Can You Buy A Seat Tube Motor? (Where to Purchase, Pitfalls)
Last night, I discovered an e-bike with a motor hidden inside the seat tube. I was mesmerized by how small the motor was and how it was able to provide so much assistance to the rider. I then wondered, “Can you buy a seat tube motor?”
As a general rule, you can buy a seat tube motor as long as you can find it in the market and are able to purchase it. Unfortunately, seat tube motors are not commonly produced by known manufacturers, so looking for a seller of a seat tube motor is quite difficult.
Some people want their electric bike to look like a regular bicycle. For example, suppose all the electric components of an eBike are installed inside the frame, seat post, or seat tube, hidden from view. In that case, an electric bike can appear to be a traditional bike. This article will dive into the seat tube motor, how it works, and how it makes e-bikes appear like conventional bikes.
Can you Buy a Seat Tube Motor?
You can buy a seat tube motor for your electric bike. However, since seat tube motors are not commonly used for electric bikes nowadays, it is difficult to find stores or shops that sell this type of motor.
What makes it even more challenging to find is the fact that the most well-known manufacturer of seat tube motors—Vivax- was closed and went entirely out of business in 2020.
Through our research, we’ve come across an e-bike brand that sells e-bikes with a Vivax seat tube motor kit. The e-bike company that we found is called goat bikes. We’ve reached out to them through the email address listed on their website, but we haven’t received a response back as of this writing.
However, through deeper research, we’ve found an online shop, taiwantrade.com, where you can buy a downtube and seat tube motors. The downtube and the seat tube motors they sell are made in Taiwan. You can check out the shop and request pricing here.
What Is a Seat Tube Motor?
A seat tube motor is a motor that is hidden or installed inside the seat tube or seat post of an electric bike. The seat tube motor is tiny (about 31.6 mm in diameter) and is not commonly used in electric bikes.
Almost all electric bikes are recognizable at first glance because of their noticeable battery and motor. The motor most commonly used in e-bikes are hub motors and mid-drive motors.
However, your electric bike is more likely to look like a regular bicycle with a seat tube motor installed. Since seat tube motors are small, they are also incredibly lightweight.
In most cases, a seat tube motor will fit inside a bike tube with a diameter of more than 31mm. The battery pack is usually concealed in a water bottle, saddlebag, or seat post.
Seat tube motors have on average 200-350 watts of power, though some of these seat tube motors have a power rating of up to 400 watts.
“Everybody recognizes that if you can make very efficient electric motors, you can make a quantum leap forward.”
-James Dyson
How a Hidden Electric Bike Motor Works?
As a whole, the hidden motor or seat tube motor is activated by a secret switch. When the switch is turned on, the bevel gear mounted to your e-bike crank axle is turned, which results in increased propulsion of your electric bike.
Typically, the simple switch which turns on and off a seat tube motor is concealed on the handlebar. Likewise, the battery pack is usually hidden in the seat post, saddlebag, or a water bottle. Additionally, the battery is connected to the motor via the electronic control unit.
The seat tube motor is hidden inside the seat tube and is connected to the crankshaft through an interlocking gear. A tiny pin holds the motor in place inside the electric bike frame.
So, when you turn the switch on and start to pedal, the motor will engage and provide you with a boost in your ride. The motor is not that powerful, but it still provides you with enough power to give a boost to your ride.
If you want to watch a video on how the hidden motor or seat tube motor works, feel free to watch the video below.
Things to Consider Before Installing a Seat Tube Motor
- E-bike’s seat tube diameter
- Motor power output
- Difficulty of installation
- Battery pack position
- Type of terrain your riding on
E-bike’s Seat Tube Diameter
Your electric bike seat tube diameter is the first thing you need to consider before buying a seat tube motor. If your e-bike’s seat tube diameter is too small, you will not be able to fit the seat tube motor inside.
Typically, the seat tube motor has a 30.9-31.6 mm diameter. So, ensure that you have the right seat tube diameter size before buying a seat tube motor to avoid wasting your money on something that won’t fit your bike.
Motor Power Output
A motor is one of the essential electric components of your e-bike. It provides the assistance you are looking for when riding your electric bike. So, it is always best to know how much power your motor can offer and compare that to how much power you actually need.
The seat tube motor is small, and as a result, it produces a smaller power output when compared to a hub or mid-drive motor.
So, if you are planning to buy a seat tube motor, keep in mind that it typically produces 200-350 watts of power. In some cases, the power output can range from as low as 100 watts to as high as 400 watts.
If you are looking for a motor that provides a higher power output, a seat tube motor might not be the best option for you.
Aside from that, e-bikes with seat tube motors are usually equipped with low-capacity battery packs. The lower the capacity of your battery is, the less time you will have to use the assistance of your seat motor.
Difficulty of Installation
As a general rule, seat tube motors are difficult to install since they are small. In addition, installing a seat tube motor requires proper knowledge and expertise. So, if you are planning to buy a seat tube motor, you might need to seek out professional installation help.
Battery Pack Position
Another thing that you might want to consider is the location of your battery pack. You can choose to mount it in a saddlebag, in a water bottle, or the seat post. Though choosing your electric bike battery pack location is not crucial, it is still best to consider your end objection and how hidden you want your battery pack to be.
Type of Terrain
It is also good to consider the type of terrain on which you will usually ride your e-bike. For example, since a seat tube motor does not provide a powerful boost, it might not be the best idea to climb steeper hills regularly.
When climbing steep inclines, you will find that you may have difficulty climbing or riding your e-bike and that you will rely more on your leg strength when pedaling.
Suppose you are into intense riding and climbing steep inclines. In scenarios like this, you need a motor that can provide at least 500 watts of power.
However, if you are more likely to ride on a flat surface in most situations, a seat tube motor could work fine for you.
Before buying this type of motor, you have to think critically and consider the points mentioned above.
Is Seat Tube Motor Considered Cheating?
As a whole, using a seat tube motor in the cycling world is considered cheating. This is because installing a seat tube motor can be considered motor doping. In cases of motor doping, a hidden motor is mounted inside the bike’s seat tube, which boosts riding propulsion.
If you are a racer, installing a seat tube motor in your bike is considered mechanical doping, a form of cheating. There have been multiple news stories circulating where a cyclist used a bike with a hidden seat tube motor. The racer can go faster for extended periods and potentially win more races when utilizing a seat tube motor. Motor or mechanical doping in the cycling world is highly unacceptable.
However, if you’re not using the seat tube motor in a race, then there is nothing wrong with it. Besides, seat tube motors are designed to make your e-bike look like a regular bicycle. Therefore, a seat tube motor works well if you are into city riding while keeping a low profile.
If you are looking for an e-bike that could provide you with incredible climbing power, you might want to consider choosing an e-bike with high torque. If climbing up high inclines is a priority for you, please check our article “Which e-bike has the best torque.” to find the best electric bike for you.
