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Bike Shop: The Pinion C1.12 Gearbox

Taking an in-depth look at an alternative to classic drivetrains

The easiest way to think about Pinion's complicated C1.12 gearbox transmission is by envisioning a triple chainring. Yes, we all know triples. Three rings in the front conduct gross changes to gearing while our cassette manages nuances.

Pinion also uses three multipliers but unlike triples, there is no overlap in Pinion's C1.12 gearbox. This means you have 12 completely unique gears, each evenly separated by 17.7-percent steps to compose a massive 600-percent range.

That sounds like a lot of range. It is. SRAM's Eagle is 500 percent. Yep, 600 is enormous.

But Pinion's internals look nothing like the cassettes we're familiar with. Peering within the black box looks to reveal the innards of an evil clock tower. Like the one in "Dick Tracy." Ok, fine, it was a drawbridge, but either way, there were massive, round, metal interlocking circular gears ready to crush a damsel in distress. Pinion uses these gears, so they're evil-guy approved, which is nice.

The gearbox is sealed and contains four-season gear oil that you're instructed to change once every 10,000 kilometers (6,213 miles) or once a year, whichever comes first. Challenge accepted.

The sinister, toothy interlocking discs are a combination of spur gears and a helical gear. When they interface, they create a gear ratio based on the teeth of the two rings, just like your front chainring connecting to a cog on your cassette via the chain, simple enough. Rather than have 12 round metal gears engaging with another 12 round metal gears, making for an enormous gearbox, Pinion uses three multiplier gears. We'll get into the specifics of how this works, but for now, just think of the multipliers like a triple chainring, causing gross changes in gear ratios.

Ok, understood on our triple analogy, but how does Pinion's gearbox actually work? It's a game of shafts but never getting shafted. For starters, there's a top shaft and bottom shaft, both stacked with gears. Seven gears each in the case of the C1.12. But let's break the system down to its six essential parts, and these are Pinion's names:

Input Shaft. It's the bottom shaft. This is what the crank spindle slides through. The four gears closest to the non-driveside are permanently mounted to the input shaft, like a pinecone. Force transfers through the crank's spindle to the input shaft, enters the gearbox, and the magic show begins. 

First Sub-Transmission. This is composed of the four non-driveside-most gears on the top shaft and the four corresponding gears on the lower shaft. Pedal force travels from the Input Shaft through these gears first and creates the initial gear ratio. That force travels through only one pair of corresponding gears at a time, but we'll cover that later.

Second Sub-Transmission. This consists of three driveside-most gears on the top shaft and their corresponding three on the lower shaft. These pairings create a gear ratio that further multiplies the initial gear ratio. Although force travels through these second, think of them as your front chainrings, as they cause big changes in ratio. Again, only one pairing is engaged at a time.

Output Shaft. This is a hollow tube that fits over the driveside of the Input Shaft, right back where we started. It is able to spin freely on a set of needle and cartridge bearings. The lower three of the gears of our 'triple chainring' analogy are permanently fastened to the Output Shaft. On the outside, the chainring is affixed to the Output Shaft.

Shifting Shaft. This is the upper shaft where seven gears spin freely and independently from one another. Or, at least, they would if their teeth weren't locked against those of the gears on the Input and Output shafts. Embedded in the hollow Shifting Shaft at the center of each of these gears is a pawl which, when activated by the cam shaft, locks the gear around it to the Shifting Shaft. One gear from the First Sub-Transmission and one from the Second Sub-Transmission will be engaged at all times, and the multiplying combination determines the overall gear ratio.

Cam shaft. This resides within the Shifting Shaft. Two cables entering the front, non-driveside of the Pinion gearbox spin a tiny planetary gear on the end of the Cam Shaft and rotate it, causing specific pairings of pawls to flip up or down, orchestrating the shifting process.

How it all comes together: Example time. While we pedal along, the force moves from the Input Shaft to the Shifting Shaft through the connection between whichever pair of gears we've engaged in the First Sub-Transmission, creating our initial gear multiplier. The force then moves along the Shifting Shaft to the gears we've engaged in the Second Sub-Transmission. Next, the force travels to the Output shaft, which is connected to the chainring. If the multipliers propel the chainring at a speed faster than the cranks, you'll be in a harder gear. If it is going slower, you'll be in an easier gear.

The Pinion gearbox poses a new solution to an unchanged arena of bicycle design: shifting. Yes, incremental changes have evolved into 1x systems spanning large ranges with impressive actuation, but they still rely on a derailleur, quick to be marred by a malicious rock. Pinion brings robust range through German over-engineering. Worth its weight? Ride one to find out.

Interest in what it looks like on a bike? Check out our test of the gearbox-equipped Zerode Taniwha.