Condensed answer: BMX hubs are some of the loudest out there because they have the greatest number of engagement points on average.
Why Do BMX Hubs Produce a Clicking Noise?
The hub of a BMX bike has one main function – to cut the connection between the wheel and the cranks when the rider is not pedaling and to resume it once pedaling is restarted.
Here’s how that happens:
The hub has a ratchet mechanism consisting of:
- A ratchet/engagement ring
- Driver + Pawls
When a cyclist is pedaling forward, the pawls on the driver spring out and bite against the teeth of the ratchet ring.
In consequence, the driver’s body and the rest of the hub become one, and the pedaling effort is transmitted to the wheel.
During backpedaling, the cyclist is moving the driver and consequently the pawls backward.
When a pawl reaches a tooth of the ratchet mechanism, the spring is compressed, and the pawl momentarily returns to its “bed”.
When the cyclist stops pedaling. The drive body and consequently the cog or the cassette stop spinning as well.
The ratchet ring and the rest of the hub continue to spin, however. When a tooth of the ratchet ring comes in contact with a pawl, it presses the pawl down. Once the tooth is away from the pawl, the pawl opens once again.
The contact between the pawls and the ratchet ring’s teeth during coasting as well as the spring action of the pawls is behind the sound of the hub.
The difference between backpedaling and coasting is:
1. During coasting the ratchet ring is spinning and touching the pawls.
2. During stationary backpedaling, the driver and consequently the pawls are moving and spinning against the teeth/engagement points.
3. During simultaneous backpedaling and coasting, the ratchet ring and the pawls are moving in the opposite direction and brushing against each other.
Note: Some BMX hubs are built differently. Sometimes the ratchet ring is on the driver whereas the pawls are connected to the hub’s insides. In that case, the principle of operation is similar, although reversed.
What Factors Make a Hub Louder?
1. Engagement points
More teeth on the ratchet ring result in more points of contact and consequently friction against the pawls.
The main motivation to add extra engagement points to a ratchet ring isn’t sound but performance.
A high number of engagement points creates quicker, practically instant, biting of the driver against the ratchet.
The benefit is a faster response upon resuming pedaling. Hence why hub manufacturers increase the number of ratchet teeth on their more expensive hubs.
2. More Pawls
A ratchet ring with a maximum number of teeth means nothing when the number of pawls is low.
To keep the responsiveness of the hub high, producers add extra pawls with strong springs pushing the pawls out with greater force.
More pawls + More Engagement Points = Zero Dead Spots + Lots of Noise
How Many Engagement Points Do BMX Hubs Have?
Below you will find a table containing high-end BMX hubs and their points of engagement (PoE).
|Model||Pawls||Points of Engagement|
|Profile Elite Hub||6||204|
|Promax Pro Cassette Hubset||non-specified||120|
|Tall Order Drone||non-specified||150|
|Supercross Quick Twitch Cassette||3 + 34 micro teeth||120|
|TNT Rapid Fire Cassette||non-specified||150|
|Forward Joyride V2||6||150|
In the next table, you see the engagement points of popular MTB hubs:
|Model||Points of Engagement|
|Hope Pro2 Evo||24|
|DT Swiss DT350||18|
|Hope Pro 4||44|
|Chris King ISO||72|
|Shimano Saint M820||44|
|White Industries XMR||48|
BMX hubs have the greatest number of engagement points.
This explains why BMX hubs produce a distinctive continuous buzzing.
It’s impossible to recreate that sound with an entry-level MTB hub which has 15-16 points of engagement.
The Points of Engagement Aren’t Everything
More points of engagement do not necessarily equal a louder hub. The final sound of the hub depends on the entire system.
For example, the MTB Project 321 hubs have 216 points of engagement and come in two versions. One of them is as loud as expected while the other is silent. The number of engagement points is identical in both cases.
One cannot conclude that a hub is louder than another by looking solely at the number of teeth on the ratchet ring. The entire build has to be taken into consideration.
Loud Hubs Are Part Of BMX Culture
Manufacturers wouldn’t be making loud hubs if the majority of the riders didn’t like them. After all, the customer is always right.
Of course, some find the noise irritating, especially when riding in groups, but the sound has proven to be too iconic to mute.
Here’s a short personal story. A few years back, when I was on the verge of resurrecting my love for cycling, I sat on a staircase near a park. I heard the buzzing of a bike behind me and instantly said to myself – “That’s a BMX.”
One morning, I experienced a similar moment during my bike commute. I was cycling to work when I suddenly heard a hub sound from the other side of the street and knew that it was a BMX without even looking.
Ultimately, it doesn’t matter whether you or I don’t like the buzzing. It’s here to stay because it’s part of the culture.
What’s The Loudest BMX Hubs On The Market?
Profile Elite’s hub with its 204 engagement points seems to be loudest BMX hub out there. The videos don’t do it justice. When you hear it close to you, you will have a feeling that the bike is going downhill even if the rider is coasting casually.
How can I count the engagement points on my hub?
Two ways. You can very slowly spin the driver’s body backward and count each click or disassemble the hub and analyze the ratchet ring.
Why are expensive hubs so much louder than the cheap models?
I have a detailed post dedicated to this very subject. You can read it here.
Are There Downsides To Having a Hub With Lots of Engagement Points?
Actually, yes. The quick engagement is greatly appreciated when rolling forward, but it could create problems for the rider in the fakie position.
When you land a trick that requires you to ride backward, the lag that slow biting hubs have is beneficial because you have more time to recover.
In consequence, racing BMX hubs tend to have more points of engagement as those bikes have less to lose from the aforementioned downside.
What Are The Advantages of a Loud BMX Hub?
A loud hub has the following benefits:
1. Quicker engagement.
2. Distinctive “gangsta” sound alarming those around you who’s boss.
Some people claim that the sound of the hub helps them concentrate due to its calming and hypnotizing effect.
What Are The Disadvantages of a Loud BMX Hub?
1. Annoyance (not everybody likes a bike that sounds like a motorcycle when moving at 3 km/h)
2. No “Stealth Mode”
When you have a loud hub, it’s hard to pass by people unnoticed. This could be a problem if you’re riding in a residential area during quiet hours.
3. Unnecessary quick engagement
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