There’s something enchanting about gliding down the asphalt on a sleek, silent road bike. The rhythmic hum of the chain, the whoosh of the wheels, and then… the squeak, click, or crunch that breaks the reverie. If you’ve ever found yourself wondering why road bikes make noise, you’re not alone. Unwanted sounds emanating from our beloved two-wheelers can be frustrating, mystifying, and sometimes downright annoying.
Freehub Mechanism & Pawls Cause Noise
The noise emanating from road bikes is often due to the freehub mechanism and the pawls interacting with each other.
When a cyclist is coasting, the spring-loaded pawls move over the ratchet teeth, creating the distinctive buzzing or clicking sound.
This sound can vary in intensity depending on the design and construction of the hub. Specifically, hubs with more pawls tend to be noisier as more engagement points lead to faster engagement when pedaling.
Additionally, the type of lubricant used inside the hub can also influence the noise level. Thicker oil or grease might dampen the sound but may also be less efficient in terms of energy transfer. [1]
These sounds made by various bikes manufactured by different manufacturers may vary in volume and tone but are generally not indicative of any issues with the bike itself. [2]
Pawls Click Into Place When Not Pedaling
As mentioned above, the noise is caused by the action of pawls, small curved levers that engage with the teeth of a cogwheel allowing it to turn in only one direction. These pawls are crucial to the movement of the bike’s freehub, which determines how the gears work.
When a cyclist stops pedaling, the pawls click into place across the cogwheel, producing the familiar clicking sound.
This action is similar to that of a ratchet wrench, which remains quiet when force is applied but makes noise during its resetting motion. [3]
Different Freehub Designs Make Different Sounds
Freehub designs play a significant role in the noise a road bike produces while coasting.
Higher-end freehubs tend to be louder due to factors such as the type of lubricant used, tension on pawls, and the number of engagement points.
High-performance freehubs often use lighter oil or less viscous grease, which reduces resistance and can lead to increased noise levels.
Furthermore, these freehubs also have more pawls and engagement points, resulting in faster response when pedaling but also creating added noise as the pawls interact with the engagement surfaces. [4]
Although They Make Noise, But Freehubs Prevent Spindle Damage
Freehubs are an essential component in modern bicycles, particularly road bikes.
They not only allow the rider to coast without pedaling, but they also play a crucial role in preventing damage to the wheel spindle.
Shimano, a leading bike component manufacturer, originally developed and patented the freehub design.
This innovative design replaced the traditional freewheel mechanism, which was an integral part of the sprocket set and screwed onto the rear hub.
This unique freehub design allows for smoother and faster gear changes while maintaining compatibility with various sprocket brands.
The ingenious design of freehubs places the wheel bearing outboard of the sprockets, as opposed to inboard bearings seen in older freewheel systems.
This placement significantly reduces the shear force exerted on the spindle when riding over bumps, ultimately preventing potential breakage.
Noise Can Be Seen as Sign of Affluence
Interestingly, certain noises can be seen as a sign of affluence in the cycling community.
High-quality wheels and components can produce distinct sounds that set them apart from less-expensive alternatives.
For instance, the clicking noise from a wheel’s freehub can be amplified on high-end carbon fiber wheels like Zipp, making it more noticeable as the cyclist coasts.
This association with affluence could boost a cyclist’s confidence or simply serve as a reminder of the premium materials and technology they have invested in their bike.
The sound of a loud freehub (if that’s the case) has nostalgic appeal for many and may signal affluence.
However, while some may find these noises appealing, others could find them annoying and distracting. [5]
Noise Can Alert Walkers from Behind
One of the benefits of a noisy road bike is its ability to alert walkers and other pedestrians when the cyclist is approaching from behind.
The sound emitted from the bike’s freehub, particularly when coasting, can act as a natural warning signal for those sharing the path or road.
This convenient auditory cue allows walkers to be more aware of their surroundings, reducing the likelihood of potential accidents and ensuring a safer environment for all road users.
