This Carbon Chainring Weighs Just 39 grams

Dec 15, 2023 at 4:16
by Seb Stott  
photo

A carbon-fibre MTB chainring may sound about as durable as a chocolate teapot, but a Barcelona-based company called Gemini claim to have come up with some clever tech to make it work. They say they've put in more than 3 years of research and development, 500 prototypes, and thousands of kilometres of testing, resulting in two international patent applications and what they call "the most technologically advanced chainring on the market."

First, let's talk about why you'd want a carbon chainring. The claimed weight is just 39 grams (30 teeth). That compares to about 59 g for a 30T SRAM direct mount ring (one of the lightest made from aluminium); so we're talking about a 20-gram saving, which will only be worth considering to the biggest weight weenies and/or professional XC athletes. The press release also claims that it's more aerodynamic and reduces friction with the chain, but that sounds like an even more marginal gain. It goes on to say that the chainring offers an "unparalleled sense of finesse during pedalling." Super.

photo
The wear-resistant aluminium core is set inside the carbon teeth.
photo
The inside edges of the teeth are faced with aluminium.

More interesting to me is how Gemini have managed to make a carbon chainring which they say has "unmatched durability for a carbon chainring". On their website, it even says that "wear will be similar to that of an aluminium chainring."

The Gemini Rigel chainring uses a 7075 T6 Aluminum core, which is sandwiched inside the carbon teeth. Gemini then uses something called forged carbon, which involves pressing the fibres together with more than 100 tons of force. Gemini say "the fibers of the composite are arranged through the geometry of the chainring wrapping the metal core while providing a continuous structural organization along the tooth that provides high stiffness levels impossible to achieve with any other carbon chainring manufacturing process".

It's designed to be compatible with any 11 or 12 speed chain on the market, including Shimano, SRAM Eagle, and SRAM Eagle Flattop chains. It's available with 32, 34 & 36 teeth (30 and 38 coming soon), with a standard 3 mm offset (Boost). It only comes as a direct mount and round shape for now, but Oval and 104 BCD should be available soon. The supported crank interfaces are: SRAM 3 bolt, SRAM 8 bolt, Shimano, RaceFace/Easton, Cannondale Hollowgram.

The price? 125€

ridegemini.com




Author Info:
seb-stott avatar

Member since Dec 29, 2014
298 articles

142 Comments
  • 148 3
 Waiting for the e-bike version to match with my e-wings and just get fully overwhelmed by all the weight savings.
  • 42 0
 I am thoroughly whelmed!
  • 17 15
 @justincs: Very clever, but I'm 'a keep on using my Sram steel chainring, going strong after 6 years with no wear to speak of! I'd rather pay the weight penalty on a ring that lasts 6 years and cost me £15 than even pay for an alloy ring every 2 years at twice that price, let alone one that only lasts as long as an alloy ring and costs 8.3 times more than my steelie lol
  • 6 0
 Those grams saved on your ebike will make you charge the climbs. KOMs are coming your way.
  • 3 9
flag zepper (Dec 15, 2023 at 20:10) (Below Threshold)
 @bunjiman82: I just threw away a perfectly good SRAM steel chainring that came with a crankset i bought. I thought no one would ever be stupid enough to actually buy this. I coulda just given it to you and made the next 6 years of your life a little cheaper.
  • 5 0
 @zepper: NX steel chainrings are the secret to a long lasting chain. A little noisier than the alloy chainrings but the longevity (and tooth strength for the occasional impact) is worth it.
  • 3 5
 @andrewbikeguide: there's no way I would ever run that weight. It might as well be a boat anchor.
  • 97 2
 "wear resistant aluminum" lol
  • 16 1
 As long as you only wear it in your pockets and not on your bike.
  • 6 0
 Waterlogged aluminum has been plauging MTB components for years.
  • 1 0
 Did they change that part? I don't see it but I am also good at missing things ha.
  • 2 0
 @Takaya94: The caption on the second photo.
  • 1 0
 For the effort put into this, why not hard-anodize the fancy little core piece?

Now I mean the actual thick Type III anodizing "hard" like what is used on your fork stanchions.
  • 1 0
 39 grams? I think that's a typo, they meant to say it would last 39 minutes!
  • 2 0
 @Mac1987: It'll definitely wear out your pockets, too.
  • 1 0
 @henreality: fair point, although it won't wear out the aluminium as fast
  • 90 7
 "500 prototypes, and thousands of kilometres of testing", so each prototype averaged a minimum of 4km?

Would be more convinced by hundreds of thousands of kilometres, given the amount of protos.
  • 130 1
 This guy divides
  • 13 1
 @browner: he did the math
  • 23 0
 @browner: This guy This Guys
  • 11 0
 Probably did 499 prototypes that didn't remotely work, and then tested the first good one properly
  • 19 0
 More prototypes than sales!
  • 3 0
 I fear not 500 chainrings tested for 4km but the chainring tested for thousands
  • 39 3
 The alu core is great but those narrow wide profiles are going to wear so quickly you'll be dropping chains like the noughties after a couple rides
  • 9 4
 Good observation. Useless product.
  • 14 1
 and we are off to the comment section to see what experts think Big Grin
  • 12 0
 Also, if you're gonna do a core out of metal for longevity, surely titanium or steel would be the preferred material.
  • 5 0
 Perhaps it would be better with aluminum teeth and carbon spider?
  • 1 1
 This is your conclusion that you reached with this very special test eye? You should work for gemini. It would have saved them 3 years and those 500 prototypes.
  • 2 0
 @Crossmaxx: a thin titanium core seems like a logical choice... actually, a titanium chairing is a logical choice at this price point! Lighter or similar to Aluminum and as durable as steel!
  • 2 0
 @phatcapone: You'd be amazed at what companies can ignore to make an idea work, i have no doubts it's just as durable in the tooth profile with that alu core and it will still work fine with the narrow wide worn, hence tchnically it will last as long, but having seen how quickly carbon wears down when it's rubbed by things like cables, or foot rub on cranks i have a hard time believing the chain retention of the narrow wide won't be compromised pretty quickly.
  • 38 2
 Make it steel all the way to the bolt centres, lose the carbon, drop it to 1/3 of the price and you've got yourself a customer!
  • 8 1
 My Wolftooth stainless steel chainring cost ~£100 but damn they last a long time.
  • 28 1
 My steel chainring from Raceface was 20 bucks and lasts easily over 5000 km of enduro riding
  • 18 1
 @fartymarty: Sram do a steel ring for £15...
  • 4 0
 @fartymarty: even the wolftooth aluminum chain rings last a long time.
  • 10 0
 Still shocked how few people run steel rings given how long they last. Little extra weight in the bottom is no problem!
  • 5 0
 @bashhard: same here,those chainrings are top value
  • 3 1
 I think they went with aluminum core because it will outlast the carbon of the chainring. It's going to be worn down so fast that using steel or titanium or anything actually hard would be a waste.
  • 29 0
 "The claimed weight is just 39 grams (30 teeth)."

"It's available with 32, 34 & 36 teeth (30 and 38 coming soon)"

Ok
  • 8 1
 Yes, the claimed weight is for a 30-tooth version which you currently can't buy.
  • 3 0
 They should have done that the other way; "It's available with 36, 34, 32, wait no just 30 teeth now... Ah dang"
  • 2 0
 No 42? I'm out.
  • 24 0
 Wait. so it's cheaper and lighter than a xtr chainring? That's impressive
  • 34 1
 Or an XTR chainring is ridiculously overpriced.
  • 13 0
 You're wasting money if you don't buy it!
  • 17 0
 I think we have to all admit, that that price was waaaaaay lower than we anticipated! LOL
  • 18 1
 The chain looks heavy.
  • 15 0
 Surely the matching carbon chain is in development now.
  • 3 2
 @ReformedRoadie: ebike specific carbon
  • 15 1
 When did Friday Fails change?
  • 10 0
 I really like the concept and how the turned it into a thought through product. The look is not my style but I'm nopt part of the aero gang.

Btw: Googling the product name before launch helps Wink --> Gemini Rigel
  • 1 0
 I was curious, but not that kind of curious…
  • 9 0
 It would be way more aerodynamic without all those fins sticking up - look more sleek too.
  • 9 0
 I'm sensing a lack of finesse during the following comments
  • 4 0
 it wasnt mentioned in the article, but this is the same company that make the 650E 1 piece carbon bar/stems, that have also featured on PB

my question wouldnt be chain wear life expectancy, its how does it cope with rock strikes..
  • 6 0
 I'm not mad about anything except the "Designed and Handcrafted by Gemini in Barcelona" etched in white. Looks awful on a nice looking chainring.
  • 8 0
 Sharpie sold separately
  • 4 0
 @bushbush: I wore my Sharpie out blacking out "Maxxis" on my tires due to my contract with CST.
  • 7 0
 Is this a little dumb? Yes
Do I wish they made a 48t for my gravel bike? Yes
Would I impulse buy a 48t? OF COURSE!
  • 7 1
 "unmatched durability for a carbon chainring"
How many carbon chainrings are there on the market to compare to?

No I'm not going to bother looking that up.
  • 9 3
 Get a steel chainring, forget about the few grams saved and ride that chainring for 5000 km.
  • 5 2
 I love the irony of products like this in an industry that loves to pretend it cares about the environment... Honestly don't know if the folks creating this shit are doing it in the name of ironic comedy or just general cluelessness but it's good comedy either way.
  • 8 0
 Just to play devil's advocate, this does look like a perfect application for "scrap carbon" that's too short for most other applications.
  • 6 0
 And I love the faux gotcha journalism of people thinking mountain bikers think they are saving the environment.
  • 2 0
 Never discount weight savings- we at carbonXScycles have been using carbon front chain rings for over 8 years ( cnc cut from sheet ) We have never replaced one yet. they are surprisingly robust and seen to be self lubricating.
  • 1 0
 "surprisingly robust and self lubricating"
  • 2 0
 @HughBonero: I'm constantly on Tinder looking for that exact same description. I'll be swiping right when I find her.
  • 1 0
 @HughBonero: like a vagina
  • 6 1
 "why does a dog lick it's ballz?"
"BECAUSE IT CAN!"
Another dog ballz product hits the airwaves!
  • 3 0
 cermaic speed could learn a thing or two about pricing from these guys. 125 euro is by no means cheap, but it isn't horrendous either. At least you can see where the money has gone.
  • 2 0
 You can be all negative about it, and for most of us this is completely not applicable, and I would never buy this product , but there are a few reasons I like it:
1 It is a cool technology that looks like it could carry over to other parts and industries (cassettes anyone?)
2 The weight saving is pretty substantial if you look at it in a relative way
3 It's so obviously a race day only product, that is just awesome.
  • 4 0
 I reckon it looks awesome. Unparalleled finesse also sounds great and is much less likely to meet expectations!
  • 9 0
 But I so prefer parallel finesse, things go sideways when it's unparalleled.
  • 1 0
 @mrdimi: mmmmm.... perpendicular finesse
  • 4 0
 It costs less money than I expected from the headline, but it also contains less carbon than I expected from the headline.
  • 1 0
 "It's designed to be compatible with any 11 or 12 speed chain on the market, including Shimano, SRAM Eagle, and SRAM Eagle Flattop chains. It's available with 32, 34 & 36 teeth (30 and 38 coming soon), with a standard 3 mm offset (Boost)."

Someone with more knowledge correct me if I'm wrong but doesn't SRAM Transmission use a 55mm chainline which would be 0 offset rather than a 3mm offset?

See charts here: www.wolftoothcomponents.com/collections/mountain/products/direct-mount-chainrings-for-sram-cranks
  • 1 0
 Well. If that core was made of steel, making the chainring weight the same as an aluminium one, but costing twice as much and lasting twice as much, it would be even. As it is, 125€ for a 20 gram saving, does not pass the 1 extra euro for 1 less gram treshold.
  • 1 0
 This is filed under the UC or EC (excessive or unnecessary complication) now if our friends from Spain were to go the extra mile and have a topology optimised 3d printed titanium ring you’d have a engineered solution rather than some interesting but slightly incorrect solutions. - wonder if it’s the same guys that were producing carbon fibre brake discs a long time back?
  • 3 0
 I just don't see the point. Saving 20 grams in a high wear location. Why would you?
  • 2 0
 Wait until all that wear resistant aluminum corrodes inside the carbon. By then, it'll be another 20g lighter, Woohooo! So, um, what's wrong with the 59g of steel?
  • 1 0
 Isn’t Gemini part of Unno?
And for “forged” carbon, that’s just randomly chopped cloth, either pre preg or dry. No uniformity etc.
  • 4 3
 Exactly my thoughts. I will stick with my stainless steel Wolftooth rings that last forever and weigh less than a good dump.
  • 4 0
 @fartymarty: to be fair, that's a pretty small dump.
  • 2 0
 @woofer2609: my girlfriend says it's perfectly adequately sized dump.
  • 3 0
 I'm only buying one if they come up with a carbon chain too
  • 1 0
 Give it a few months.
  • 2 1
 So a carbon product that everyone else says carbon just isn't a suitable material for? Where have I seen this before? Something called titan?
  • 3 0
 Finally!
  • 3 0
 Why?
  • 3 0
 More crap nobody needs
  • 2 0
 "...for a carbon chainring." is quite the qualifier.
  • 1 0
 Sometimes I think some people in the industry must think bikers are just a bunch of idiots who would buy anything!
  • 1 0
 Well, brand like ceramic speed, absolute black, cascade component are not bankrupt yet so yeah, there are idiots that buy these shits.
  • 1 0
 @CaSentLeTabarnakMonHomme: dentists are well educated people no?
  • 1 0
 @Compositepro: G W Bush too is well educated...
  • 1 0
 "unparalleled sense of finesse during pedalling."

When your company has 1 engineer and 82 marketing associates.
  • 1 0
 How are they handling galvanic corrosion?
  • 1 0
 will it will last long enough for that to be a problem
  • 1 0
 I wanna see crash test of this chainring!
  • 3 2
 "unmatched durability" you mean maybe 2 rides........
  • 3 2
 why are brands obsessed with weight saving instead of durability
  • 12 1
 You mean, making parts that don't last long and cost more?

erm, well, I do have one hypothesis
  • 2 0
 @Mr-Gilsch: COMMUNISM

obviously
  • 1 0
 It should say "infused with helium" somewhere.
  • 2 0
 Dangerholm approved
  • 1 1
 Dangerholm has been working with Dward Designs to produce this beauty: dward-design.co.uk/product/dangerdward-titanium-chainring
  • 1 0
 @Bitelio: ah, they also sell a titanium bashguard for £96! (Wait, would I even need that if I just use a steel chainring?)
  • 1 0
 @rvdoever: yes they do. And it is a beauty. You can use it or not, it's up to you.
  • 1 0
 I'll wait for their carbon brake rotors
  • 3 0
 Carbon rotors were around 10 years ago.
  • 1 2
 Likely to suffer from thermal expansion weaknesses at the carbon to alloy interface. Makes no sense combined with a metal chain. Only sensible use is with SS belts.
  • 2 0
 Doubt it. The resins that are used these days are incredibly resilient to UV and heat. Your alloy chainring will be more susceptible!
  • 1 0
 Weight weenie things are so resin-ating!
  • 1 0
 I'm not mad at it. It's more affordable than carbon cranks.
  • 2 0
 Beautifull. I like it!
  • 2 2
 Pair this with the new AXS and shift under load... watch it fold like a origami
  • 2 5
 pinkbike is such full of haters. would i buy this product? nope. is it a bad product? nope. maybe it has been done, but i've never seen anything that was aluminum, but wrapped in carbon to reduce weight, and/or increase strength.

this product might not be the next big thing, but it could lead to the next big thing.
  • 1 1
 Take my downvote!
  • 1 0
 This is stupid, and I like Gemini products.
  • 1 0
 Dangerholm has entered the chat....
  • 1 0
 Can manufacturers start making more steel chain rings please?
  • 1 0
 I finally feel complete....
  • 1 0
 Or, save the money and take a 500 gm crap
  • 1 0
 Make MTB cheap again
  • 1 0
 Supererogatory.
  • 2 2
 Raaaaaaaaaaaaah rage the Pink bikers, total click bait suckers
  • 1 0
 Paper would be lighter.
  • 1 1
 This will be the source of a future Friday Fails for sure.
  • 1 1
 I hope it is compatible with the moped I don't have.
  • 1 0
 KOM here I come!
  • 1 0
 Nope!
  • 1 0
 Raceday chainring.
  • 2 3
 Disposable after 1 XC race?
  • 1 1
 That can GTF
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