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Guide To Electric Bike Brakes
May 18, 2022
What You Should Know About E-bike Brakes
There are lots of companies hyping products that claim to be made specifically for e-bikes.
You can buy e-bike drivetrains, e-bike rated tires and even e-bike rated cycling shoes — It seems like everyone is trying to get in on the electric bike boom.
E-bike braking systems are high on the list of components we see most often marked as e-bike specific. A quick survey of the dozens of e-bikes currently in the Electric Bike Report offices shows they are all equipped with a braking system made and marketed specifically for e-bikes.
So, should you buy into the hype around e-bike brakes? Yes. You absolutely should. But there are some things to take into consideration.
The kill switch, and why it makes e-bike brakes so important
They come in many variations, but the hallmark of an e-bike specific brake (and why they are such an important safety feature) is a simple electronic or mechanical switch mounted on the lever that detects when you apply the brakes, even slightly.
This switch, known as the kill switch, cuts power to the motor immediately when you apply the brakes. This safety feature is particularly important on the ultra-powerful Class 3 e-bikes capable of 28 mph and on Class 2 throttle-controlled e-bikes, where, without a kill switch, a user could inadvertently apply the brakes and throttle at the same time. It’s also a good failsafe should your bike’s controller fail or throttle stick open, where without a killswitch you’re along for the ride until the battery dies or you force the bike to stop and risk burning out the motor.
You’ll likely see other design considerations on brakes made for e-bikes, such as thicker brake pads and rotors to handle greater stopping forces or even special designs for quirky e-cargo bikes, but the kill switch is what sets them apart from brakes made for traditional bikes.
Concern over a person jamming on the brakes and throttle at the same time may seem like some bike industry pearl-clutching, but it’s not far-fetched. Riders of all skill levels — but particularly the new or inexperienced — can get unpredictable in emergency situations or in crowded areas. You can’t just assume a person will have the muscle memory to untwist the throttle when they have to stop in a split second before hitting someone or something. It’s also hard to understate the sheer power of most Class 3 e-bikes — a 750w motor at full power can get away from you quickly, and a brake lever kill switch can be a useful tool in keeping the bike under control.
Tektro by far is the largest maker of e-bike specific brakes, with at least 17 variations of kill switch-equipped setups. Other major brake manufacturers like Magura, TRP and SRAM also make brakes designed with e-bikes in mind, though it’s worth noting some don’t feature a kill switch and are instead beefed up to handle the increased power and weight.
These additional safety features are important on the ultra-powerful e-bikes we see on roads and trails today. But not all e-bikes come with brakes built specifically for them.
Having high power brakes and motor shut off keeps you safest on e-bikes
Tektro brakes are among the most common you find on bikes.
Regenerative braking: Why isn’t it more popular on e-bikes?
Electric cars have technology that can recoup energy during braking, so why don’t more e-bikes do the same?
You can find a handful of e-bikes equipped with regenerative braking, but they’re by no means common. There’s lots of reasons for why that’s the case, but the simplest explanation is that the systems are not particularly efficient at recovering energy — not because the technology is bad, but because of the way bicycles are ridden.
As the name suggests, regenerative braking requires a bike’s user to apply the brakes in order for the system to recoup power. But braking on a bicycle is very brief compared to an electric car. Bicycle riders, for example, are more likely to stay off the brakes and coast when going downhill in order to gain speed. The opportunity for regenerative braking is there, but it’s less likely to be taken advantage of than if you are in a car, where things like speed limits and traffic make it more likely that a driver drags the brake going downhill.
Regenerative braking is also limited to a specific type of hub motor, and cannot be easily applied to mid-drive e-bike systems.
Not a ton of brands make e-bike specific brakes
If you’ve got a bike equipped with a brake-operated kill switch, odds are good those brakes are made by Tektro.
Other big bicycle brake manufacturers like SRAM and Magura have also jumped in with their own version of e-bike brakes, but Tektro has notably embraced the motorized trend and offers an extensive lineup. They’re affordable, utilitarian and almost universally equipped with a kill switch, so many, many bike brands spec their bikes with Tektro brakes.
We see lots (and lots) of different Tektro brakes on our test bikes. So many that we made a nifty chart to help us keep track of them. It also gives you an idea of where a specific brake sits in their lineup:
Tektro’s performance brake brand, TRP, makes its own variations of e-bike brakes and has partnered with high-end companies like Stromer and Riese & Müller to make custom systems for their e-bikes.
Tektro make brakes that are featured on many different e-bikes
SRAM, one of the most recognizable bike component makers, also makes a brake specifically for eMTBs. While it lacks a kill switch, SRAM’s Guide RE brake utilizes a four-piston caliper derived from the company’s downhill racing brakes. The larger caliper combined with the trail-oriented Guide lever makes for a brake better capable of handling the higher potential speeds and increased mass of electric mountain bikes.
Over the last year or so as parts have become increasingly harder to find, newer brands like Nutt and Zoom brakes have been seen more and more as substitutes for some of the better known names in brakes. We’ve tested many of these on e-bikes we’ve reviewed, and so far they are holding up pretty well. Time will tell what the longevity is on these brands though.
A company that’s noticeably missing from the list of e-bike brake manufacturers is Shimano. The bicycle component giant does not make an e-bike specific braking system, though you do see many higher end e-bikes running their brakes without any of the e-bike specific features.
You don’t always need e-bike specific brakes, but be weary
Dive into the world of sportier e-bikes, or some Class 1 and Class 3 bikes with no throttle, and you’re going to find lots of bikes running traditional braking systems that lack a brake-activated kill switch.
This is safe and normal, and is particularly common on eMTBs, electric road bikes and stealthy commuter e-bikes made by higher-end traditional bike manufacturers. On these bikes, which are typically pedal assist only, the motor should automatically shut off when you stop pedaling.
The key word here being “should.”
On a pedelec, a cadence or speed sensor mounted on the bottom bracket tells the motor to stop pushing when you stop pedaling. This stoppage of power, in theory, should be immediate after you stop turning the cranks. In practice, there’s sometimes a lag.
The cause of this lag (or the lack of it on nicer bikes) is the quality and tuning of an e-bike’s cadence sensor. Without a kill switch on the brakes, the bike is entirely relying on that sensor to tell the motor to stop running after you start coasting. Many cadence sensors are mounted in one specific part of a crank’s revolution, say, for example’s sake, at 12 o’clock of your pedal stroke. If you stop pedaling at 6 o’clock, that bike’s cadence sensor may not register that you’re coasting for an amount of time equal to half a pedal stroke, which makes for a lag.
To be clear, a small lag between when you stop pedaling and when the motor cuts off is not at all a sign of a cheap or unsafe e-bike. One bike I currently enjoy riding at the Electric Bike Report offices, the Evelo Delta X, keeps the power on for a fraction of a second after you stop pedaling. It’s so short, I’m one of the few people on our staff to notice the lag. But it’s there, and by no means is that $3,699 e-bike cheap, unsafe or anything but a total blast to ride.
Shimano and SRAM, the two largest and most well known bike component manufacturers in the world, don’t even make a brake system with an integrated kill switch. You most frequently see their brakes on high-end performance e-bikes where the cadence and torque sensors are carefully refined to replicate the feel of natural pedaling.
The lesson here is that e-bike specific brakes equipped with a kill switch are not necessarily a mandatory component on pedelecs or speed pedelecs, but they’re never a bad idea. They serve as a failsafe in the event something malfunctions and can help you better control a pedal-assist e-bike. On the other hand, you should never ride a Class 2 bike without a brake-controlled kill switch.
E-bikes like Rad Power Bikes’ RadWagon 4 are heavier bikes and require more stopping power than typical bikes
Mechanical disc brakes don’t typically have the stopping power of hydraulic brakes, but they are less expensive
Other things to know about e-bike brakes
E-bike brakes are more than just their kill switches, or lack thereof.
First and foremost, your bike’s brakes need to be very good at the obvious — slowing you down. The weight, power and top speeds of modern e-bikes make this a taller job than you’d expect, which is why I’d argue the quality of your e-bike’s brakes are paramount to all else. It doesn’t matter how fast you can go if you can’t safely slow down.
Disc brakes, whether they are e-bike specific or not, should be considered mandatory equipment on any sort of e-bike. Full stop. E-bikes are just too heavy and too powerful for more classic bicycle brake designs like rim brakes or cantilevers, so discs are the way to go. The industry has fallen in line with this belief, for the most part, so there’s really no excuse to choose a bike that doesn’t come stock with a disc brake setup.
Many, many e-bikes come with brake setups that you’d find on nearly any type of non-motorized bike (mostly mountain and flat-bar style bikes). This is fine, even if they lack some sort of kill switch mechanism.
So, here’s a few things to keep in mind when you’re looking at a bike’s brake setup:
Hydraulic disc brakes, as a rule of thumb, are better than the cable-operated mechanical disc brakes, though mechanical brakes are less expensive and will do the job just fine. On hydraulic setups, you can also find brakes that come with four pistons per caliper instead of the standard two, which you’ll typically see on some of the higher-end or heavier e-bikes. Some manufacturers like SRAM and Tektro have also experimented with increasing the thickness of their disc brake rotors and pads on e-bike specific braking systems, which they say increases braking power and durability.
All of the above considerations aside, if you remember one thing from this article it should be this: The larger the brake rotor, the more powerful your brakes will be. This is a bit of an oversimplification, but it’s not wrong.
A larger brake rotor is going to do two things. First, it is going to dissipate and store heat better, which will equate to more stopping power. And second, it will increase the amount of braking torque, which, you guessed it, equals more stopping power. This does not mean people should start welding pizza pan size discs on their e-bikes (but if you do, send me pictures). Your brake rotor should be relative to the size, weight and speed of your e-bike.
The largest rotors we see on e-bikes top out at around 203mm, and 180mm seems to be a standard on most e-bikes that feels really nice and safe. The minimum rotor size we like to see on a typical full-size e-bike is about 160mm, though some lightweight and modestly powered folding bikes like the Gocycle GX do just fine with smaller rotors. Again, it’s all relative to size, weight and power.
For me, I like to err on the bigger side. In Electric Bike Report’s home locale of southwest Utah we’re typically hopping on the heavier, more powerful Class 3 speed pedelecs because we usually need to cover a lot of ground quickly (things are spread out here). Bike paths and bike lanes are our bread and butter, and I want a brake that’s going to keep things nice and controlled if a small kid darts into the path or a car cuts into my lane.