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The 3 Types of E-bike Drivetrains:
Single speed belt drive
A majority of bikes feature the traditional drivetrain setup.
Drivetrain setups like the one on this Enviolo continuously variable transmission do not have any external parts.
Planetary Drive Systems and Bicycle Transmissions: The Rising Popularity of Internally-Geared Hubs on Electric Bikes
Outside of certain cycling niches, internally geared hubs were often seen as the peculiar relative of more commonly used drivetrains.
Bicycle commuters who faced harsh weather conditions, such as snow and rain, appreciated internally geared hubs because all the important components were sealed inside the hub shell, protecting them from the elements. Meanwhile, long-distance bike tourers were drawn to these hubs because they required minimal maintenance and allowed for smooth shifting even when the drivetrain was put under intense pressure. This made them ideal for tackling challenging terrains while traveling with fully-loaded touring bikes.
The inside of an internally geared hub’s large shell is a complex arrangement of gears that would amaze even the most skilled watchmaker. Explaining the intricate workings of these gears is challenging, and it is not necessary to delve into the details. Here’s a simplified explanation: the interlocking gear system within the hub consists of “planetary gears” that revolve around a central “sun gear” attached to the axle. When a rider pedals, power is transferred to the rear hub through a drive system resembling a single speed drivetrain, with a sprocket at the cranks and a primary cog mounted on the rear wheel. However, as the power reaches the rear cog, it passes through a transmission-like system of gears within the hub, resulting in various gear ratios. These gears either amplify the pedaling force to increase wheel speed or reduce it to slow down the wheel.
Internally-geared hubs received little attention in the mainstream cycling world, myself included. That is, until e-bikes disrupted the definition of mainstream.
Suddenly, the market was flooded with newcomers to cycling, searching for e-bikes that were user-friendly. They desired a mode of transportation to easily commute to the store or work, requiring minimal maintenance and no prior knowledge of shifting techniques (which is indeed important). Additionally, they wanted bikes that would provide lasting performance.
E-bikes presented a new mechanical challenge for traditional drivetrains: they generated significant force. Not only did the powerful motors risk stretching chains and wearing out cassettes faster, but the lateral forces of shifting multiple gears simultaneously and “cross-chaining” became greater concerns.
**Internally Geared Hubs: A Solution to Mechanical Problems**
Internally geared hubs provide a convenient solution to two mechanical challenges. These hubs have the remarkable ability to withstand wear over time and shift seamlessly under heavy loads. For novice cyclists, they offer a user-friendly experience as you can effortlessly shift gears while pedaling uphill or even when stopped. Once installed and properly tuned, there is little room for error.
Currently, the market offers only a limited number of options when it comes to internally-geared hubs. However, both entry-level cyclists and experts can still find quality choices. Shimano manufactures the reliable and budget-friendly Alfine and Nexus hubs, which come pre-installed on various commuter, cruiser, and cargo e-bikes. Another option is the less common English-made Sturmey Archer hubs, particularly popular in the U.S. For those seeking a high-end internal hub experience, the German manufacturer Rohloff offers the 14 gear SPEEDHUB, highly favored by e-bike enthusiasts and long-distance tourers.
Enviolo (formerly known as Nuvinci) presents a unique approach to internally-geared hubs with its stepless drive system. Instead of incorporating a fixed number of gears, Enviolo employs an innovative arrangement of rotating balls and rings that allow for a continuously variable bicycle transmission. In essence, it follows the same principle as the aforementioned geared systems, but with the notable difference that there are no predetermined gears to select from. Instead, you simply twist the shifter, and the gear ratio adjusts accordingly.
Despite the rising prominence of internally-geared hubs in the cycling world, particularly with the increasing popularity of e-bikes, the traditional drivetrain remains supreme.
The Importance of Robust Drivetrains on E-bikes
In response to concerns about accelerated wear and tear on e-bike drivetrain components, mainstream bicycle component manufacturers implemented a simple yet effective solution – strengthening and refining the entire system.
Enter SRAM, the American component company that fully embraced this concept with the launch of their EX1 eMTB drivetrain group in mid-2016. The EX1 cassette is precision-engineered using tool-hardened steel for enhanced durability, while the chain is larger and more robust. SRAM has also restricted the EX1 shifter to single gear shifts, departing from their standard shifters that allow for multiple gear shifts simultaneously. According to SRAM, this approach prolongs battery life and mitigates potential component wear.
While the EX1 remains the sole dedicated e-bike drivetrain from SRAM, the company has implemented its single-shift concept throughout most of its MTB shifters. These shifters come in two versions: the standard shifter, capable of executing multiple shifts simultaneously, and the e-bike version, which allows for only one shift at a time. This enables eMTB riders to utilize a regular SRAM groupset while still benefiting from some protection against increased wear and tear.
SRAM takes a highly customizable approach to their drivetrains, allowing for easy mixing and matching of various components. Their “Eagle” lineup of drivetrain components is fully compatible with one another.
So, which drivetrain should you choose for your e-bike?
The cycling world offers an abundance of drivetrain options, which can make decision-making overwhelming if you’re unsure of your preferences.
As mentioned in Electric Bike Report’s guide to buying your first e-bike, the answer to this question should guide you in choosing the right drivetrain: What do you intend to do with the bike?
If you’re someone who hasn’t ridden a bike in years and prefers minimal shifting, an internally geared hub might be the ideal choice. These hubs are remarkably user-friendly and forgiving, allowing you to shift while stationary or under load. Additionally, they require very little maintenance compared to their traditional counterparts, which need frequent lubrication and cleaning.
On the other hand, if you’re already accustomed to a traditional bicycle drivetrain, sticking with that option may be more preferable. Our experienced testers overwhelmingly gravitate towards e-bikes equipped with a sprocket, chain, and cassette drivetrain. Personally, I find the ride to be sportier and more reliant on my input (in a positive way). The only drawback is that these drivetrains demand regular maintenance to operate smoothly.
Operating on a budget? Single-speed e-bikes are incredibly enjoyable and provide an affordable entry point without breaking the bank. Don’t be daunted by the absence of gears (that’s what the motor is for), but be aware that you might feel the hills more compared to bikes with gear options. The simplicity and user-friendliness of single speeds hold a special place in my heart, which is why e-bikes with one gear, like the Rad Power Bikes RadMission1, are my go-to cruisers for bike paths.
Remember, whichever option you choose, none of these systems are flawless and will require occasional maintenance. Your local bike shop can be your ally here. Build a relationship with them, trust their expertise, and if you encounter any issues with shifting or peculiar sounds, take your bike to them.