MFU Driver Technology

Onyx has been a pioneer in hub technology for years. The patented sprag clutch mechanism offers ride characteristics, performance, and robustness no other mechanism can. On top of that and nearly limitless colour options, Onyx hubs have arguably the best freehub/driver mechanism around. 

Read further to learn why that is! 

High Level of Modularity

Since 2020 Onyx has supplied all their Classic and Vesper hubs with MFU assembly. The three-letter acronym stands for modular freehub unit. It’s a brilliant piece of engineering since it creates a level of modularity across the whole product lineup that isn’t seen anywhere else!

All the Classic and Vesper hubs employ the same freehub body – or the driver as it’s called. Thanks to the clever engineering done at Onyx HQ, one can use the same freehub body for Classic hubs equipped with downhill-specific 110x20mm / 157x12mm sizing and Vesper hubs that would be suited to gravel duties in 100x12mm / 142x12mm specification.

Installation is as simple as it can be. The driver employs a press fit style of assembly and is held in place by the end cap/widget. Simply pull the end cap off and perform the same manoeuvre with the driver. Installing the driver is done the same way but in the opposite manner. 

No Need for Else

The true beauty of the MFU axle design manifests itself when the need arises the move on from one freehub interface standard to another, say from Sram XDR to Shimano Micro Spline or the other way around. The only part that needs replacing is the driver itself – and in some cases the end cap. No need to replace axles and bearings with them and perform a full teardown of the hub in the process.

The Shimano HG, and Sram XDR drivers share the same end cap/widget whilst the Shimano MS driver has a dedicated one. In the latter case, the end cap is clearly marked with the text “Micro Spline”. 

If the need arises to replace the end cap with the driver, it’s best to make sure that it’s of the correct model. End caps for 12mm thru-axles are supplied in two versions: regular and +3.5mm version. The end cap model depends on the axle sizing. Refer to the schematic table below.

End Cap ModelStandard version+3.5mm version
MTB, road and gravel135mm142mm
MTB141mm (“Boost QR”)148mm Boost
MTB150mm157mm Super Boost
MTB & Fatbike170mm177mm
Fatbike190mm197mm

It comes quickly apparent that the +3.5mm end caps add 7mm to the axle length.



Do note that exceptions might present themselves in certain cases. For example, the end caps might differ between the Centerlock and the ISO 6-bolt shells. If in doubt, ensure that you are about to order the correct one.

XD vs XDR

Since the introduction of the MFU axle design, Onyx Racing Products hubs only been supplied with the Sram XDR driver. This has been a source of confusion from time to time since the majority of mountain bike cassettes employ the XD standard.

Conveniently, the XDR can be converted to XD with the use of a 1.85mm thick spacer that’s supplied with all XDR-equipped hubs.

In Summary

MFU axle design is an expression of clever engineering that brings several benefits. Among them are a highly functional and robust design. The modular design makes all drivers cross-compatible with each other which makes the move from one interface to the next a breeze. 

Disassembly and installation require no tools – a feature that makes the MFU a truly universal design. 

Older hubs can be upgraded to the current MFU axle design. The list of needed parts includes the driver, axle, end caps/widgets and the lockring.  

Weight Matters – But How Much Exactly?

The cycling industry has a long and complicated relationship with weight. The traditional line of thinking has been that the less there is of it, the better. Often time this is the case, but the scale of effect the weight savings have differs quite a bit of the assumed one.

Read further to learn what science says, and how it relates to hubs.

First Things First

To lay the foundation for this subject, some groundwork needs to be laid. How weight affects the handling of the bike, and how much is it location-dependent? In other words, how much does it matter if the additional mass is located around the bottom bracket, saddle, outer circumference of a wheel or in a hub – if it does at all? 

In general, the rotational mass has a bigger effect on the handling of the bike than mass that is stationary or put in other words, non-rotating. In practical terms, this means that the mass located on the wheels have a bigger effect on handling than other components found on the bike. Yes, the drivetrain components such as cranks, chainrings and pedals do rotate, but their effect is negligible at best because of the short radius on low rotational speeds.  

Secondly, it’s important to recognize the situations where the effects of the additional mass are the biggest. This can be summarized into two scenarios:

1) Acceleration. This is where the speed of the rotating component sees a change. The bigger the mass that needs to spin faster, the bigger the required energy.

2) Climbing. This is a game against gravity that cannot be cheated in. Every gram that the rider-bicycle-unit has, needs to be “lifted” up when climbing. The rise in potential energy requires more kinetic energy which in turn is supplied by the rider. 

What does Science say?

Pinkbike – the leading mountain bike site – published a very well-written article about weight and how much riders should worry about it. To give credit where its due, the author Seb Stott did an excellent job in writing the article as well as laying out the related equation.

Because wheels roll, they have a fixed relationship between their translational speed and their rotational speed, and this gives them a fixed relationship between the rotational and translational kinetic energy. The vast majority of the rotational kinetic energy in a bicycle wheel comes from the mass at the outer edge (the rim and tire) – the hub and spokes are pretty negligible.

-Seb Stott

If you want to read the full story and see how the math plays out work, head to the following link. 

Pinkbike.com – Why You Should Not Worry About Weight Much

A very nice graphical illustration of this was posted by our friends at the.european.bike.project Instagram channel. Both wheels have the same amount of mass in the video, but the faster one has the weight placed on the inner circumference. Quite a noticeable effect one could say.

Wheat from the Chaff 

To get a handle on things that truly matter and play a noticeable effect on performance and ride quality, the following points should be taken into account.

  • Always consider the amount of mass in question in relation to the whole rider-bicycle-system. A weight saving of 250g might sound considerable, but in a system of 90kg for example (70kg rider, 5kg gear, 15kg bike) it represents only 0,27 % of the whole. 
  • The mass that is located on the outer circumference of rotating parts has the most notable effect. In practical terms we are speaking of tires, rims and possibly inserts here.
  • Every gram counts in climbing, but it is still best to keep the big picture in mind. Does a weight saving of, let’s say 50g, give a noticeable performance benefit? And is it worth the potential compromise in component performance, durability or otherwise?

It’s About Priorities 

Onyx Racing Products hubs aren’t the lightest ones out there – which is a well-known fact. From the start, the design behind the hubs was to create a hub with the highest performance possible with features that are unparalleled in the industry. The patented sprag clutch mechanism, carefully dimensioned hybrid ceramic bearings and overall robust hub construction fulfil this criterion. 

Some of the benefits Onyx Racing Products hubs are known for include:

  • Instant engagement.
  • Low-drag and very low friction – which is backed by independent 3rd party lab measurements.
  • Fully silent operation.
  • Low-service needs and highly reliable function.

All of these features require a robust structure. Considerable forces take place within the patented sprag clutch mechanism. To withstand this the sprags themselves are made of hardened steel which is paired with a sleeve made of similar material inside the rear hub shell. Lesser material wouldn’t simply do in highly demanding applications like this. 

All of this means that the Onyx Racing Products hubs aren’t the lightest ones out there – which can be considered a downside in an industry that has been weight-obsessed for more than half a century. Luckily, in the light of physics, the effect of added mass has a very negative little effect – especially in demanding and gravity-orientated applications. 

Onyx Racing Product hubs remain the premiere and winning choice in all riding disciplines, even though they are not the lightest ones around. Performance and functionality over grams.

Explore the Onyx Racing Products lineup from our shop.

Are Silent Hubs Better?

Bikerumor.com, a news site covering everything biking-related, published an article with a similar title. Some of the most notable brands in the industry offered their views on the matter. Onyx Racing Products was included, naturally.

The full text can be read here: Bikerumor.com – Are Silent Hubs Better?

Going through the text is highly recommended, and functions as a form of education to anyone interested in the inner workings of a bicycle rear hub, and for those, who are chasing the last percentiles of high-performance in the form of minimizing friction, and the drag it causes. 

One might argue that the headline of the article and the question it entails, leads to the wrong direction from the start since it confuses driving features (the things that matter), and the driven features (things that do not matter, but are observable). Sure, articles need to have an interesting title to collect as many views as possible, but this consideration is still worth taking a closer look.

Driving Features

Let’s start off by listing some of the driving features that are also the most important design considerations on a bicycle rear hub. The list includes things like the following:

  • Robust and strong construction
  • Modular structure 
  • Bearing choice and design to minimize friction and to maximize bearing life 
  • Fast engagement
  • Low maintenance, and easy to service
  • Competitive weight

Sound, the level of it or the lack of thereof, aren’t mentioned on the list above – why? Because it’s not of the same level of importance. It’s simply a driven feature, a side-effect one might say. 

Freehub Mechanism 

The inner workings of the freehub system and the exact mechanism it employs dictates what type of sound is produced while coasting. If the design is started off with this basis more important features could be sacrificed, which would be a bad trade-off. 

The Onyx Racing Product hubs are silent thanks to the patented sprag clutch mechanism found on every rear hub produced by Onyx, all the way from the slender OHM junior BMX hub to the robust and time-proven Classic mountain bike hub. 

The sprag clutch mechanism works so that a dense row of sprags is placed between the driver and the hub shell. The sprags are formed so that they allow movement in one direction. When the direction is changed with the application of pedaling force to the chain, the sprags “stand up” 

between the two cylindrical surfaces, creating an instant and very strong engagement. 

If a more detailed explanation is in order, refer to the previously published article: The Differentiating Factor in Onyx Racing Products Hubs.

In order for the system to function, it must be in contact with the rotating cylindrical surfaces 100% of the time. Otherwise, the system would not work. The contact force is very low though, which is the secret behind the speed of the Onyx Racing Products hubs.  

Silence = Low Drag 

Sound requires energy. The buzzing sound of a freehub is taken out of the kinetic energy stores that the combination of the bike, and the rider possesses. The more energy the sound requires to manifest itself, the more drag there is. 

The sprag clutch mechanism found on the Onyx Racing Products hubs does not rob any speed in this way, and they’re measurably the fastest hubs out there. 

Onyx Racing Products Hubs Are the Fastest Out There and It’s Backed Up by Science

And yes, we do admit that besides being fast, silent hubs are also very cool. Stealth mode activated.

Onyx Racing Products Hubs Are the Fastest Out There – and It’s Backed Up by Science!

“I want the fastest wheelset possible”, “Rolling resistance should be avoided like a plague”, “Efficiency needs to be maximized”. If you subscribe to any of these phrases or similar thinking, keep reading to learn why the Onyx Racing Products are the fastest out there – proved by science.

The Friction Elements

When striving to build the fastest wheelset out there, it’s best to take a look what’s causing the friction that is slowing you down, whether it’s on a BMX track, attacking a classic mountain climb, or shredding down a double black diamond trail. 

Rolling resistance caused by tires is one big factor, but we’ll be leaving that out since it has little to do with wheel or hub choice. Therefore, the sources of friction, which will stop the wheels from spinning and slow you down eventually are as follows:

  • Bearing friction
    • Rolling and sliding
    • Lubrication
    • Seal friction
  • Freewheel drag
  • Tolerances, build quality etc.

Bearing Friction

Let’s attack the first element which is bearing friction. It is caused mainly by three sources: the rolling friction inherent to the moving elements found inside the bearing, the choice and type of lubricant used and lastly, the friction caused by the protective components, also known as seals. 

In short, the rolling and sliding friction happens between the bearing balls and the outer and inner races because of the slight deformation happening under load conditions and imperfections in the surfaces and shapes of the components. Even though high-quality bearings have bearing balls with a very high level of roundness, perfection is rarely obtained. 

On a side note, the advantage of ceramic bearings is mostly related to the hardness of the material and the fact that ceramic balls can be made rounder than their steel counterparts. But, that’s a topic for its own discussion, and we’ll leave at that for now.  

The choice of lubricant plays a role as well in how easily the bearings rotate. A general rule of thumb here is that the thicket the lubricant, the more it resists any movement. By the same logic, thinner oils would be the lubricant of choice, if low rolling resistance is pursued, then a thin oil would be a good choice of lubricant. However, the compromise presents itself in low service-life as well as the level of protection provided. 

Thin oils wear out or “disappear” from the bearings or any similar type of assembly fast and easily, thus requiring periodic service. Marine greases are found on the other far end of the spectrum with their goo-like viscosity, and durability. The added advantage is the level of protection those types of lubricants offer against outside contaminants, such as water and moisture. 

Lastly, we got seal friction. The same rule applies here. The more carefully the bearing is enclosed and therefore protected from contaminants, the more friction the seal structure introduces to the system. A variety of seal structures can be found used in bicycle applications. A good primer on the subject with informative photos can be found on Enduro Bearings’s site.

Onyx Racing Hubs use high-quality steel bearings whereas the Classic models employ hybrid ceramic bearings as standard, manufacturer by Verinent Bearings in the USA.

Freewheel Drag

The freewheel or any type of clutch mechanism used in the rear hub introduces some drag to the system as default. Anyone with even a primary level of riding experience has surely encountered at least once a hub that makes a distinct clicking or buzzing sound when coasting. According to the law of energy conservation, the sound can’t come out of thin air. Energy input is needed for its manifestation. The louder the sound, the more energy it requires – usually. All the energy that goes into producing that freewheel sound is in turn “robbed” from the kinetic energy possessed by the bike and the rider. 

The patented sprag clutch mechanism found on Onyx Racing Products hub does not feature any sound – as most of you reading are most likely well aware of. Therefore, at least in theory, there’s a clear advantage on offer. Happily, the low drag nature and the advantage present has been quantified by Duke University in 2016 with their quest in creating the most efficient electric vehicle possible. The research project included measuring the drag found on some of the most highly regarded hub models. 

The results can be seen in the graph below. The higher the bar, the more drag there is. Other than that, not much explaining is required. 

Tolerances and Build Quality

Lastly, there’s the area of build quality and aspects related to it like the design itself, the level of tolerances required to achieve satisfactory function etc. Some examples of potential faults or problems that might occur are too loose or tight bearing seats, parts that are slightly eccentric instead of being fully concentric, and the dimensioning of shoulder parts on axles or sleeves on top of the axles which prevent excessive bearing preload with their presence. 

In short, Onyx Racing Products hold the highest tolerances and manufacturing quality out there, something that even an aerospace component manufacturer would be proud of. When purchasing an Onyx Racing Product hub, you’ll get the most forward-thinking design with a matching quality that translate to superior ride experience.

In Summary

The feeling of speed and low drag found on Onyx Racing Products hubs is more than just a subjective observation. Thanks to the patented sprag clutch mechanism, high-quality bearings, and superior build quality, they are the fastest out there, and it’s backed up by science.  

Get your Onyx Racing Products hubs now.



Onyx Racing Products – Hubs for MTB, BMX, Gravel, Road and Specialty bikes

Onyx Classic vs. Vesper – Which One Should I choose?

Classic vs. the Vesper hub? Which one should I choose?

This is a classic question (pun intended) that we hear on a weekly basis. Therefore it is worth addressing on a more detailed level. By the end of this article, you’ll be armed with more information about the differences between these two hub models, and most importantly – which suits your situation the best!

The Short List

Both hubs are available in nearly all possible axle configurations and sizes, including all the common freewheel driver standards, as well as ISO 6-bolt or Centerlock disc mounts. No differences here then. Both hub models employ the patented sprag clutch mechanism Onyx Racing Products hubs are known for. Besides that, the hub shells of both models are made from aerospace-grade 7075 T6 aluminum which is the strongest aluminum alloy available, and thus widely used in high-demand applications.

Some of the main features of both models are listed below.

Classic

  • The strongest sprag clutch mechanism found on the Onyx Racing Products lineup, excluding the Ultra SS series dedicated for BMX racing bikes.
  • Classic looks – as the name states.
  • Onyx hybrid-ceramic bearings as standard.
  • Symmetrical hub flange diameter on both sides.
  • Choice between standard and Helix hub shell on the front. Latter has weight-saving cut outs which also give a highly technical and detailed appearance.

Vesper

  • Lighter version of the Classic hub. The weight savings are achieved with two main factors: minimalist hub shell size, and smaller sparag clutch.
  • Sprag clutch mechanism is approximately 75% of the size found in the Classic hub.
  • Highly technical and refined looks!
  • Steel bearings as standard. Onyx hybrid-ceramic bearings are available as an upgrade option.
  • Hub flange diameter might differ between sides, thus affecting spoke length.

Lastly, it is worth noting that both hubs are available in the wide array of colors Onyx Racing Products is known for, including several anodized and powder-coated finishes, and the choice for custom-colored widgets and end caps.

The Weight Game

It is worth stating from the gate that Onyx hubs aren’t the lightest ones out there. This is due to several reasons. First, the hubs are made to last and perform flawlessly many, many seasons to come. Second, the sprag clutch mechanism includes by default a hefty amount of hardened high-grade steel which comes with its own weight. Third, Onyx hubs are designed around appropriate bearing sizes which are up for the loads occurring in typical and even extreme situations. It is far more common than generally thought that hubs are built around undersized bearings which come with their own set of problems.

Having said that, here are some actual measured weights for Onyx Racing Product hubs in several configurations.

Classic
Onyx Classic ISO 6-Bolt 110x15mm Front – 221g
Onyx Classic ISO 6-Bolt 148mm Rear XD Driver – 421g
Onyx Classic ISO 6-Bolt 148mm Rear Shimano HG Stainless Steel Driver – 505g

Vesper
Onyx Vesper ISO 6-Bolt 110x15mm Front – 166g
Onyx Vesper Centerlock 110x15mm Front – 144g
Onyx Vesper ISO 6-Bolt 148x12mm Rear Sram XDR Driver – 390g
Onyx Vesper ISO 6-Bolt 148x12mm Rear Shimano HG Driver – 401g
Onyx Vesper Centerlock 148x12mm  Rear Sram XDR Driver – 358g

To see more actual hub weights, refer to the excellent article published at Noblwheels.com. How much does weight matter actually? For this, the splendid article written by Seb Stott is worth looking into.

Pinkbike.com – Nerding Out: Why You Shouldn’t Worry Too Much About Weight

Choose by Application

The choice should be done by personal preference, but most importantly, by application. It is stated at Onyxrp.com:

The Vesper product line is our lightest cross-country and trail hub.  The Classic product line is designed for heavier activities like electric-assist bikes, bike packing, tandems, and bigger riders.

In other words, if you’re heavy and/or especially heavy on bikes, we’d recommend going for the Classic hubs. Having said that, Onyx does offer downhill-specific Vesper hub sets which indicates that despite their lightweight, Vespers can take their share of abuse.

Consequently, if you’re building a lightweight bike for less than extreme use, the Vesper hubs will serve you well.

Some suggestions are listed below based on planned application and riding discipline.

The Vesper hubs are suited for the following use cases and scenarios.

  • XC riding and/or racing
  • Trail riding
  • Enduro riding and/or racing
  • Downhill riding and/or racing (in certain scenarios)
  • Road riding and/or racing
  • Gravel riding and/or racing
  • Commuting

The Classic hubs are the weapon of choice for the following types of riding, use cases, and scenarios.

  • Heavy duty trail riding
  • Enduro riding and/or racing
  • E-MTB use.
  • E-bikes in general.
  • Tandems.
  • Heavier riders with weight approacing or exceeding 100kg.

Here you go. Hopefully, these bits of information make the choice easier so that you are able to pick the right tool for the job – the Classic or Vesper in this case – and enjoy the stealth operation and instant engagement Onyx hubs are known for.

Onyx Racing Products – The Differentiating Factor

The sprag clutch mechanism is the secret behind the awarded instant and silent engagement in Onyx Racing Products hubs. Here you can learn what goes into this technology, and what advantages it brings to the table.

Rooted in Industrial Applications

The sprag clutch mechanism resembles a roller bearing, with the key difference that instead of perfectly round balls, the sprags are shaped like an asymmetrical figure-eight. Another big difference is that the sprags do not rotate, but sit still between two rotating cylindrical surfaces.

When torque is applied to the system and the direction of rotation changes, the sprags wedge themselves between the two cylindrical surfaces and thus creating a very strong coupling based on friction.

See the sprag clutch in action on the photos below. On the left-hand side, the sprags are disengaged, allowing the hub body and the freehub to spin freely in relation to each other. On the right side photo, torque is applied to the freehub body via drivetrain and engagement has taken place.

Sprag clutch mechanism is widely used in industrial and automotive applications, as well as in aviation. If the sprag clutch mechanism is strong and reliable enough to transfer power to the rotor of a helicopter, it’s up for the task to transfer all the power available from one’s legs to the rear wheel.

The Benefits

That’s for the technical jargon.

“What’s in it for me?”

Glad that you asked. The sprag clutch mechanism offers several benefits, all of which can be felt on the trail, road or track. The most notable are listed below:

  • Instant engagement. The sprag clutch mechanism offers instant engagement. In other words, when power is applied to the pedals, and thus torque to the rear hub, the system engages with zero delay! Gone are the days when you have nearly 1/4 of slack of the crank revolution before the rear hub picks up, making your bike feel almost like broken.
  • Smooth pick up. The engagement of the sprag clutch mechanism isn’t binary in nature as in most other system found in the market. Conversely, there’s a wind up effect when the sprags “stand up” between the hub shell, and freehub, creating a softness in the engagement. Many riders feel that this adds grip which is beneficial especially on steep uphills. If this is of concern, and/or you want to learn more, head to our FAQ section.
  • Silent operation. No sound is produced when the sprag clutch operates. In other words, you can ride in full stealth mode, and enjoy the sounds of the environment.
  • Low-drag. Compared to other freewheel mechanisms, the sprag clutch system is one of the most, if not the most low-friction option out there. The sprags are in very light contact with the rotating surface, otherwise engagement would not happen when torque is applied, but the drag caused is among the lowest, if not the lowest among all hubs. Want to have hubs that spin silently and nearly indefinitelty? Choose Onyx Racing Products.
  • Low-maintence. The sprag clutch mechanism or any other component of the Onyx Racing Products hub is not subjected to high wear rate, or do not use components like springs, that are subjected to wear or fatigue, and thus require frequent maintenance.
The double row sprag clutch mechanism found inside the Vesper rear hub.

Video Instead?

Do you prefer video format instead? Then watch this excellent video made by Onyx Racing Products.

Photo credit: Onyx Racing Products