A major motor failure on an e-MTB is pretty much the worst-case scenario for any e-biker. Firstly, the tour is over and secondly, it can be very expensive. But this nightmare becomes reality more often than you might think: leaks in the bottom bracket shaft have led to water and dirt ingress in various motors belonging to our readers, as well as colleagues in the editorial team - and thus to damage inside the motor. The Performance Line CX from market leader Bosch was also affected. The motors were replaced as a gesture of goodwill by the specialist dealer. However, touring ambitions had to be put on hold for the time being.
Water cannot be avoided on an E-MTB. After all, a bike that is ridden intensively needs to be washed regularly. And even on a tour, an unwanted full bath can happen during a crossing. If the crank or the entire motor is submerged for a short time, the thick grease pack should seal the system, but this is not guaranteed. Under no circumstances should you open the housing yourself after the immersion bath, but instead visit your specialist dealer as quickly as possible. In any case, it is advisable to always carry an absorbent microfibre cloth with you in your rucksack when you are on the move - this will help you to dry out the precarious areas as quickly as possible.
The motors of all manufacturers are sealed against water, and this is often certified according to international standards. There are differences in the degree of waterproofing and - above all - how openly the manufacturers deal with information about it. With reference to trade secrets, Shimano could only be elicited that there had been no proven water damage to Shimano motors to date. When asked, Bosch explained: "Our engineers have optimised the composition and quantity of the grease pack acting as a sealant and introduced an additional bearing protection ring. These technical improvements are also available to users of older CX-Drive units as retrofit kits from specialist dealers."
WASH
Remove the battery and display. Their contacts are sealed against water. Wet the dirty bike with water, spray on bike cleaner and leave it to work for a few minutes. Rinse off the softened dirt with hose water or wipe it off the bike with a sponge. Make sure that the water pressure is not too strong when rinsing and it is better to spray from an oblique angle. Then rinse thoroughly and dry well. Do not allow moisture to build up anywhere. The weak point of bike motors is where the bottom bracket shaft penetrates. Therefore, never point the garden hose directly at the shaft bearing.
TRANSPORT
It is best to transport your e-MTB protected in the car. If you use an external rear carrier, you should always remove the display and battery - especially in summer weather to protect the battery from excessive heat. In rainy weather, a securely lashed protective cover helps to prevent dirt and moisture from getting on the bike. But even unpacked, you need not fear a rain shower on the motorway: The seals on the electrics and engine can cope with wet conditions even in the full force of the wind.
DOS & DONT'S
- Remove an external battery for washing. This also allows you to clean the gaps, the water drains away completely and you can dry well afterwards.
- With integrated batteries, make sure that no moisture collects under the cover.
- Always dry the bike after washing. An absorbent microfibre cloth can also be used to carefully dry angled contact points.
- High-pressure cleaners are taboo! The hard jet of water undermines seals and flushes grease out of the bearings. To be on the safe side, never point the jet of a garden hose directly at the bottom bracket shaft, contacts or plug connections.
- Before installing the battery and display, apply a small amount of contact spray to all electrical contacts to displace any remaining moisture and prevent corrosion.
- Remove the battery and, if possible, the display and control unit for transport on the car carrier: This reduces the load on the carrier, prevents theft and damage caused by jostling and protects against excessive sunlight.
- Battery and display contacts do not need to be covered even in the rain. Before installation, however, clean with a microfibre cloth, dry and occasionally treat with contact spray.
- If you pack your bike in a cover on the outer rack, you should unpack it immediately on arrival to avoid a damp microclimate.
- Stow the battery safely and securely in the car. It must not fly around in the car, even in the event of emergency braking or an accident.
TIPS
It is best to clean the bike thoroughly after every ride. However, always keep at least the area of the crankshaft around the crank and chainring clean. This will prevent dirt from accumulating, which can be washed into the crankshaft bearings when wet.
If moisture has already penetrated the motor, do not open the housing yourself under any circumstances. Contact
the specialist dealer as soon as possible.
If you hear any unusual noises from the motor, contact your specialist dealer immediately. Most manufacturers recommend having the E-MTB checked regularly once a year by a specialist dealer. The motor seal will also be checked during the service and replaced if necessary.
Bosch has responded favourably to reported cases of damage and, according to its own information, is also making a retrofit kit with improved seals and modified grease available for older engines via specialist dealers.
WATER PROTECTION ACCORDING TO STANDARD
The degree to which an electrical unit - for example an e-MTB motor - is protected against the ingress of dirt and water, but also against the fingers or tools of curious users, is categorised worldwide with so-called protection classes according to the IP standard. The first of the two-digit IP number sequence indicates the level of protection against foreign bodies and contact, the second digit against water. However, this classification is very general, as it is also used worldwide for domestic power installations, industrial plants or outdoor mobile phones. In practice, this means that even the highest protection class 6, which only Brose offers, cannot protect a motor in the event of short-term submersion in a stream or direct bombardment with a high-pressure cleaner. What is meant by the keywords spray, splash or jet water in the definition of the standard is also not absolutely certain. Our research with the motor manufacturers Bosch, Brose, Shimano, Yamaha and Rocky Mountain revealed quite different opinions. They all agreed that rain showers on the road or washing with a garden hose are not a problem for any MTB motor. However, no manufacturer has planned for brief submersion when crossing a stream. Only a specialist dealer can determine whether water has really got in. So it's better to get it serviced immediately!
THE IP STAGE
The degree of protection IP (International Protection Code) indicates the suitability of electrical units for operation under various environmental conditions. The second digit is relevant for water tightness. Our survey of the most important motor manufacturers revealed different classifications for the drives: Bosch and Yamaha drives have IP54, which means that "splash water on all sides" is kept away from the inside of the motor. Brose classifies its drive with IP56 - the number 6 means that the motor resists "strong water jets". Rocky Mountain, like Shimano, does not assign a protection class at all. The Rocky motor is structurally separated from the bottom bracket, which makes it much less sensitive to water. Shimano only tests according to its own procedure, without saying how.
The IP ranges relevant for e-bike drives protect against the following in detail:
IPX4: splash water on all sides
IPX5: Water jets from all angles
IPX6: Strong water jets
Level 7 or 8 would be required against temporary or permanent immersion, and even protection class 9 against high-pressure cleaners.
Interview with Dipl.-Ing. Dirk Zedler, bicycle and e-bike expert
In your experience as an expert, is water damage to e-bike motors becoming more frequent?
I am not familiar with this particular problem. However, when I hear that the question relates specifically to e-MTB motors, I immediately think of the use of high-pressure cleaners. These are also good for bikes, but even less so for e-bikes. With water pressure of over 100 bar in some cases, all grease is washed out and every seal is rinsed out. That's why I have always advised against high-pressure cleaning on bikes in general.
So are current e-MTB drives sufficiently protected from the wet?
When it comes to information on operational safety, which also includes protection against moisture, drive manufacturers generally tend to keep a low profile in order to be on the safe side in the event of damage. The conservative specification of IPX4, protection against splash water, may well mean that the drive can withstand brief immersion in a stream. However, consumers should not rely on this. You should therefore not base your purchase decision on the waterproof rating of a system.
Is a generally formulated protection class such as the IP standard at all suitable for dealing with the complex, specialised topic of
E-MTB to grasp?
That is the general problem with standards. How can you define a water jet from a garden hose if you don't have a constant fluid under laboratory conditions? That's why well-researched, practical instructions on cleaning and care in the trade press are so important.
