Why Are BMX Hubs So Loud? A Look at the Engineering Behind Noisy Bicycle Hubs

BMX hubs are known for being extremely loud when coasting. The loud clicking or buzzing noise is a signature sound of BMX bikes that riders have come to expect. But why exactly are BMX hubs so much noisier than other bicycle hubs?

The reason lies in the internal design and engineering of BMX hubs. While they may look simple from the outside, inside a BMX hub contains precision parts and mechanics that generate the loud freewheeling noise.

Understanding the Role of a Bicycle Hub

First, it helps to understand the basic components and function of a bicycle hub.

The hub sits at the center of the wheel and provides an attachment point for the spokes. Inside the hub shell are bearings that allow the hub to spin freely on the axle.

On the right side of the hub is a freehub mechanism that allows the rider to coast without pedaling. It contains ratchet and pawl systems that engage when pedaling to turn the wheel, but disengage when coasting to allow free rotation.

Standard road and mountain bike hubs have quiet freehub mechanisms. But BMX hubs contain specialized designs that maximize noise.

Key Differences in BMX Hub Design

There are a few key differences in how BMX hubs are engineered compared to standard hubs:

More Pawls

• The ratchet and pawl system is what creates the clicking or buzzing noise in a freehub.
• Pawls are small, spring-loaded mechanisms that engage with the ratchet teeth when pedaling.
• More pawls engaging at once generates louder clicks.
• BMX hubs have up to twice as many pawls as a standard hub, often 16-24 vs. 6-12.

Larger Pawl Overlap

• Standard hubs have minimal overlap between pawl engagement.
• BMX hubs are designed so pawls overlap extensively, engaging multiple teeth simultaneously.
• This results in more simultaneous clicks and louder noise.

Aluminum Pawls

• Most hubs use steel pawls. But BMX hubs often use aluminum pawls.
• The lightweight aluminum hits the ratchet ring with more force, amplifying the sound.

Stronger Pawl Springs

• BMX hub pawls have stiffer, stronger springs than typical hubs.
• This results in the pawls snapping against the ratchet ring aggressively, creating louder clicks.

Larger Ratchet Ring

• The ratchet ring has the teeth that the pawls engage with.
• BMX hubs have a wider diameter ratchet ring with more teeth.
• More teeth spread over a larger surface area means more clicks per revolution.

Positioning Within Hub

• In BMX hubs, the ratchet ring and pawls are positioned closer to the outside of the hub shell.
• This allows the sound to resonate and magnify as it reverberates within the larger hub body.

Engineering Considerations for Noisy Hubs

While loud hubs have become expected in BMX, the noise is not without drawbacks. Excessively loud hubs can lead to premature wear, affecting performance and longevity.

So BMX hub engineers must find the optimal balance between maximizing freewheel noise volume while maintaining durability. Key considerations include:

• Pawl and ratchet ring metallurgy – Stronger metals like chromoly resist wear better under high impact.
• Lubrication – Thick grease cushions the pawl blow but reduces sound. Thin oil amplifies noise but can increase wear.
• Pawl and spring tension – Stiffer springs generate louder clicks but also more stress on parts.
• Number of pawls – More pawls increase sound but also potential for jamming.
• Ratchet ring tooth profile – Shape, size, and spacing affect click volume and durability.

So while loud hubs are expected for BMX, designers still aim for optimal acoustics and performance.

The Appeal of Loud Hubs

There are reasons beyond pure engineering why BMX hubs evolved to be so noisy:

Rider Experience

• The loud clicks create engaging audible feedback for riders.
• It gives a satisfying freewheeling soundtrack to bike handling.

Bike Control

• The noise provides cadence feedback to gauge coasting speed.
• It helps riders time maneuvers like barspins or tailwhips.

Style and Expression

• The unique buzzing sound has become part of BMX culture and identity.
• Custom colored anodized hubs have become a way to personalize a bike’s look and sound.

Are Loud Hubs Necessary?

With the reasons behind noisy BMX hubs covered, some may wonder – are they really necessary? Couldn’t hubs be designed to be quieter?

The simple answer is loud hubs are not required. But the buzzing and clicking has become so ingrained in BMX culture that most riders expect and desire that signature noise. Silent hubs on BMX bikes would seem oddly quiet.

However, there is also appeal for BMX hubs designed for stealth. Some street riders prefer stealth hubs when riding spots where noise can attract security.

So while loud hubs are absolutely not mandatory, they’ve become standard because most BMX riders ultimately want that unique sound. It’s part of the BMX experience.

Maintaining and Modifying Noisy BMX Hubs

To keep BMX hubs running smoothly and sounding crisp:

• Disassemble and clean the hub internals periodically. Remove built-up grease and grime.
• Lubricate with quality waterproof grease or oil made for freehubs.
• Check the pawl springs for any cracks or loss of tension. Replace if weakened.
• Examine ratchet ring and pawls for wear, damage, or deformation. Replace if excessively worn.
• Swap in stronger pawl springs to increase click volume. Or use quieter springs to reduce noise.
• For max sound, upgrade to a hub with more pawls like a Profile Racing or Cinema hub.

With proper maintenance and modifications, a loud BMX hub’s unique sound can continue for many miles.

In Summary

In summary, there are several key engineering differences that make BMX hubs so much louder than standard bicycle hubs:

• More pawls engaging at once
• Pawl overlap creates simultaneous clicks
• Aluminum or titanium pawls
• Stronger pawl springs
• Wider ratchet ring design
• Positioning maximizes sound resonance

These design factors generate the loud, rapidly repeating buzzing and clicking noise that BMX riders love. While not mandatory, the sound has become integral to the BMX riding experience and culture.

So the next time you hear a rider coasting down the street with their hub rattling away, you’ll know the engineering considerations behind creating those clicks!

FAQs

Why do some BMX hubs click louder than others?

More expensive, high-end BMX hubs from brands like Profile Racing use design optimizations like more pawls, stronger springs, and better metallurgy to maximize click volume. Cheaper hubs often have fewer pawls and lower tolerances resulting in less noise.

What hub sounds the loudest?

Currently, the Profile Elite hub is considered one of the loudest hubs money can buy. Some of the loudest hubs use titanium or magnesium pawls instead of steel for maximum click volume.

Do louder hubs mean more quality/performance?

Not necessarily – loudness does not directly equate to hub quality. Noisy hubs put more stress on components which can decrease longevity if not engineered properly. High performing hubs aim for an optimal balance of noise and durability.