Why SHIFT? Internal Gear Hubs vs. External Belt Shifting Systems

 Veer's Shift Drive system next to Enviolo internally geared hub system with VS. between them

 

Sean Hacking, Founder/CTO of Veer and inventor of Shift Drive here.👋

In the bicycle transmission landscape, two systems have risen to prominence: chain and derailleur systems and internal gear hubs (IGH). Each are amazing technologies that offer unique advantages and have been refined over decades into efficient, flexible, and relatively lightweight drive systems.

However, if they were perfect, there would be no reason for Veer to exist and why so many other companies are working on solutions as well. 

Closeup of Veer beltring on mid-drive motor ebike

The advent of carbon reinforced belt drives and electric propulsion in bikes has changed the equation, exposing the flaws of our current technology, as well as opening up new possibilities in ultra-durable, lightweight, maintenance-free shifting solutions.

Founder Sean Hacking holding up Veer's Shift Drive system to camera

Veer's SHIFT Drive is the first external shifting system for belt drives, and a completely new take on transmissions in general. But it's not enough to be new, it has to solve problems for people, and have a reason to be built.

View of bike chain from front of crank looking back showing chain line is not straight

 

Carbon belts can't be angled from side-to-side like a chain can as it traverses the gears on a cassette, meaning using a derailleur with a belt is not currently possible. This leaves us with internal geared hubs and gearboxes to enable shifting with belts, which offer better reliability and lower maintenance, but come with some significant compromises.

Internaly geared hubs on two bikes leaning against nike rest on city street

As an engineer, I wanted to love them, and when I started Veer, I bought or test-rode every geared system on the market to find out what was the best pairing with a belt drive. I was left disappointed. The high mass, lower efficiency, poor shift performance, and relatively high cost were deal-breakers for me and apparently for the >90% of riders who still choose derailleurs and chains.

 

There had to be a better way, one that combines the benefits of derailleurs with the reliability and low maintenance of geared hubs and belt drives. In 2019, I was sitting under a White Pine, backpacking alone deep in the California wilderness. The concept of Shift popped into my head, fully formed.  Instead of moving the belt in-line with different sprockets on a cassette, why not move sprockets into line with the belt? That would require disengaging the belt from the sprocket to change gears, unless you split each sprocket up into sections and move them in-line one-by-one. This concept formed the basis of the patented Shift Transformer technology, which maintains constant belt-sprocket engagement at all times. Simple enough, but the details took the next four years to perfect.

Why do we think Shift Drive has a place in the market when there are already so many good options? Here is a detailed comparison to help answer that question.

 

(Keep in mind that some of the details are less relevant for expensive high-end shifting systems like Pinion, Classified, or Rohloff, unavailable to most riders when they add thousands of dollars to the cost of a bike. This is a comparison with the most popular gear systems on the market)

 

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Internal Gear Hubs – A Closer Look

 

*Key Benefits:*

  1. Low Maintenance
  2. Durable and Long-lasting
  3. Relatively Consistent Shifting
  4. Shifting While Stationary
  5. Gearing is protected from the elements

 

*Key Drawbacks:*

  1.  Heavier Weight
  2. Up to 15% Energy Loss
  3. Relatively High Cost
  4. Complex Repairs
  5. Inefficient Upshifting Under Load
  6. Not compatible with Hub Motors
  7. Bike Design Limitations
  8. E-Bike Durability Issues

 

Introduction:

 

Internal gear hubs have long been valued for their low maintenance and durability, making them an attractive choice for urban cyclists and commuters. Their enclosed design protects the gears from elements, thereby extending their lifespan and ensuring consistent performance. A unique advantage of IGH is the ability to shift gears while stationary, a feature particularly beneficial in stop-and-go city traffic.

 

Cutaway of Rohloff hub so you can see inside mechanics

 

Complexity and Efficiency:

 

However, these hubs are heavier than their derailleur counterparts, which can affect the bike's handling and increase rider fatigue. They also suffer from efficiency loss due to internal friction, leading to up to 15% energy loss, reducing range and slowing down the rider. The complexity of these hubs translates into higher costs, both in terms of initial investment and potential repair expenses. Their intricate internal mechanisms often require specialized skills for maintenance and repair.

 

Shift Performance and Compatibility:

 

In terms of performance under load, internal gear hubs struggle to upshift efficiently, which can be a drawback in varying terrain or for cyclists who need to change gears quickly. In fact, most simply will not upshift under high pedaling forces. They can't be used with popular rear hub motors, posing a challenge in the growing e-bike market. Design constraints imposed by these hubs also limit the flexibility in axle types, wheel designs, and dropout types. For e-bike users, the added torque often leads to premature failures, as evidenced in models like the Shimano Inter-5E and Kindernay XIV, which are specifically designed for e-bikes but have still shown decreased durability when used with electric power.

 

 

External Belt Shifting Systems – Breaking New Ground

 

Angle of the rear of Veer's Shift Drive on a bike and somone riding it

 

*Key Benefits:*

  1. No efficiency loss from gearing
  2. Lightweight Design
  3. Simple to Build and Repair
  4. Smooth Shifting Under Load
  5. Wide Compatibility
  6. Flexible Design Options
  7. Drops in on hub motors
  8. Suitable for High Torque Applications

 

*Key Drawbacks:*

  1. Limited Gear Range
  2. New on the Market

 

Introduction:

 

The advent of external belt shifting marks a significant innovation in bicycle transmission technology. Shift Drive is designed to combine the efficiency and performance of derailleur systems with the low maintenance and durability of belt drives. They stand out for their affordability, high efficiency, low weight, and completely smooth shifts, even under high torque.

 

Simplicity and Affordability

 

One of the most notable advantages of Shift Drive is lightweight aluminum design. Weighing about a quarter of most gear hubs, it significantly enhances bike handling and reduces rider fatigue. The simplicity in its design makes them both cost-effective to produce and easy to repair, addressing one of the main drawbacks of internal gear hubs. The cost is comparable to popular low-end hub gear solutions, while offering shift performance better than any system available today (with the possible exception of the Classified Powershift).

 

Fully Sealed

 

Although the shifting action may look complex, that is only because it is visible on the outside. There are about 10 times fewer parts in Shift than in most gear hubs, and only a few stamped steel parts, compared with dozens of machined steel gears and clutches in the typical gear hub. Every moving interface is fully sealed from the elements, just like the best hub gears.

 

Gear Range

 

One side- effect of this simplicity is their gear range. With two gears and 140% gear range, they may not be suitable for all cycling conditions. While more speeds are coming, the first systems are optimized primarily for urban use. Despite this, feedback suggests that in urban e-bike applications, where motor assistance is prevalent, this range is generally adequate.

 

Shift Performance and Compatibility

 

Veer's Shift Drive system being installed onto standard HG freehub body on a rear wheel

 

These systems excel in shifting performance, particularly under load, offering a smooth and instantaneous experience for cyclists. Their compatibility with standard freehub bodies is a significant advantage, allowing for greater flexibility in bike design without the limitations imposed by internal gear hubs. This compatibility extends to various dropout types and with the built-in tensioner, is even suitable for many full suspension bikes. No design changes are needed on the majority of bikes transitioning over from a chain-based system. Additionally, they are built to withstand the high torques typical of e-bike use, ensuring durability and reliability in this rapidly growing segment.

 

Summary

 

In summary, while internal gear hubs offer a low-maintenance and durable solution, their drawbacks in terms of weight, cost, and efficiency, coupled with performance issues under load and compatibility challenges, present significant limitations. On the other hand, external belt shifting, with its high efficiency, lightweight design, and broad compatibility, offers a compelling alternative, especially for e-bike users and those seeking a more versatile and worry-free cycling experience.

 

As the bicycle industry continues to evolve, the choice between these two systems will largely depend on the specific needs and preferences of the rider. Whether it's the reliable and protected performance of internal gear hubs or the innovative and efficient nature of external belt shifting systems, both technologies play a vital role in shaping the future of bicycle transmissions.


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