The Binary Gear is a 2-Speed Bottom Bracket Gearbox

Jun 9, 2023
by Dario DiGiulio  
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MagneticDays is an Italian equipment manufacturer with a background in resistance training machines and trainer components. With their first foray into the outdoor cycling world, they're unveiling a new project: the Binary Gear, a two-speed gearbox that integrates directly into the bottom bracket of an existing frame. With a cable-actuated shifter, you can switch between a 1:1 ratio (same as a static ring) and a 1:1.25 ratio (chainring rotating 25% faster than cranks).

If you take a look at the video below, you can see the increase in gear ratio that the Binary system can provide. There's also a quick shot of the cable actuation that happens around the bottom bracket.


The one standards hitch that the Binary system runs into is the bottom bracket standards it fits within. At this point, the gearbox can only fit into T47 and PF46 bottom brackets, as the outer diameter of the gears are too large for smaller BB shells. The team at MagneticDays says there's a smaller BSA68 version in the works, following the Kickstarter launch.

Speaking of Kickstarter, that's the avenue by which the Binary Gear is set to come to life, with a $32,000 USD goal to get things off the ground. On their Kickstarter page, MagneticDays is featuring some shots of the prototyping process, which is one of the few glimpses into the inner-workings of their novel design.

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Cable actuator and a shifter pod. It's unclear what the flatbar shifter will look like, but this is a reasonable form factor.

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Some of the internal gearing, and an early version of the crankset.

The cranks they've developed in tandem with the project have another interesting trait, beyond their integration with the gearbox. They've added a 3-position flip chip at the pedal threads, allowing you to change the effective crank length by simply removing the pedals. This gives the user the option to run 170, 172.5, or 175mm cranks, to suit their specific fit. Obviously those lengths are biased a bit towards the road/gravel end of the fit spectrum, but it wouldn't be too hard to shorten things up and better cater to mountain bikers.

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Visually, this non-drive side actuator is the only thing out of the ordinary.

There isn't much information on the Kickstarter page about exactly how the gearing works within the Binary, but from what we can tell it's a series of toothed cogs translating movement from the cranks to the chainring. Drag is typically a downside that comes along with any sort of mechanical gearbox, so it's safe to assume that there will be some here, though no numbers are quoted in the campaign.

The current pledge price to get a Binary Gear setup is €267, with an estimated final retail price of €890.

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You can find more information on their Kickstarter page.


Author Info:
dariodigiulio avatar

Member since Dec 25, 2016
167 articles

66 Comments
  • 105 0
 Never knew my bike's cranks were non-Binary.
  • 13 1
 At least they are already they!
  • 35 0
 most cranks do go both ways
  • 47 0
 My XT cranks also stopped identifying as XT cranks after heel rub from three rides
  • 10 3
 @Mac1987: maybe if you didn't rub your heels so much, your cranks wouldn't have identity issues.
  • 4 0
 @Mac1987: sounds like you have an alignment problem.
  • 40 0
 Aahhh...that's what LGBTQI stands for! Lower Gear Between The Q-factor Interface.
  • 10 0
 Should go well with a transaxle.
  • 2 0
 @olngjnsn: But they would lose stiffness!
  • 2 0
 @Mac1987: Ahh yes, the " I" cranks. They are like 0.00001g lighter though.
  • 54 0
 T47 comes out.....

Engineer - "I can totally stick an entire gear assembly in that mamajama"
  • 29 0
 Flip chip in the crank so you don't get the extra leverage but still enjoy all the rock strikes of a 175. Nice!
  • 5 3
 It's fine, the extra length actually protects the pedal.
  • 6 3
 @DavidGuerra: guess you have never rock striked and it bucked the back of the bike up and crashed
  • 4 0
 @solarplex: No, just pedal hits on rocks.
  • 22 2
 Chainring rotating 25% faster than cranks sounds nice until you find out there's a 20% drag.
  • 12 0
 And we're back to the world of Hammerschmidt/Schlumpf... With only a 25% over speed that's quite a lot less than a road double, which is about 45% between the rings. And it's only the difference between a 42T and 52T on the cassette, so wouldn't enable you to run a short cage rear mech and a light, compact cassette. Hammerschmidt had a 1.6 over drive, Schlumpf is/was 2.5, which frankly seems excessive
  • 4 0
 The cage on a 42T could be a fair bit shorter than 52T. Think Shimano 11 speed vs 12 speed.
  • 7 0
 I’ve still got my Hammerschmidt! Will sell for $600 USD
  • 1 0
 Lol Hammerschmidt that’s a name I haven’t heard of in ages. Really dating ourselves here!
  • 4 0
 Came to the comments to find “Hammerschmidt”
Starting to wonder if MTB is cyclical like fashion…
  • 3 0
 I rode a Sclumpf on a Spot steel 29er around the XC course at Sea Otter. One of the most memorable rides I've been on. I hit the crank button when I wanted to and didn't when I didn't want to. It was amazing.
  • 2 0
 What this one is lacking compared to Hammerschmidt is the bash protection and chain retention. Either way, the small chainring of both systems put a lot of additional stress hence wear on the chain and sprocket. so that's one thing to keep in mind. Schlumpf is still there, isn't it? At least on (mountain) unicycles. Kris Holm did quite well at the BCBR riding one of these.
  • 1 0
 really liked my hammerschmidt back in the day. i liked it better when i took it off and went to a wide range cassettte and narrow/wide sprocket.
  • 1 0
 @mountainsofsussex The Schlumpf also has a 1.6, which is what I rode.
  • 1 0
 @iamamodel: ah, ok, that seems more sensible!
  • 7 1
 I love the attempt, maybe the simplest version of the gear box can bring practical innovation where the full deal doesn't realy have a great wide ranging application... I suspect it won't be for gravel though, where unsprung mass isn't a factor... Maybe they should have focused on MTB > smaller rear cassettes and derailleurs mean meaningful weight loss gains to unsprung mass > suspension performance. Regardless, cool innovation and hope it goes somewhere
  • 7 0
 Gravel will be all over this, it allows them to pretend they have 2x system without actually having to deal with a front meh
  • 5 0
 Gear resolution is more important in road/gravel riding though, so being able to run a tighter ratio rear cassette with a wider gear range is advantageous in many scenarios. And its why drop bars are often still sticking with 2x systems.
  • 5 0
 I left my 2x10 on my old Kona Explosif because it's just so good bikepacking to know you've got a granny ring to save your ass, also nice thick strong chain! So I love the concept of this but can't really see where it's going with an estimated retail of € 890.
  • 5 1
 "Obviously those lengths are biased a bit towards the road/gravel end of the fit spectrum"

No, they're biased to exactly what is specced on modern mountain bikes. Yes, there are experiments with shorter cranks, but "the fit spectrum" is still definitely in the same 170-175 range
  • 4 0
 Thank you. I was about to post this as well. It seems like Pinkbike loves to push the latest trend (and people have been trying shorter cranks forever) as the new standard.
  • 8 0
 this is cool.
  • 1 0
 As featured on Mior Mior VT!
  • 2 0
 @ridedigrepeat: yes. do you want my autograph?
  • 4 0
 If they can equal the low drag numbers of the Classified hub I think they have a winner here. If it's closer to Hammerschmidt territory I guess it will go the same way as that.
  • 6 0
 Just bring back the Hammerschmidt already.
  • 4 0
 Maybe someone will invent a system where you have 2 different chain rings on the front that you can use a cable actuated device to switch between
  • 1 0
 "from what we can tell it's a series of toothed cogs translating movement from the cranks to the chainring"

And the internet is a series of tubes. "What you can tell" is nothing. A good guess based on the form factor and size limitations is a small planetary gear set and the cable selects which portion is locked, probably via that ratchet/cam shown if the pic (it's not internal "gearing").
  • 1 0
 I thought that a company was going to something like this a while ago. The concept makes sense to me because there is extra space in the BB bracket and all you need is 2 gears to make a big difference. I think it has to be able to shift under load, though. We will see if it works in the MTB real world.
  • 3 0
 Back to a square taper BB spindle? Nice! Now where did I put those old Raceface North Shore crank arms...
  • 5 0
 Classified
  • 3 0
 A modern take on the hammerschmidt, will be very interested to see how it goes!
  • 3 4
 We want a gearbox/ebike motor combo, all of the weight on the bottom bracket where it belongs. Only good solution so far seems to be Intradrive, but that isnt even out yet. I refuse to buy an ebike with any of these garbage dérailleur systems.
  • 3 0
 Combined with the Classified hub, you get a 4-by system. Nice.
  • 4 0
 Or this with a 3x12 and a Classified hub. A measly 144 gear drivetrain. A truly gross drivetrain.
  • 1 1
 Interesting, but not practical on its own until it starts getting into the 300%+ gear range with the same losses as a standard drivetrain.
  • 1 0
 the shifter is on a ROAD bike or GRAVEL please find the plot this is about mountain biking. now DV me
  • 2 0
 very cool. I'd love to try this on a singlespeed setup.
  • 2 0
 *binaryspeed
  • 1 0
 Dude! I thought the same thing i swear. Ive dreamt about something like this on my last ride for the steep climbs.
  • 5 0
 @mi-bike: dinglespeed
  • 2 1
 You know you can make an easy two speed right? Or get a Shimano hub shift, or stick with the SINGLE speed?

I'm honestly shocked by single speeders saying they want to try this. Why? You've voluntarily gone back in time technologically, why would you want to add this into that mix?
  • 6 0
 @BarryWalstead: I love riding single speed. But I really love riding a dingle speed.
  • 2 0
 Add me to the list of dinglespeed dreamers
  • 2 0
 Nice option for single speeders, lose the dingle cog fussiness.
  • 3 0
 Lose the dingle cog fussiness along with the fact that it's a singlespeed.
  • 1 0
 Keep it. dinglespeed ²
  • 2 0
 Another damn cable. Might as well route it through the headset.
  • 2 1
 Interesting setup. I'd be more tempted if they had 160mm cranks.
  • 1 0
 Analog bike gone digital!
  • 1 0
 And how us the gear ratio paired with that shifting hub?
  • 1 1
 what is old is new again
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