tension of the wheel and putting pressure on the other spokes.
Age. As the rest of the wheel wears out, so do the spokes.
-If you are breaking spokes regularly and there is no concrete reason, then it is probably time to buy a new wheel or have the old one rebuilt.