How Long Do EMTB Motors Last?

A motor on an electric mountain bike has to deal with quite some abuse. They deliver a lot of power whilst being exposed to dirt and water often. As high quality as the most recent e-bike motors are, they have a certain lifespan. But how long do eMTB motors last and can they be repaired?

Based on research, the motor of an electric mountain bike will last around 10.000 miles (16.000 kilometers) when used with caution. The most common parts to fail on a motor are the the bearings. By not using the motors full potential constantly and properly cleaning and maintaining it, you’ll get the most out of it.

An electric mountain bike is quite expensive in purchasing and maintenance. It is good to know how long a motor will last so you know what to expect. In this article, we’ll look at mid-drive motors and discuss what parts might fail and when. We’ll even look at things you can do to keep your motor happy for as long as possible.

What Factors Determine How Long An EMTB Motor Will Last?

When looking at all the different types of e-bikes, an electric mountain bike gets more abuse than an electric city bike. It gets used in rough, steep and muddy terrain. The motor has to work hard constantly, whilst being attacked by water and dirt. Even though the product is designed to cope with these conditions, eventually the motor will fail.

The point at which this happens, is different for every mountain bike. There are three factors which determine how long an EMTB motor will last: design, usage and maintenance.

Design Of An E-Bike Motor

In principle, the concept of a mid-drive motor is fairly the same for most brands. It consists of an electric motor which through gearing (sometimes a belt) and a clutch, delivers power to the crankshaft. A few sensors and a circuit board regulate it all. In the picture below you see an exploded view of a Bosch mid-drive motor. All the parts are put into a casing which is water resistant up to a certain level. Consult the manual from the manufacturer to find out exactly what you should and shouldn’t do with you electric mountain bike.

We have to remind ourselves that E-bikes haven’t been around for that long. This means that the manufacturers are still learning and collecting data. There have been a few e-bike motors with a bad reputation, and there are stories of people which have had their motors replaced 4 times within the warranty period. This would cost the rider nothing since warranty should cover this, but still. During the past years, e-bike motors have improved massively and they will continue to do so. More on this in my article Are Electric Mountain Bike The Future?.

Other than doing good research on a motor and following the instructions from the manual, there’s not much you can do to affect the design of an e-bike motor. Sometimes it is better to buy a bike with a proven technology instead of getting a bike with the latest tech. Especially when it is your first electric mountain bike.

Usage Of An Electric Mountain Bike

Usage of course has a great influence on the lifespan of a motor. Having all this power at your disposal does mean that the components wear out quicker when you’re not careful. It’s is exactly the same as with your car; if you rag it all the time, you spend more time at the garage.

Where you use it has also a great influence on how long the motor lasts. Of course, lets not forget we are talking about mountain bikes. They are built for covering rough terrain and dealing with mud and water. The same goes for the electric variant; although they contain more delicate components, it won’t hurt them. But I wouldn’t advise you to be as hard on them as you would be on a regular bike. There are more cavities for water and dirt to sit which also makes it harder to clean. Riding in muddy conditions very often increases the chances of water or dirt entering the motor.

Although your manual explicitly tells you not to, derestricting your eMTB will not only shorten the motors life, you’ll also loose warranty if your bike is still in its warranty period. By derestricting you are not adding power, but you are increasing stress on the internal components. You are then using the power of the motor for a longer amount of time at higher speeds. More on derestricting in my article: Should You Derestrict Your Electric Mountain Bike?

Maintaining An EMTB Motor

Although an e-bike motor does not need preventive maintenance, there are a few thing you can do in taking care of it. Your motor will also benefit from you maintaining the rest of the components like the drive train. A smooth running bike means less resistance for the motor.

Don’t open up the motor within the warranty period when you suspect something’s wrong with it. The bolts are coated which makes it visible when they have been touched. Warranty becomes invalid immediately.

Talking about the motor specifically, the best way for you to maintain it, is to clean it regularly. You don’t have to be technically minded for this. Use a soft cleaning brush and a bucket with soap to remove all dirt from the motor and crank. Disassemble the motor guard every few cleaning sessions to remove any dirt buildup. You now also have the chance to clean the connectors. More on how to prevent water and dirt from entering your motor, you can find in my article: Can An Electric Mountain Bike Get Wet?

How Long Do EMTB Motors Last?

Motor manufacturers don’t give an indication about the lifespan of a motor. Presumably for the same reason why car manufacturers don’t tell what the longevity of the engine is. It really comes down to the factors as discussed in the previous paragraph. This makes it quite difficult to give a prediction.

Luckily, since electric mountain bike have gained a lot of popularity since 2018, there’s now quite some data on forums and from bike shops. I’ve gathered this data, and the average lifespan of the motor of an electric mountain bike is 10.000 miles or 16.000 kilometers. This is based on the experiences of bike mechanics and e-mtb users under average conditions. Under ‘average conditions’, we are talking about a bike which has been used and maintained in accordance to the manual. Motors that have been replaced prematurely due to a design or assembly fault (often within the warranty period), are an exception.

Around this mileage, parts of the motor may start to fail. It is worth mentioning that if you use the exact same motor in an electric road bike, the expected mileage is higher. Which parts are the first to fail and can they be replaced? We’ll discuss it in the next part of this article.

What Components Of An EMTB Motor Fail?

It is interesting to know what components actually fail. If you know what the weak points are and how they break, you can act on this and adjust your riding or maintaining style a bit. In this paragraph, we’ll talk about the components that fail due to mileage and age. We won’t be talking about components that fail within the first two years, as this is often due to a design fault and will be covered by warranty.

Bearings

Bearings are a very common part to fail on an ebike motor (and on a bike in general). This results in more noise, vibrations and resistance when pedaling. Mileage and dirt/water are the main culprit for a bearing failure. The bottom bracket bearings (or crank bearings) are the closest to the crank arms and are the most vulnerable. If water/dirt passes the seal, it is game over for the bearings (and other components eventually). In most cases, the crankshaft also gets corroded and needs replacing. You can recognize worn crank bearings by extensive noise and by excessive movement in your crank.

One-way clutch bearings are another common part to fail. The clutch makes it possible for you to stop pedaling whilst rolling and pedaling backwards. It’s responsible for (dis)connecting the motor from the crankshaft. There might be a problem with the clutch bearing when you feel that motor doesn’t disconnect after you stop pedaling and thus keeps pushing forwards. This will also often cause an error code on your control unit.

There are approximately 9 bearings within the motor unit that could potentially fail. Since the casing has to be opened up to replace for example the crank bearings, you might as well replace all bearings. A service kit from the manufacturer usually consists of all the bearings inside the motor.

Gearing

An electric motor needs a certain RPM to function optimal and deliver it’s maximum torque. This RPM is higher than the RPM or cadence at which you pedal (the RPM at the crank). Within the casing of the motor, are plastic and metal gears. They convert the RPM of the motor (±300 RPM) to a usable RPM to be able to assist you when pedaling at 60-90 RPM.

Part of the gearing is made out of a wear-resistant plastic. Although it is not a common part to fail, the teeth of the gears will wear and can break off. This can seize up the motor. Aggressive riding will accelerate the wear of these parts.

The symptoms of worn gearing are quite obvious; there’s no power delivery at all, or it’s intermittent. It will also cause an error code on your display.

Belt

Some mid-drive motors like the ones from Brose, use a belt belt/gear combination to drive the crankshaft. You can see an example in the picture below. The belt itself is a wear part and needs replacing periodically (9300 km or 15.000 miles). If it snaps, there is no longer any assistance from the motor.

Circuit board (PCB)

The circuit board within the casing is the brain of your e-bike. When you switch from Eco to Turbo on your control unit, it is the PCB that controls your motor.

Circuit boards can fail over time because of short circuit. The cause of this can be harsh riding which, but water is its biggest enemy. If the PCB was to fail, it will throw an error code on your control unit and the motor will stop working or only runs in limp mode. The dealer can read out the fault code.

Fault codes do not mean a failed PCB by definition. There are loads of other faults that may be detected by the sensors within the unit which result in an error code.

Can An EMTB Motor Be Repaired?

Online there’s a lot to be read about electric mountain bikes that have had their motor replaced. This might give the impression that when there’s something wrong with the motor, it always needs replacing. A new motor costs $650, so that would be very disappointing. But the reality is, motors get replaced quite often within the warranty period after a diagnose by the dealer. It will not be taken apart and repaired. The broken motor will be sent to the manufacturer for them to collect data and improve their product. The standard warranty period on the motor is 2 years. This also goes for the replacement motor.

If an eMTB motor after the warranty period can be repaired or needs to be replaced, depends on the extend of the damage and the price of a replacement motor. It also depends on and the brand of the motor and to which extend replacement parts are available. Some manufacturers provide service kits.

As discussed, crank bearing are a very common part to fail. If that’s the only problem, they can almost always be replaced by a specialist. If other components have failed and if they can be replaced, is not certain and completely depends on the verdict of a mechanic. When it is cheaper to replace the complete motor, then that is the best option. Often is water and dirt is reason why parts fail. If this doesn’t get discovered in an early stage, it might not only ruin your bearings but also the circuit board and crankshaft. That might be the end for your motor.

If you notice any change in behavior and you act adequately, the chance of it being repairable, is bigger.

How To Recognize Motor Problems

There are a few things you can look for to find out if your motor is still healthy. If you focus on these signs, it will save you a lot of money in the long run. Contact the dealer for a consult.

Motor Noise

The noise of an ebike motor is not to everyone’s taste, but a change in sound is a good indication that something’s off. Creaking or grinding noises are not acceptable. If you’re unsure if it is the motor making the noise or the drive train, undo your chain and spin the crank.

Motor Behavior

Other than a change in motor noise, there might be a change in behavior over time. There’s a problem if the power delivery is intermittent or the motor keeps spinning after you stop pedaling. A bit of motor surge is normal.

Water Ingress

Look for any orange staining around your motor or the crankshaft. There might be a leak which lets water inside. If it’s relatively fresh, the damage might be limited.

Error Codes

There are a few sensor on an ebike motor like a torque sensor and a cadence sensor. If they detect something’s off, they will throw an error code. Always contact your dealer after an error code. Also when it disappears after turning it off and back on again. You never know when it reappears.

Crank Movement

To check if your crank bearings are still okay, you can grab both crank arms with your hands, and try to move them in- or outwards. They should be tight, but if there’s play, the bearings are worn.

Pedaling Resistance

Resistance in pedaling forwards or backwards is also a good sign of an unhealthy motor, even if there’s no noise. Most likely it is due to the bearings failing. When in doubt, remove the chain to exclude that the sound is coming from your drive train.

How To Make Your EMTB Motor Last Longer?

There are a few ways to prevent your motor from failing prematurely:

• Don’t ride in the highest mode of assistance all the time. Turbo might be cool, but the harsh acceleration and the amount of torque put through the system causes extensive wear.
• Don’t get your bike dirtier than needed. You don’t have to starting lifting it over puddles, but be a bit more gentle as you would on a regular mountain bike. It will save you time in cleaning and there’s less chance of dirt/water getting into the motor, so it’s a win-win.
• Clean your bike thoroughly after every muddy ride. Not only it prevents dirt buildup, it also gives you a chance to check for any abnormality, like orange staining or play in the crank.
• Do not derestrict or ‘tune’ your ebike. By derestricting you’re putting more stress on the system which will wear out its components faster.
• Never ignore an error code. Always get your bike checked afterwards even if the code disappears after switching the system off and back on again.

Frequently Asked Questions