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Gemini Forges Rigel Carbon MTB Chainrings, the World’s Lightest at 39g Make You Faster!

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, backside
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Gemini calls their new Rigel carbon ring the “most technologically advanced chainring” to ever be made. And says it is “truly the lightest chainring in the world.” Crafted from continuous fiber ‘forged’ carbon over an aluminum skeleton, the narrow-wide 1x Gemini Rigel carbon chainrings are stiff, long-wearing, even aero, plus of course incredibly lightweight.

Gemini Rigel carbon 1x MTB chainrings

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings
(Photos/Gemini)

We’ve seen a number of carbon and composite chainrings over the years. I even made a full carbon chainring for my singlespeed mountain bike more than 2 decades ago that seriously outlasted alloy rings. Carbon lightness and stiffness have been promising in the chainring department. But none have really solved the issues of creating sharp & complex teeth from carbon that can handle varying chain angles, aid chain retention, and survive regular wear and tear. The most successful until now have resorted to making the outer ring of teeth out of various metals. And limiting the carbon to structural reinforcement or a lighter spider design.

Until now…

Gemini Rigel forged carbon ultralight 1x MTB chainring, tooth detail rendering

Gemini crafts the Rigel direct mount chainrings mostly from carbon, but with alloy at the chain’s contact surface with the chainring’s teeth.

Who is Gemini again?

Gemini Rigel forged carbon ultralight 1x MTB chainring

We mostly know Gemini Composites for their premium carbon mountain bike bars and 1-piece cockpits. Started in 2015 to develop advanced carbon MTB components by Roland Baides, a bike design engineer out of the Cero design studio. Baides became the chief design engineer for Unno for the first 2 years of the new mountain bike brand, before returning full-time to Gemini.

Now, situated in a small industrial zone a 1/2 hour up the coast from Barcelona – on top of auto repair & paint shops – Gemini combines their design and carbon production in a single combined studio and workshop. Everything from idea to components, made in-house.

How is Forged Carbon made?

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, inner aluminum teeth

Gemini’s secret sauce is multi-part construction, dubbed ‘Forged Carbon’, aka compression molding. First, a continuous aluminum ring of hollowed-out 7075-T6 alloy is cut. Then, they sandwich the toothed ring between precision-cut prepreg carbon discs, pressed inside a mold, and heated, under more than 100 tons of force to arrive at the final shaping.

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, patent illustrations

The real secret is not entirely revealed – but is patented. The detail of how Gemini orients the fibers in the teeth. Based on our understanding of the patent, the pressure of molding squeezes the unaligned fibers (Discontinuous Fiber Composites similar to what we know as UD) in the precut carbon discs. This aligns the fibers concentrically (3 in Fig. 8-B), as they squeeze into the narrow channels of the teeth in the mold.

Gemini says the result is “an organization of continuous fiber structure in the tooth that is unattainable with traditional carbon fiber manufacturing processes“.

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, hand finishing

Out of the compression mold, there’s still plenty of hand finishing to clean up excess resin flash squeezed out. And to polish the finished Rigel ring.

Tech details

Gemini Rigel forged carbon ultralight 1x MTB chainring, details

According to Gemini, the resulting Rigel is the lightest Direct Mount chainring available. They claim a weight of just 39g for a 30T SRAM 3-bolt ring. “This is primarily thanks to the use of carbon fiber for both the structure and the teeth, despite having an internal metal core dedicated solely to extending its lifespan.”

Gemini Rigel forged carbon ultralight 1x MTB chainring, inner 7075 aluminum Anti-Wear Metal Core

The Rigel rings ultimately expose the edges of the inner alloy ring. That provides direct chain roller to aluminum contact, to transfer pedaling loads through the carbon body.

Gemini Rigel forged carbon ultralight 1x MTB chainring, angled

This means long-term durability against wear. At the same time, the carbon sandwich reduces friction, quiets the chain, and improves the overall aerodynamics of the system.

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, prototype with alloy teeth exposed
Note: This is a prototype chainring where Gemini exposed the inner alloy-toothed ring to illustrate its construction.

Gemini doesn’t explicitly state how many miles or kilometers you can expect to get out of their new carbon Rigel chainrings. But does advise cleaning & maintaining it like a regular ring – preferably using a dry chain lube. They also claim that real conditions durability is effectively similar to conventional aluminum chainrings.

All are manufactured in Barcelona, Spain right where they were designed and engineered.

Gemini Rigel carbon chainrings – Pricing, Options & Compatibility

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, rendering on crankset

The new carbon Gemini Rigel chainrings seem surprisingly affordable actually. OK, at 125€ a piece, they aren’t cheap.

But plenty of machined alloy direct mount chainrings already sell for 70-90€. This is officially cheaper than a stock SRAM XX SL replacement chainring. Even a heavier, non-DM Carbon-Ti 1x chainring made from a similar material mix will set you back 181€.

Gemini limits options to just three tooth sizes for the time being, each with Boost standard 3mm offset: 32, 34, or 36T. If you think you are faster than that, you’ll have to wait until Gemini develops bigger rings…

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings, future sizes

Gemini has been coy with the details, but suggested gravel-ready 38, 40, 42 & 44T rings will come “Soon“, as will a 52/36T pair. And they are also thinking of oval rings, and a version for SRAM’s latest thread-on ring-around-a-powermeter.

Gemini Rigel ultralight compression molded forged carbon 1x direct mount bike chainrings

Compatibility is wide, though. Gemini makes the carbon Rigel chainrings in 5 direct mount interface standards – SRAM 3-bolt, SRAM 8-bolt, Shimano, RaceFace/Easton & Cannondale Hollowgram. That covers the vast majority of direct-mount MTB crank arms out there today. They are said to work with 11 & 12-speed drivetrains from Shimano & SRAM, including T-Type Flattop chains.

Get them now, direct from Gemini.

rideGemini.com

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33 Comments
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Klaster_1
Klaster_1
6 months ago

Any plans for 5-arm 110BCD? I’d consider a 36 for my road bike.

Larry Falk
Larry Falk
6 months ago

Would be interesting to see steel used for the insert as a longer-wearing version.

Greg
Greg
6 months ago
Reply to  Larry Falk

Or titanium, as it’s very friendly to being bonded to carbon.

Veganpotter
Veganpotter
6 months ago
Reply to  Greg

I’d rather have a design that holds better with steel. Titanium teeth wear well and it’s not worth the cost over aluminum.

Drew Diller
6 months ago
Reply to  Veganpotter

I think Greg means that titanium has low galvanic potential compared to carbon, whereas with steel there is greater potential for the steel simply being in contact with the carbon and has far greater potential to spontaneously delaminate

Mike
Mike
6 months ago

Garbaruk makes 48-51g DM 30T chainrings for 2,5x less the price.

E a
E a
6 months ago
Reply to  Mike

AbsoluteBlack as well, competitive on weight and much less price.

Veganpotter
Veganpotter
6 months ago
Reply to  Mike

You always have diminishing returns with every dollar spent. That’s totally normal.

blablabla
blablabla
6 months ago
Reply to  Veganpotter

Yes, but it’s different when You buy eg. a carbon bar, or a seatpost, that will serve You for years, and a carbon chainring that in 1-2 years will become garbage.

Eggs Benedict
Eggs Benedict
6 months ago
Reply to  blablabla

For someone who rides regularly, I doubt these rings would last beyond 3 to 4 months of riding.

Alex
Alex
6 months ago
Reply to  Eggs Benedict

Simple…don’t buy them.

Eggs Benedict
Eggs Benedict
6 months ago
Reply to  Alex

Yes, very simple.

Joe Bond
Joe Bond
6 months ago

Is friction reduction happening through the carbon sandwich acting as a source of powdered graphite?

Greg
Greg
6 months ago
Reply to  Joe Bond

Furthering that, it would be interesting to see some friction reducing particles added, such as tungsten disulphide, or better yet just graphene.

Al_nyc
Al_nyc
6 months ago
Reply to  Joe Bond

There is not much friction there to reduce. The moving parts are in the chain itself.

Hamjam
Hamjam
6 months ago

Hurry, this spice must flow to Dangerholm.

Oliver
Oliver
6 months ago

Forged Carbon is marketing guff. It’s thermoplastic molding. Also their site is down.

Veganpotter
Veganpotter
6 months ago
Reply to  Oliver

Molding doesn’t typically have very high pressures. They may be lying about the pressures but if they’re not, there’s really nothing wrong with calling this forged. And it’s definitely not thermoplastic

Ves
Ves
6 months ago
Reply to  Veganpotter

The Question is – 100T press? What that is? Pressure on what space?
…..on top of auto repair & paint shops – Gemini combines their design and carbon production….
100T press is above , ughm, something……fukit, man.

Chunk
Chunk
6 months ago
Reply to  Ves

Hydraulic presses don’t press against the ground; they squeeze things between a fixed and a movable part. The 100 ton refers to clamping force and has nothing to do with weight. You don’t get heavier or lighter when you squeeze a pair of pliers; presses don’t get heavier when they press things.

Ves
Ves
6 months ago
Reply to  Oliver

https://en.wikipedia.org/wiki/Forging it is hammering the piece. Nobody hammer CFRP. So, yes, you are right, sayng Forged Carbon is BS

Chunk
Chunk
6 months ago
Reply to  Ves

You’re wrong, though. Press forging, which is mentioned right in the article to which you linked, “works by slowly applying a continuous pressure or force, which differs from the near-instantaneous impact of drop-hammer forging. The amount of time the dies are in contact with the workpiece is measured in seconds (as compared to the milliseconds of drop-hammer forges). The press forging operation can be done either cold or hot.”

Maurice Quarles
Maurice Quarles
6 months ago

What about 25t-30t for BMX’ers?

blahblahblah
blahblahblah
6 months ago

but you forgot “and improves the overall aerodynamics of the system”

Deputy Dawg
Deputy Dawg
6 months ago

30t please!

Doc Sarvis
Doc Sarvis
6 months ago

Seems like once a year another snake needs oiling.

Dockboy
Dockboy
6 months ago

Gemini like the astrological sign or Gemini like the space program?

mud
mud
6 months ago

This is insane. How much weight is being saved over alloy? And for a part frequently bashed against logs and rocks!

RobRidesBikes
RobRidesBikes
6 months ago

Wait, so they give the weight for a 30T, but then don’t offer a 30T?

David Bean
David Bean
6 months ago

If it’s patented, it’s not “secret”. It’s public. Gemini may well have trade secrets but those have nothing to do with patents.

Evan
Evan
6 months ago
Reply to  David Bean

It is a secret to the illiterate.

Erik
Erik
5 months ago

AVOID!! Just received a 36T, for SRAM and all 8 bolt holes shattered on installation, before bolts were even snug. You could hear them cracking, as soon as the bolts made contact with the paper thin “carbon”. Do not waste your money!

Pete
Pete
5 months ago
Reply to  Erik

Pic would help to shock us.

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