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.

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.

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.

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.