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In case you are shopping for a brand new wheelset, you may encounter two hub flange designs: closed and open. There are horror tales surrounding the open hub flange design, as it may possibly result in full lack of spoke retention, doubtlessly inflicting a sudden, catastrophic wheel collapse in a crash or onerous impression.
On this article, I’ll stroll you thru how each methods work, the place open flanges make sense (particularly with carbon spokes), and while you’re higher off selecting a safer, closed or “captured” design.
KEY TAKEAWAY
Open hub flanges are widespread on wheels with carbon spokes and might provide weight and manufacturing benefits. Nevertheless, they rely closely on spoke stress and, with no correct seize system, might not retain spokes nicely in excessive conditions.
Closed flanges (or open designs with an efficient spoke-capture answer) add a little bit of weight however present higher structural integrity and maintain spokes in place even after injury. For many riders, they’re the safer and extra sturdy selection. That’s one motive why many producers, particularly Chinese language manufacturers, are shifting away from absolutely open flanges towards closed or semi-captured designs.
What Hub Flanges Do
Hub flanges are the components of the hub the place the spokes connect. They switch load between the hub and the rim and considerably have an effect on wheel power and stability.
Closed or enclosed flanges, with out massive cutouts, are normally heavier. In return, they provide higher structural integrity and scale back stress concentrations across the spoke interface.
As a result of the flange helps the spoke head or threaded finish, its design additionally impacts long-term sturdiness and the wheel’s habits after spoke injury or failure.
Open (Cutout) Flange Hubs
Open, or cutout, flanges have home windows or slots that expose the spoke heads or ends as a substitute of absolutely enclosing them.
On some designs, particularly older steel-spoke methods, an open flange mixed with easy J-bend or large-head spokes can enable a spoke to be ejected if stress is all of a sudden misplaced, reminiscent of after a crash.
In open flange hubs, if a number of spokes fail and opposing stress disappears, the remaining spokes can rotate or “spin out” of the hub shell. There isn’t any mechanical cease to maintain them in place. This may result in full lack of spoke retention and fast wheel collapse.
Wheels with open or cutout flanges that lack any seize system rely totally on spoke stress and flange geometry to maintain spokes seated. In uncommon however extreme occasions, onerous pothole impacts, bike-to-bike contact, or crashes, a number of spokes can detach without delay.
This failure mode is unusual in on a regular basis using, however it’s actual. It has led to remembers and design modifications prior to now, significantly on high-end aero wheels.
Open Flanges and Carbon Spokes
Fashionable carbon street wheels are the place open flange points are most related. Carbon spokes are normally broad, making them unimaginable to insert by way of small, absolutely closed holes.
The draw back is that, in lots of of those designs, there is no such thing as a true mechanical seize if stress is misplaced. This downside largely impacts carbon-spoke wheels. Metal-spoke hub producers realized way back that absolutely open flanges with out retention might be problematic and largely deserted them.
On open-flange carbon hubs, dropping a number of spokes in a crash can enable the remaining spokes to sequentially eject from the hub because the wheel deforms and rotates.
Open Flange Options that May Work
Nepest makes use of a patented open-hub flange design on its NOVA wheels that goals to deal with a number of the conventional weaknesses of open flanges. As an alternative of relying purely on spoke stress, Nepest’s system shapes the flange home windows and spoke interfaces so the spoke heads are partially captured throughout the hub shell. Regardless that the flange is visually open, the spokes sit deeper and are guided by the flange geometry, serving to stop them from freely ejecting when stress drops.
This method retains the burden and meeting benefits of an open flange, whereas bettering spoke retention in comparison with absolutely open, window-only designs.
That stated, it’s nonetheless basically an open flange system. In excessive crash eventualities, it can not provide the identical degree of mechanical safety as a completely closed or threaded seize design. It’s greatest considered as a safer evolution of the open-flange idea reasonably than a full substitute for closed flanges.
TIP: Based mostly on my dialogue with Patrick Clark, co-founder of the wheel model Particle, who has deep insider data of Chinese language wheel factories, it’s sensible to remain considerably skeptical of patent and aerodynamic claims or impression take a look at outcomes, particularly once they come from Chinese language manufacturers.
Closed (Enclosed) Flange Designs
Closed-flange designs maintain the spoke head or threaded finish absolutely enclosed by materials. Even when spoke stress drops, the spoke can not merely fall out. In some trendy methods, spokes even screws into the hub flange utilizing a threaded insert. The threads act as a constructive seize mechanism, protecting the spoke seated even when it’s minimize or loses stress.
Nevertheless, this method might be susceptible to spoke twisting, lack of stress, and getting out of essentially the most aerodynamic orientation.
Closed flanges are normally heavier as a result of they use extra materials. Nevertheless, they distribute the load extra evenly and keep away from sharp stress factors which can be widespread in open-flange designs (see the picture beneath).
Within the following demonstration, wheel builder and Caden Wheels founder Ben Cawood cuts two carbon spokes on a entrance wheel after which rides uphill out of the saddle at round 95 kg physique weight. Regardless of the lacking spokes, the remaining spokes keep within the hub, and the wheel stays rideable.
This exhibits the important thing security benefit of closed or captured flange methods: the wheel can deform and lose native stress with out instantly ejecting spokes from the hub.
Conclusion
Open flanges with carbon spokes had been initially fashionable as a result of they made lacing and spoke substitute simpler. They had been additionally lighter and appeared higher on a spec sheet.
Nevertheless, a number of well-known Chinese language manufacturers, together with Winspace (Lún) and Elitewheels, have moved away from open-flange designs used of their early generations. Full wheel failures are uncommon, however I feel this shift is an efficient factor.
On the subject of wheels, I’ll fortunately settle for a number of further grams in trade for higher spoke retention and a decrease threat of catastrophic failure. I’m additionally glad that the producers listened to suggestions from reviewers like Peak Torque and adjusted their designs accordingly.
I additionally up to date my previous wheel opinions to incorporate this data. I clearly level out which flanges every wheelset makes use of so you can also make a extra knowledgeable determination.
In case you are out there for a brand new wheelset, I like to recommend testing my in-depth information on how to decide on street bike wheels.
