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What You Need to Understand About E-bike Brakes
The kill switch and its crucial role in e-bike brakes
E-bike brakes come in various types, but what distinguishes an e-bike specific brake and makes it an essential safety feature is a straightforward electronic or mechanical switch that is installed on the lever. This switch detects even the slightest application of the brakes.
This switch, referred to as the kill switch, immediately cuts off the power supply to the motor when the brakes are applied. This safety feature is especially vital on high-powered Class 3 e-bikes capable of reaching speeds of 28 mph, as well as on Class 2 e-bikes with throttle control. Without the presence of a kill switch, a rider could unintentionally activate both the brakes and the throttle simultaneously. Moreover, it serves as a valuable failsafe in the event of a controller failure or a stuck throttle, where a kill switch becomes crucial to bring the bike to a stop without further damaging the motor.
Brakes designed for e-bikes may incorporate other considerations, such as thicker brake pads and rotors to effectively handle greater stopping forces. Some even have specialized designs to accommodate unconventional e-cargo bikes. However, it is the kill switch that sets them apart from brakes intended for traditional bicycles.
Concerns regarding a rider accidentally engaging both the brakes and throttle simultaneously may initially seem exaggerated within the bike industry. However, it is a realistic scenario, particularly for inexperienced or new riders who may become unpredictable in emergency situations or crowded areas. It cannot be assumed that an individual will possess the muscle memory required to release the throttle in a split second before colliding with an object or person. Furthermore, the immense power of most Class 3 e-bikes, with a 750w motor at full capacity, can quickly spiral out of control. In such cases, a brake lever kill switch serves as a valuable tool for maintaining control over the bike.
When it comes to e-bike specific brakes, Tektro is undoubtedly the largest manufacturer, offering at least 17 different setups equipped with a kill switch. Other prominent brake manufacturers, like Magura, TRP, and SRAM, also produce brakes designed specifically for e-bikes. It is worth noting, however, that not all of these options incorporate a kill switch but instead focus on enhanced durability to accommodate the increased power and weight of e-bikes.
These additional safety features play a crucial role in the high-powered e-bikes commonly seen on roads and trails today. Nevertheless, it is important to recognize that not all e-bikes come equipped with brakes specifically tailored to their requirements.
Having high-power brakes and an automatic motor shut off provides the utmost safety on e-bikes
Tektro brakes are among the most prevalent on bicycles.
Regenerative Braking: Why Isn’t It More Popular on E-bikes?
While electric cars possess technology capable of recovering energy during braking, regenerative braking remains relatively uncommon in the world of e-bikes.
There are indeed a handful of e-bikes that incorporate regenerative braking, but they are far from being mainstream. Numerous reasons contribute to this lack of popularity, but the simplest explanation lies in the fact that these systems are not particularly efficient at recovering energy. It is important to note that this inefficiency does not stem from subpar technology but rather from the nature of cycling itself.
Regenerative Braking: Harnessing Power on Bicycles
As the name implies, regenerative braking on bicycles requires riders to engage the brakes, allowing the system to recover energy. However, unlike electric cars, braking on bicycles is typically brief. Cyclists often choose to coast and gain speed while going downhill instead of applying brakes. While the opportunity for regenerative braking exists, it is less likely to be utilized compared to cars where factors like speed limits and traffic encourage drivers to brake more frequently on descents.
Limitations of Regenerative Braking
Regenerative braking in bicycles is limited to a specific type of hub motor and cannot be easily implemented in mid-drive e-bike systems.
Notable Brands of E-Bike Brakes
If you own a bike with a brake-operated kill switch, there’s a good chance that your brakes are manufactured by Tektro.
Other major bicycle brake manufacturers such as SRAM and Magura have also joined the e-bike brake market, each offering their own versions. However, Tektro stands out for fully embracing the motorized trend and providing a wide range of affordable, practical brakes. Many bike brands choose Tektro brakes, which are equipped with a kill switch, as the default option.
The variety of Tektro brakes on our test bikes is extensive, prompting us to create a handy chart for reference. This chart also helps in identifying where a particular brake model stands within Tektro’s lineup.
TRP, Tektro’s performance brake brand, offers its own range of e-bike brakes and collaborates with esteemed companies like Stromer and Riese & Müller to create customized systems for their e-bikes.
Tektro brakes are featured on numerous e-bikes from different brands.
German manufacturer Magura also produces e-bike brakes, featuring a kill switch across their three available models. Their hydraulic rim brakes have a distinctive appearance reminiscent of headphones.
SRAM, a renowned bike component manufacturer, offers a brake specifically designed for eMTBs. While lacking a kill switch, the SRAM Guide RE brake incorporates a four-piston caliper derived from their downhill racing brakes. This larger caliper, combined with the trail-oriented Guide lever, enhances the brake’s ability to handle higher potential speeds and increased weight of electric mountain bikes.
As parts become increasingly difficult to find, newer brands like Nutt and Zoom brakes have emerged as potential substitutes for well-known brake manufacturers. We have tested many of these alternatives on the e-bikes we’ve reviewed and, so far, they have proven to be reliable. Only time will determine the longevity of these brands, though.
Interestingly, Shimano, the prominent bicycle component giant, does not produce e-bike specific braking systems. However, many high-end e-bikes still utilize Shimano brakes without the specific features tailored to e-bikes.
Considerations for E-Bike Brakes
While e-bike specific brakes are not always necessary, it is important to approach alternative options with caution.
Exploring Sportier E-bikes and Braking Systems
When delving into sportier e-bikes, as well as Class 1 and Class 3 bikes without a throttle, you’ll come across numerous models equipped with traditional braking systems that lack a brake-activated kill switch. This is a common and safe occurrence, especially among higher-end traditional bike manufacturers producing eMTBs, electric road bikes, and stealthy commuter e-bikes.
On these pedal-assist only bikes, the motor is supposed to automatically deactivate once you stop pedaling. However, the keyword here is “should.”
The Role of Pedelecs and Sensor Technology
In a pedelec, a cadence or speed sensor located on the bottom bracket instructs the motor to cease propelling when you stop pedaling. Ideally, the power should halt immediately after ceasing to turn the cranks. In practice, however, there is occasionally a delay.
The presence or absence of this delay depends on the quality and calibration of the e-bike’s cadence sensor. Without a brake kill switch, the bike solely relies on the sensor to signal the motor to cease running once you begin coasting. Many cadence sensors are positioned in a specific segment of a pedal stroke, let’s say at 12 o’clock, for instance. If you stop pedaling at 6 o’clock, the bike’s cadence sensor might not detect the coasting until half a pedal stroke later, resulting in a delay.
To clarify, a brief delay between ceasing to pedal and the motor shutting off is not indicative of a cheap or unsafe e-bike. For example, the Evelo Delta X, a bike I currently enjoy riding at the Electric Bike Report offices, keeps the power on for a fraction of a second after pedaling stops. While it is noticeable to me, it is so short that most individuals on our staff do not perceive the delay. The bike, priced at $3,699, is far from being cheap or unsafe and provides a thrilling riding experience.
The Role of Brakes in E-bikes
Interestingly, both Shimano and SRAM, the world’s two largest and most renowned bike component manufacturers, do not produce a brake system with an integrated kill switch. Their brakes are commonly found on high-end performance e-bikes, where the cadence and torque sensors are meticulously calibrated to replicate the natural pedaling sensation.
The lesson here is that while e-bike specific brakes with a kill switch are not necessarily obligatory for pedelecs or speed pedelecs, they are undeniably beneficial. They provide a failsafe in case of any malfunction and enhance your control over a pedal-assist e-bike. On the contrary, it is never advisable to ride a Class 2 bike without a brake-controlled kill switch.
Additional Insights on E-bike Brakes
It is worth noting that e-bikes like Rad Power Bikes’ RadWagon 4, being heavier than typical bicycles, require more robust stopping power.
While mechanical disc brakes may not possess the same stopping capabilities as hydraulic brakes, they offer a more affordable alternative.
E-bike brake systems extend beyond being mere kill switches, or the lack thereof.
First and foremost, the brakes on your bicycle must excel at the obvious task – slowing you down. The substantial weight, power, and high speeds of modern e-bikes make this an even more significant responsibility than one would presume. Consequently, I contend that the quality of your e-bike’s brakes takes precedence over all other considerations. After all, what good is the ability to ride at high speeds if you cannot decelerate safely?
Disc brakes, irrespective of whether they are specifically designed for e-bikes or not, should be regarded as obligatory equipment for any type of e-bike. Period. E-bikes are simply too heavy and powerful to utilize traditional bicycle brake designs like rim brakes or cantilevers; hence, disc brakes are the optimal solution. The industry has largely accepted this viewpoint, leaving no excuse for selecting a bike that does not come equipped with a disc brake setup.
Numerous e-bikes are equipped with brake systems resembling those found on almost any standard non-motorized bicycle, particularly mountain bikes and flat-bar style bikes. This is perfectly acceptable, even if they lack a kill switch mechanism.
Therefore, here are a few factors to bear in mind when evaluating a bike’s brake setup:
As a general rule, hydraulic disc brakes outperform cable-operated mechanical disc brakes, although the latter are more cost-effective and still perform adequately. In hydraulic setups, it is possible to find brakes with four pistons per caliper instead of the standard two, which is typically seen on higher-end or heavier e-bikes. Some manufacturers, such as SRAM and Tektro, have also experimented with increasing the thickness of their disc brake rotors and pads on e-bike-specific braking systems, claiming to enhance braking power and durability.
Setting aside all of the aforementioned considerations, if there is one key point to remember from this article, it is this: the larger the brake rotor, the more formidable your braking capabilities become. While this statement oversimplifies matters slightly, it is not incorrect.
A larger brake rotor accomplishes two things. Firstly, it facilitates better dissipation and storage of heat, resulting in increased stopping power. Secondly, it augments the amount of braking torque, which, you guessed it, translates into greater stopping power. However, this does not imply that individuals should attach pizza pan-sized discs to their e-bikes (although if you do, I would love to see pictures). The size of your brake rotor should be proportionate to the dimensions, weight, and speed of your e-bike.
The largest rotors observed on e-bikes typically reach a maximum size of around 203mm, while a standard size that feels secure and comfortable on most e-bikes is 180mm. For a typical full-size e-bike, the minimum rotor size we recommend is approximately 160mm, although some lightweight and moderately powered folding bikes, like the Gocycle GX, are adequately served by smaller rotors. Again, the rotor size is always relative to the bike’s size, weight, and power.
Personally, I prefer to err on the side of larger rotors. In the environs of southwest Utah, where Electric Bike Report is based, we predominantly ride heavier, more potent Class 3 speed pedelecs since we often need to cover vast distances swiftly (given the sprawling nature of the region). Bike paths and lanes form the backbone of our cycling routes, and I desire a brake system that instills confidence and control, capable of handling unexpected encounters with children darting onto the path or cars encroaching into my lane.