The Birth of EQUAL Control Lever

The Story Behind the Limitless Control Lever

In an era of hydraulic brakes and electronic shifting, GROWTAC's EQUAL control lever stands out by embracing the classic mechanical systems for both braking and shifting. Its key feature is the friction-based design, which allows it to work with any number of gears, any derailleur, and any sprocket combination—making it truly versatile. Development began around 2017, but the product wasn't released until 2024. Why did it take so long? And why a friction-based system in this day and age? We asked GROWTAC's CEO, Mr. Kimura, to share the story behind the development of the EQUAL control lever.

Promises, Promises…

So now that the EQUAL control lever is finally out in the world, what was the concept behind it in the first place?

Kimura："We wanted to create a control lever that breaks down the barriers of manufacturer, grade, and generation." That was the concept and the starting point for developing the product.

So it works with 6, 7, 8, 9, 10, 11, 12, or 13 speeds, and with derailleurs from Shimano, Campagnolo, SRAM, or Suntour—Sora, Dura-Ace, XTR, or Tourney—right?

Kimura：Exactly. With a mechanical derailleur, you can make almost anything work. There are no restrictions on sprocket combinations either. As long as the capacity and slant angle match, you could even shift a 12-speed cassette with an 8-speed derailleur. The shifting performance will, of course, depend on the combination.
It doesn’t matter whether it’s the front or rear. You could even use the left lever to actuate the rear derailleur.
The lever is fundamentally designed to accommodate two cables on one side, allowing for future expandability.

So this really can do just about anything. It's a product that embodies the EQUAL concept exactly. Its release was delayed repeatedly, and in the end, people were jokingly calling it the "Promises, Promises…" project (laughs). When did development actually start?

Kimura： Development started around 2017. Considering the concept of being able to operate with any number of speeds, it wouldn't work to limit it to "11-speed only" or "only works with 12-speed" like major manufacturers. It had to operate continuously without such restrictions.

So you couldn’t achieve this with the ratchet mechanisms in existing shift levers, right? Those with fixed gear steps just wouldn’t work. You had to completely rethink the structure

Kimura：Exactly. You need to understand that the lever basically doesn’t have any indexing. Initially, we planned to make something much simpler—like an evolved version of a retro shift, with a W-lever attached to the shift lever. However, having a W-lever that doesn’t return after being moved made it very hard to operate. We realized we needed a shift lever that comes back after being used, so we changed direction halfway through, which ended up taking a lot of time before release.

Letting Go of Two Years of Effort

So, tell us about that back-and-forth development story.

Kimura：At the start of development, the structure was completely different from what it is now. Initially, there was a single shift lever, equipped with a thumb lever and a winding lever, which returned to its original position after being operated. To achieve the motion where the lever returns to its initial position after a shift, we originally used a mechanism called reverse input lock.

Kimura: This (see photo below) is the reverse-input lock mechanism. The center is fixed, and turning the left shaft also rotates the right shaft. However, if you try to turn the right shaft, it locks and cannot move—it's a complex one-way clutch. Attaching the shift lever to the left shaft and connecting the cable to the right shaft blocks force from the derailleur while transmitting force from the lever.

I see. So instead of using friction to resist the derailleur spring, it’s mechanically locked — which means it can be turned with light force.

Kimura:That’s right. We spent about two years developing it, but we just couldn’t eliminate the backlash, and it didn’t feel right. The lever would slip slightly when you tried to shift. The mechanism was complicated, the parts were tiny, and we couldn’t achieve enough rigidity. Since the mechanism itself was covered by another company’s patent, we worked with that manufacturer for about two years — but in the end, it didn’t work out. We had to abandon it, and that was a really painful decision.

At that time, the development engineer seemed quite exhausted.

Kimura：He worked hard for two whole years, but I ended up criticizing his work. I really made things tough for him (sorry about that).

You must have found it really difficult to decide to scrap the reverse-input lock mechanism, which took two years to develop, right?

Kimura：We gave it our all over those two years, so I wish we had switched direction sooner.

A return to the approach to friction

So you decided to scrap the reverse-input lock mechanism and go with the friction-based system instead, right?

Kimura：Yes. Basically, it's the same as a W-lever, but with a W-lever, once you operate it, it stops in place and doesn't return. The EQUAL control lever, on the other hand, returns to its original position. Making it return to the original position is really challenging. We realized that the feel wouldn't improve unless we minimized backlash in the shaft's movement, so developing the clutch for returning the lever was tough. The current clutch mechanism is what came out of that effort.

So, when you operate the lever, the outer ring moves, the clutch rollers engage between the outer and inner rings to lock, and from that moment the outer and inner rings rotate together. When force is released from the lever, the engagement is disengaged, allowing the inner and outer rings to move independently, right?

Kimura：Exactly. To reduce the number of parts while improving the operation feel, the engineer came up with this unique mechanism. When no force is applied to the lever, it remains free (the shaft can rotate). The moment any force is applied, it must instantly engage and stop—not just in one direction, but both. That’s why a proprietary clutch was necessary. There are plenty of one-way clutches in the world, but a mechanism like this is probably unique.

I’m not quite sure what the role of the switch ring is…

Kimura：To ensure the lever locks the moment force is applied, a part called the switch ring is incorporated between the outer and inner rings (the switch ring is attached to the lever). When the lever is moved, the switch ring moves, pushing the clutch rollers into the gap between the outer and inner rings. This ensures that the clutch rollers are already engaged and locked when force is applied to the lever, minimizing any time lag. The switch ring was also uniquely developed. The outer ring is not just a simple octagon; its angle and shape were repeatedly refined to achieve the perfect result.

So if the switch ring moves first, that means there’s some play, right?

Kimura：Humans are fairly forgiving; it doesn’t feel strange if the lever wiggles a bit when no force is applied (when it’s not being operated). Shimano is the same in that regard. But the moment you try to operate it and apply force, any "empty stroke" feels off. If the lever gives a slack feeling when you apply force, the feel is bad. We learned this during the development of the first-generation clutch mechanism that was eventually scrapped. We knew the new clutch mechanism would work, but how it would feel was uncertain. Thanks to the switch ring idea from the engineer, which uses human pre-motion to press the rollers against the slope, it worked out perfectly. This is truly the engineer’s achievement. My ideas were sunk after two years (laughs).

So the project that took two years to develop was eventually scrapped, but it wasn’t a waste, right?

Kimura：Exactly. The first-generation development allowed us to understand the correlation between human feel and the machine’s movement. We gained know-how, such as how much backlash is acceptable and the level of precision required. Thanks to that experience, the current mechanism could be realized. Ultimately, the development of this new clutch mechanism also took about two years.

The Struggle Continues

So, the development went smoothly once this new clutch mechanism was completed, right?

Kimura：Not exactly. Human finger strength is surprisingly high, and at first the clutch would slip and spin freely, which was quite a challenge. We had to carefully consider the material, shape, surface hardness, wear resistance, and durability, and in the end, even the grease had to be uniquely developed. It was a continuous struggle.

Oh, the grease is specialized too, huh. One of the major features of the EQUAL control lever is that it can also be used in friction mode. Friction, in this context, is different from modern indexed shift levers that have a clicky feel; it’s a type of shift lever that moves smoothly. The derailleurs have built-in springs that pull the cable (toward the inner chainring for the front derailleur, or the top cog for the rear derailleur). To prevent the cable from being pulled automatically by the spring, friction is used to hold it in place. That’s why it’s called friction. So, in the EQUAL control lever, what actually generates the friction?

Kimura：Friction is generated by stacking seven plates. Plates connected to the shaft and plates connected to the housing overlap, and a spring presses them together to create friction. The friction force can be adjusted using a 3mm Allen key.

So, this friction adjustment is the key to enjoying the EQUAL control lever, right?

Kimura：Exactly. The friction mechanism is placed at the tip of the shaft so it can be easily adjusted. Actually, there’s another feature: a regular one-way clutch is incorporated into the friction mechanism. When winding the cable (front shift up or rear shift down), the friction plates don’t need to rub. If they did, the operation would become extremely heavy due to the derailleur spring plus the friction. The friction plates only need to engage when the cable is being released (front shift down or rear shift up). That’s why the one-way clutch is included. In other words, the friction mechanism always rotates in the same direction. When releasing the cable, the derailleur spring plus the thumb force overcomes the friction, allowing it to rotate.

I see. So that means the friction mechanism and the one-way clutch are at the tip of the shaft, and both lever A and lever B each have their own unique clutch. That makes a total of three clutch mechanisms inside this bracket. It’s more complicated than I expected.

Kimura：It’s kind of like a precision machine.

Kimura：Fitting these three clutches and the friction mechanism into the narrow bracket was also a huge challenge. The bracket couldn’t be made any thicker, so space was very limited. At the same time, we couldn’t compromise on the bracket’s fit or the brake lever pivot position. Our goal was a thickness similar to Shimano’s Di2. In the end, we couldn’t make it as thin as Di2, so we made it slightly thicker, but kept the areas where the fingers move thin, so it doesn’t feel bulky when held. While features like “compatible with any drivetrain” are important at the launch stage, once the lever is mounted on a bike and in use, the fit and feel in the hand become far more important. Poor feel reduces the sense of integration with the bike, so we focused on it. After many NGs and remakes, I imagine the engineer got increasingly exhausted. Thanks to that effort, the bracket shape turned out excellent. Personally, I’ve gone beyond liking it—I love it (laughs).

I agree, it doesn’t feel bulky at all. In fact, it fits even better than Di2.

Kimura：Since there are so many components—friction mechanism, one-way clutch, two unique clutches, pulleys, and the index system—the shaft had to be lengthened, but we packed everything in as tightly as possible. The bearings supporting the shaft also have a clever design. Instead of simply pressing them into the bracket, they’re fixed so they can float slightly, allowing the shaft to move smoothly even if it flexes under finger force. Speaking of which, the band was also tricky.

The band that attaches the lever to the handlebar?

Kimura：Exactly. You’d think this would be easy to make—just bend some metal and drill a hole, right? But when we actually tried, it didn’t work at all. At first, we made it from stainless steel, but it stretched and didn’t provide enough clamping force. We tried various thicknesses, but nothing seemed to work, and we couldn’t spend too much on cost either. Then, by chance, we got to know a factory that used to make clamp bands. It was a fateful encounter. They shared their know-how on materials, bending methods, and heat treatment recipes, and with that guidance, we finally managed to make it.

I don’t mean to be disrespectful, but something that looks this simple really has a lot of depth, huh.

Kimura：If the material doesn’t stretch enough, it cracks; if it stretches too much, it won’t hold. There’s a sweet spot. I don’t think there are many manufacturers who can make it.

Being usable as a friction lever is one of its features, but by adding a part called the click plate, you can also get the familiar clicky feel of a typical shift lever.

Kimura：We also paid attention to the click feel when using the click plate. Two small balls are pressed by two leaf springs. As these balls pass through the holes in the click plate, they create the familiar clicky feel. At first, we tried using just one leaf spring and one ball, but it didn’t give a good feel. Pursuing this shift feel was quite a challenge.

What materials are the lever and the bracket made of?

Kimura：Both are made of resin. I think an all-resin lever is quite rare. Choosing this material was also a big challenge. It's a metal-replacement plastic—an engineering plastic packed with short carbon fibers—and without using it, we couldn’t make the lever light. Since lightness was important for the EQUAL Control Lever, our initial goal was to make it lighter than mechanical Dura-Ace. In reality, we didn’t quite reach that, but it ended up lighter than mechanical Ultegra. The bracket was also tough. You might think rubber products are cheap since they’re everywhere, but rubber with a complex shape is very hard to mass-produce. Shimano probably uses elastomer (resin) injection molding to keep costs down. The EQUAL Control Lever bracket is rubber and has a complex shape, so it can’t be made easily like an injection-molded part. It’s quite costly. I’d say the cost of the EQUAL Control Lever bracket is probably about the same as Shimano’s bracket retail price (laughs). On the plus side, because it’s rubber, it’s water-resistant and can stretch up to 500%, so it’s very durable. Finding a factory to make this was also a big challenge.

For the Realization of the EQUAL Concept

It seems like it was quite a difficult process.

Kimura：It was all just one struggle after another. Making a control lever is really tough. Really.
The development cost ended up being around 100 million yen.

100 million yen…!? To be honest, I don’t think this is the kind of product that will sell like hotcakes, so will you be able to recoup the costs?

Kimura：We don’t really think in terms of “recouping costs” (laughs). As long as the company is still around once it’s finished, that’s enough. If it doesn’t sell, we can just pretend it never existed.

Are you sure that’s okay?

Kimura：If we had taken on debt to force production and then it didn't sell, we’d be in trouble. But as long as the product itself doesn’t carry any liability once it’s finished and the company stays afloat, that’s fine. More importantly, it’s exciting and meaningful to introduce new ideas to the world. There are definitely people who want the EQUAL Control Lever, so it can sell slowly and steadily over time. Plus, challenges bring energy to the company, help develop people, and accumulate know-how. And they lead to the next challenge. In that sense, you could say we’ve already “recovered” that 100 million yen (laughs).

There are many manufacturers that make cranks, chainrings, and other parts. As for levers, there are third-party options for mechanical or electronic types that mimic Shimano. But fully original mechanical shift levers are extremely rare, and the challenge is even greater with continuously variable shifting. You must have known from the start that this would be a difficult project, right?

Kimura：Absolutely. We started from zero with no existing models to follow. But without this lever, the EQUAL concept couldn’t be realized, so we were determined to make it. This is an essential product for achieving the EQUAL concept—it’s almost like a goal in itself. The development took time, but I think it turned out well. There are many complex and delicate design elements, yet once completed, it proved to be quite robust. The placement and arrangement of parts are probably the best they can be.

Now that it’s finally completed, what kind of users do you hope will enjoy the EQUAL control lever, and how?

Kimura：First of all, I don’t think this is necessary for people who are satisfied with Shimano or SRAM, or those who are happy with hydraulic or electronic systems. There’s no need for them to force themselves to use it. I’d like it to be used by people who ride rim brakes and are wondering what to do next, those with a fondness for older parts, or anyone feeling frustrated with current high-end components. It works with any derailleur, so it’s also suitable for people whose levers can’t be repaired due to discontinued support. ...That’s our assumption, but honestly, I can’t predict exactly who will buy it and for what purpose. Many people probably won’t even understand the existence of the EQUAL control lever, so I don’t expect it to sell quickly.

You might need some time to get people to understand this, since it’s a type of component that didn’t exist before.

Kimura：Exactly. The same goes for the EQUAL pedals—since they’re the first of their kind in the world, it’s hard to predict whether people will accept them or how much they’ll sell. That means we can’t really make a production plan. (laughs)

Since the EQUAL control lever is such a “do-everything, overly versatile lever,” I imagine some people might feel unsure about how to actually use it.

Kimura：There are studies suggesting that having too many choices can be counterproductive (known as the "jam theory"). If you line up 100 options, people often don't know what to pick and may lose the desire to buy. With just three options, it's easier to choose and purchase. That may be true. But sports bikes are a hobby, right? Having plenty of choices is part of the fun. Spending time deliberating can be enjoyable too (laughs).
：Honestly, it would have been much easier and probably more marketable to just copy another company's lever, add one gear, and say, "Now it works with 12-speed mechanical systems!" But with the EQUAL Control Lever, I want people to realize, "Oh, I can do things this way," or "I can enjoy it like this." If they come to feel, "Bicycles can be freer and more fun," that would be amazing.