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What is electric bicycle transmission system

The function of the variable speed system of an electric bicycle is to change the speed by changing the combination of the chain and different front and rear gears. The size of the front tooth disc and the size of the rear tooth disc determines the power of the electric bicycle when it rotates the pedal. The larger the anterior disc and the smaller the posterior disc, the more strenuous the kicking. The smaller the anterior disc and the larger the posterior disc, the more relaxed the foot pedal. According to the ability of different riders, the speed of the e-bike can be adjusted by adjusting the size of the front and rear wheel, or dealing with different sections and road conditions.


* Speed Section

Variable speed e-bikes have 18, 21, 24, 27 and 30 sections, and those with more sections are usually more expensive and more suitable for a variety of road conditions.

General electric bicycle variable speed several speed refers to ‘before the market tooth piece number x after the flywheel tooth piece number’, electric mountain bikes is usually the first 3 market, after the flywheel six, seven, eight, nine, ten speed, multiplied by 18, 21, 24, 27, 30 speed. Electric road bikes are special. They only have 14,16,18,20,22 gears.



*Tooth ratio

“Tooth ratio = front plate tooth number/rear flywheel tooth number”, basically, the transmission system of the gear and chain of the electric bicycle is to “convert the energy (horsepower) of the driver’s pedal into the torque of the tire”.

The “speed” is determined by the maximum tooth ratio (the maximum tooth slice of the front plate corresponds to the minimum tooth slice of the rear flywheel). For example, the maximum tooth ratio of a 27-speed electric mountain bike is “front 44T, rear 11T, tooth ratio = 4”. The driver will turn four times when he steps on the wheel once, but the torque of the wheel rim is the fastest, and the relative force that the rider steps on must be the largest to maintain the torque required to make the car move forward.

“Climb” with minimum tooth than before (the market minimum tooth after corresponding flywheel tooth largest pills), climbing a hill, the driver is not only to maintain the car forward, while also rising height, when the need to increase the torque, on the premise of maintaining the same trample turnover number, reduce tooth torque higher than that of a tire, such as general 27 for a minimum speed climbing car gear “before 22 t, after 34 t, gear ratio = 0.65”, the wheels to turn 0.65 drivers on one circle, so the driver’s manual into torque to lift the car for climbing.


It should be noted that when the road surface is wet and slippery, the high torque will cause the tire to skid, that is, when the torque is greater than the friction of the ground, it cannot advance. In addition, when the high torque climbs the slope, it may turn up the solitary wheel.



* Tooth number drop

In addition to the tooth ratio, another thing worth discussing is the tooth number drop. Often heard “teeth than dense” is that the number of teeth drop small. The difference in tooth count means the difference between a driver’s effort and a tyre’s torque when he changes gears. For a driver, it is important to suddenly apply too much force suddenly, and suddenly too light, which can lead to the feeling of stepping on the air. In both cases, it may hurt the knee and affect the control.



* Part rating

Interestingly, due to the high cost of parts, manufacturers often improve the material or quality of components, and appeal to “more efficient transmission”, “smoother operation”, “more durable” and “more beautiful” to make consumers more willing to pay the price.

Commercially available bike variable speed system, the market is a three, two, three, the flywheel is complex, from introduction to five or six speed to advanced the seven or eight of the nine or ten speed and professional, segments usually means that there may be more higher than the highest gear, lower the minimum gear ratio and the number of teeth on the smaller gap, so to cope with traffic more naturally. In the parts mechanism, eight speed flywheel upgrade to nine speed ten speed can be universal original flower drum, seven speed below the flywheel to upgrade will have to replace flower drum. On a bicycle, flower drum goes with the wheel set, so changing flower drum means changing the wheel set.



* The role of the transmission

The bicycle’s transmission, the front three tooth disc, the rear nine tooth disc combination may change speed 27. Take the mountain bike as an example.

When you rotate the pedal, the front teeth rotate, passing the power through the chain to the back teeth, and the wheels move forward. The size of the front tooth plate (number of teeth) and the size of the rear tooth plate (number of teeth) determine the strength of the pedal when rotating.

The larger the anterior disc, the smaller the posterior disc, and the harder it is to pedal.

The smaller the anterior disc and the larger the posterior disc, the easier it is to pedal.

Cycling starts, stops, uphill, downhill, windward, downwind, etc. No matter what conditions can maintain a certain speed (bicycle fast forward, or slow forward, can maintain a certain step speed and torque, the transmission.

If you do not increase their own strength, only increase gear ratio to ride quickly, it is impossible. I discovered this very quickly when I was actually riding. When riding with a higher gear ratio (high torque, low rotation), the most appropriate riding (the combination of torque and rotation that releases the most appropriate energy) is not achieved. This will increase the burden on the knee and become a cause of various disorders. (note: it’s best to ride at a constant pace, and the occasional fast or slow is a knee injury. If the time is short, I don’t care much, but if the time is long, all kinds of problems will appear.


With front and rear 2 disc brakes and 21-speed transmission system, you can choose any speed to complete your journey; To protect the motor,we have installed unique inductive power-off switch on Shimano brake, perfect brakes fully protect your safety.



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