BrakesSpoon

Ebike Braking Essentials and Ebrakes

March 7, 2016
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There comes a time in every ebiker’s life where braking becomes a high priority, especially in a world filled with inattentive car drivers that so often do not even notice fast moving bicyclists. A car may pull out right in front of you, or open a door in front of you as you ride in a bike lane, and countless other obstacles.

In emergencies like these even a small improvement in stopping power can make a big difference, especially if you are riding an electric bike with its higher speed and increased weight. While good equipment like disc brakes are highly recommended, this article focuses on the basic information to use the brakes you have most effectively.

[the pic at this articles’ header is a “spoon brake” on a bicycle from the 1890’s]

Braking Dynamics

If you try braking hard at high speed using only the rear you will likely notice skidding. The reason behind this is one of the keys to understanding how to make the best use of your brakes.

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In this picture a bike’s brake has been applied hard enough that the rear completely lifts up off the ground. This is due to inertial force causing a ‘load transfer’, where your bike and the load on it wants to keep moving forward which shifts the load toward the front when braking. This can greatly reduce or completely eliminate the effectiveness of the rear brake the greater the speed, since as the load on the rear is reduced so is its traction, until you reach the point where the rear may no longer even contact the ground.

The rear wheel may stop rotating with good brakes, but with a reduced load on the rear it will mostly result in the aforementioned skidding. This is known as wheel lock, and it reduces both the braking effectiveness and control you have on the bike. The same does not happen with the front brakes, in fact its effectiveness is improved due to more weight being on the front.

Therefore the conventional wisdom is that you use the front brake the most, except in low traction conditions where the front may skid. If the front locks up in slippery conditions you will certainly crash due to total loss of control, so the rear brake must be used. In other words, low traction conditions call for the low traction brake. Load transfer, and therefore how much you depend on the front brake, also depends on the type of bike and where the load is placed. Additionally the overall amount of braking should be less in slippery conditions and turns regardless of which brake is used in order to maintain control.

While many bicyclists prefer to use mostly the front in regular conditions, the rear still provides some braking power if needed and can be used in a ratio primarily favoring the front brake for maximum stopping power, as shown in this motorcycle braking video which provides a comparison of braking distance for each method.

Considerations for E-bike Builders

Another important concept is to keep heavy items low and centered between the two wheels. The higher you have heavy items above the wheels, the greater the load transfer when braking. In extreme circumstances this could cause the bike to flip over if braking hard enough. Conversely the lower something is on the bike the less the load transfer. This is particularly an issue to consider in the case of a heavy item like an ebike battery pack, where you have several potential mounting options including front, rear, center and carried in a backpack.

Ideally we would keep this situated low in the center triangle to maintain the dynamics of the bike as much as possible. One of the reasons why Tesla electric cars handle so well is their approach to this same concept, keeping the battery pack as low and centered as possible by placing it in the area underneath the passenger cabin typically occupied by a car’s exhaust system.

Rear brake effectiveness may actually be improved in the case of putting a hub and battery in the rear since the increased rear weight would help increase the tire’s contact with the ground in emergency braking. However, it would also reduce the amount of traction your front tire gets when emergency braking due to a lower than usual load transfer, since the rear wheel is weighted down and prevents the bike from pitching forward. Therefore the bike frame also plays a critical role in the optimal ratio of front to rear brake use.

For example a cruiser is low and long with a center of gravity more towards the rear, reducing the load transfer that would normally take place, and increasing the need to brake with the rear. Adding more weight to the rear would exaggerate these changes in the bike dynamics. Not necessarily a bad thing but it could require more practice to successfully manage an emergency stop without crashing.

The takeaway from all this is that as much as possible we want balance between the two wheels and a low center of gravity. The gold standard is a mid drive motor and center mounted battery on a mountain bike, this build best maintains the handling and braking of a bike.

E-brakes, with a power cut-off

When building an ebike make sure to install ebrakes. Ebrakes are an essential part of your system and cannot be overemphasized enough, as they cut power to the motor (or also engage the regen braking when you pull the lever, if you have a direct drive hubmotor). Most factory built bikes include this as standard, as do many kits.

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For anyone who does not think ebrakes are necessary in an ebike look at this video out of China as a clear illustration why ebrakes are a good idea:

One big fear for an ebike builder is that their throttle gets locked in wide open throttle position (WOT) as happened to the woman in the video. This can sometimes happen if moisture shorts the internal wires (read our article on water-proofing your ebike here). The ebrake can be a safeguard that will from keep this from happening.

Generally the more powerful the motor on your ebike, the more needed ebrakes are. If you are confident your brakes are more powerful than the motor , and your brakes are strong enough to easily lock the rear wheel if the throttle gets stuck in wide open throttle…then you may be able to argue against ebrakes.  For example if you all you have is a 250 watt geared hub motor and you have hydraulic disc brakes properly adjusted…you really have no need for ebrakes. If you have a Cyclone kit 3000 watts and you got it over-volted to 7000 watts …going without ebrakes would be considered hazardous.

Ebrake Options

If you want to upgrade your current brakes to a cable-operated Avid BB7 caliper, or you want to upgrade your brakes to hydraulic (either just the front brakes, or both the front and rear), the Luna Cycles web-store carries a selection of well-regarded Avid and Shimano brake products.

If you find that your discs and pads are getting very hot from frequent heavy braking, you might consider upgrading to a larger diameter disc on the front. This will allow you to have the same braking power with less pressure on the pads and discs, plus it will provide more disc material mass to absorb and shed heat. Doing that will require a larger diameter disc, and also a caliper mount position adapter]

Tektro is the most reputable for making quality hydraulic ebrakes that are also affordable. As you will find out adapting hydraulic brakes is the only hard type of brake to convert (because of fluid filled brake lines) of any type of ebrake.

Alternatively you can get ebrake sensors that use various technologies to sense when you pull the handle even with hydraulic brakes.

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Most kits come with e-brake handles that work well with mechanical type brakes but they are generally cheap and chinese looking. If you have fancy expensive brake handles you might decide  to use a sensor instead and toss your kit e-brake handles.

How to Install Ebrakes

Read our guide on different install option and how to install them on the bafang mid drives for clues on how to go about installing ebrakes on an existing set up.

Conclusions

As you can see there are many things to think about when determining how best to use the brakes on your ebike, and it will vary depending on what you have. Take a long look at your bike, how the weight is distributed and consider the intended terrain. Above all, practice emergency braking before you need to, so you have some idea of how your bike will handle. Use varying speeds, try front and rear, different inclines and road conditions. In the end, it just might save you from a crash.

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Written by Gary Whetstone, March 2016

[editors notes: the cables in common cable-operated brakes have a tiny amount of “stretch” in them when actuated, and some builders prefer to eliminate that sponginess by upgrading to hydraulic brakes. Also, hydraulic brakes automatically adjust the pads to compensate for pad wear, up to the point when the pads need to be replaced.

The Avid BB7 cable-operated calipers provide a knob on the caliper to adjust for this pad wear, so no tools are needed to do that when you notice the pads have worn some, and do not grab as hard as before.

If you want to upgrade your current brakes to a cable-operated Avid BB7 caliper, or you want to upgrade your brakes to hydraulic (either just the front brakes, or both the front and rear), the Luna Cycles web-store carries a selection of well-regarded Avid and Shimano brake products.

If you find that your discs and pads are getting very hot from frequent heavy braking, you might consider upgrading to a larger diameter disc on the front. This will allow you to have the same braking power with less pressure on the pads and discs, plus it will provide more disc material mass to absorb and shed heat. Doing that will require a larger diameter disc, and also a caliper mount position adapter]

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Edit on March 20, 2016

Thanks to a recommendation from squeakypeep@gmail.com, I would like to add a tip. If you don’t have a favorite “upgrade” brake system, I recommend looking into the Tektro Dorado front brake hydraulic system. If you only upgrade the front brake to hydraulic, the cost (roughly $120) isn’t horribly bad. It comes with a 203mm diameter disc that is a robust 2.3mm thick. It has an E-brake interface, so applying this brake will actuate the controllers power-cutoff (for as long as the brakes are applied).

Depending on how much weight and speed your ebike experiences, a lightly-loaded ebike can get pretty good performance from Kool Stop Salmon pads in the stock rim V-brake system. If you want a disc brake on the rear (or simply have a rear disc bicycle that has a weak stock disc system), a cable-operated (instead of hydraulic) disc that upgrades a common 160mm disc to 180mm and also swaps the caliper to the well-known Avid BB7‘s is often enough of an upgrade to satisfy most needs. They do not require any tools to adjust the pads for wear.

Nothing wrong with going to hydraulic on the rear, too, but…for most riders, the extra expense of a rear hydraulic system is not required.


  • jonthezombie

    I bought the BBSHD kit…..and unfortunatley the ebrake magnets don’t fit on my hydraulic brakes. Even if they did, I don’t really enjoy how they work, I would prefer something more instant when it comes to braking. For now I have my setup as throttle only, but I will be looking at the different options out there and buying a new front handle soon.

    • passerby

      You might want to look at the Tektro Dorado hydralic ebrake kit. Empowered cycles has them. It replaces the whole brake mechanism, levers, even the rotor with more beefy stuff built for ebikes and the ebrake is built into it in a way you won’t get with any other hydraulic option. Even got an ebrake connector for the BBSHD so it is plug and play.

    • Scott Mac

      I had the same problem trying to install brake cut offs on hydraulic brakes . Even the installation video on how to install them on hydraulic brakes on youtube shows the guy installing them on manual brakes . Probably because they don’t work on hydraulic brakes . That was a waste of 20.00 bucks.

      • BobTrost

        I mounted mine with electrical tape and they work fine, ugly but work.

    • René

      Hello jonthezombie,

      This is my solution, and I am happy with it.
      check the pictures

      René

  • Elhanan Maayan

    I’m curious to know the recommended breaking distance for various speeds on ebikes

  • v3ngence

    Good info, I got the Cyclone kit from Luna and it’s a blast, just make sure to install those ebrakes! I ziptied the magnet to the lever, and the sensor to the body of my brakes, then glued over the top of both to make it extra secure. For the cyclone it works great and is an instant cut-off, but just remember to let go of the throttle before you let go of the ebrake!
    I also changed out my front v-brake for a BB7 disc, stopping quickly over 30mph was too much even for koolstop salmons!

  • roadkill612

    I hear 2 things.

    1/ regen will always result in some drag compared to freewheel

    &2/ the energy dump cant really be absorbed effectively as charge anyway. If the bike had a little capacitor to absorb the dumps, maybe.

    seems to me if you use the brakes a lot, you are doing something wrong.

  • suraj panchal

    I have ganarate a new one wheel bycycle ….it is electric unicycles …my query is what types brake I use pls tell some guide….???and that types cycle balancing is available????