WHEN should you stop pedalling to not DESTROY your motor ?

This may sound like an odd question, but it’s an important one as far as your motor is concerned. This article is written more for anyone who owns an ebike with an expired or expiring warranty.

We are probably all guilty of riding a bike with a worn wheel bearing or loose bottom bracket for instance. Many are familiar with the noise of a rough bearing. But, when it comes to an eBike motor, many seem to treat it no different to a normal, old fashioned, bottom bracket.

There is a slight difference of about £700 to £1200 between the two, so paying attention to what your motor's telling you could save you a small fortune.

Please note: We are not discussing terminal motor failure or breakage, we are only looking at the normal slow chronic failure that creeps in, often unnoticed. We will also look at the consequence of ignoring these noises.

Damaged Impulse 2 motor.jpg

An innocent Impulse 2.0 motor ridden to destruction

So how do you know when you should stop?

It will probably be a noise you hear before feeling anything. The problem is, if you start to hear this noise while riding, it’s normally already a bit late. If you start to feel a vibration, stiffness, or roughness through the pedals… It’s normally too late for a cheap fix.

Chronic (over time) motor failure usually start's with the bearings, we will look at that in-depth a little later. But, you can normally spot the symptoms very early…

Yamaha Bearing Race Damage.jpg

Another Yamaha ridden until the ball bearings broke through the bearing race and side cover!

How do I spot a problem in its early stages?

I'm often dumbfounded when people drop in to see us with their bikes and say… “I think I can hear a slight noise”. I drop the chain off the front chainring, spin the pedals and the crankshaft nearly drops on the floor !

Don’t get me wrong, I understand we’re not all mechanics; so below are some of the main things to look out for, how to check your motor and how to recognise potential issues.

First, familiarise yourself

This is best done when your bike or your motor is new or recently overhauled. First remove the chain from the front chainring to get rid of any chain or gear noise and turn the pedals by hand. Without the chain on, you will only be feeling and hearing the motor (and the pedal of course).

Once you are familiar with how your motor should sound and feel, you should be able to recognise any change. How often you should do this will depend on your riding terrain, weather, washing habits, how you transport the bike and so on.

Badly damaged Brose Motor.jpg

This Brose motor damage did not happen in one day!

What am I checking for ?

Once you’ve dropped the chain, start turning the crank arms. The first thing you will notice is that the motor makes a different noise depending on which way you turn the crankshaft, this normal. The motor is turning different components internally depending on crank direction.

What you’re listening for is a rough sounding noise like a hard plastic wheel rolling on a wooden floor, remember playing with a toy car on a wooden floor or desk ? It's a similar sound. On most motors this is easiest to hear when the crank is turned backwards because this usually allows the crankshaft to turn independently of the internal motor components .

Some motors, like the Bosch Gen 4, Impulse and Yamaha will click like a freewheel hub when turned in reverse, this is normal. Turning these particular motors in reverse only turns the left hand (non-drive side) bearing so best done from that side of the bike.

Some examples :

Brose motors (Specialized, Bulls, BH, Fantic etc.) when turned in reverse should be completely silent and very free and easy to turn.

Bosch Gen 2 and the Specialized Mahle motor should be smooth and quiet with a very slight amount of drag.

Bosch Gen 3 will be stiff to turn in reverse because the motor is not disengaged.

It is worth mentioning here that the Brose motor technically has 3 crankshaft bearings, this disguises premature bearing failure because the crankshaft tends to float on its centre bearing, usually this is the last one to fail. The crankshaft should be turned forcefully to try and side load it against the outer bearings.

Now, turn the motor forward. On all motors, this is best done from the drive side. With the exception of the Brose motor, all other motors should sound slightly louder. This noise should sound like two gears meshing, rather than someone racing a toy car over a hard surface - or worse, a coffee grinder!

The Brose motor should be almost as silent as it was in reverse, but there will be a very slight drag on the crankarm going forward .

You should feel no roughness through the pedal arm. Looking back at the second image (the Yamaha), this would have caused the crankshaft to bind and seize occasionally and would have felt very rough.

Depending on the motor make and model, you may feel movement in the crankshaft, either up and down (radial play) or in and out (end float), this should be minimal though. You can also try moving the chainring up and down to ensure the sprocket carrier or the spider it's fastened to are also relatively tight.

This is how your motor should feel :

Bosch Gen 1No play or end float on the crankshaft or sprocket carrier
Bosch Gen 2No play or end float on the crankshaft or sprocket carrier
Bosch Gen 3No play on the crankshaft but slight end float. Slight radial play on the sprocket carrier
Bosch Gen 4No play on the crankshaft but slight end float. Slight radial play on the sprocket carrier
Brose C, T, TF, S & S-MagNo play or end float on the crankshaft or sprocket carrier
Impulse 2.0, 2.3, EVO & EVO RSSlight end float on the crankshaft but no play or end float on the sprocket carrier
Mahle 1.1Slight end float on the crankshaft but no play or end float on the sprocket carrier
Shimano E7000, 8000 & EP8Slight end float on the crankshaft but no play or end float on the sprocket carrier
Yamaha PW, PW-ST, TE, CE, ST & Giant SyncDrive SportSlight end float on the crankshaft but no play or end float on the sprocket carrier
Yamaha PW-X, PW-X2 & Giant SyncDrive ProNo play or end float on the crankshaft or sprocket carrier
Note: End float differs from motor to motor but is generally around 1mm.

Why does this happen ?

Chronic ebike motor failure is usually a cascading event. Let’s look a very typical example :

A bearing will get a tiny bit of water in it, maybe from the ride, maybe when cleaned, maybe while on the car rack in the rain.

You put the bike away and for the next few days, weeks, months, the ball bearings start to rust to the bearing race. Next time you go out you may notice the crank sticks temporarily when you go to push the bike backwards, this usually signals the beginning of the end. The ball and race will have corroded together and once moved again both the ball and the bearing race will have a pitted surface, each ball going over that surface will now be damaged, and the wear will start.

Bearing issue deep dive

We are seeing hundreds of motors where if the failure was picked up a few miles earlier, the repair would cost £50 to £60. But , by the time the motor gets to us, it’s all but written off.

Perhaps I can explain in some detail what’s going on here. If you’re unfamiliar with some of the terminology, this may help as reference as we go a little deeper.

Below, is an example of a typical ebike motors crankshaft bearing. Its official name is "deep groove roller bearing", abbreviated to "bearing". This makes it difficult when talking about this topic because the ball bearings inside the bearing are also called bearings. For the purpose of this article, I will call them “ball bearings” going forward.

Deep Groove Roller Bearing.jpg

Deep Groove Roller Bearing - Terminology

It's rarely understood how fast a bearing can deteriorate and what happens once it starts. Firstly, most crankshaft or drive bearings in the latest ebike motors are designed for weight saving, so these tend to be relatively large bearings containing very small ball bearings within them.

This means when water, dust or grit penetrates the bearing the wear rate is extremely fast. Unlike a bearing with large ball bearings, these will generally last quite a few rides before destruction. Not that this helps some people!


Badly worn bearings.jpg

Large ball bearings worn so badly they are dropping out the side of the bearing.

What happens?

As the inner ball bearings wear, they become smaller and begin to allow movement or “radial play” in the bearing, this allows the inner bearing race to move with the piece its attached to. This movement of the inner bearing race starts to wear the bearing seal and slowly begins to lift the seal away from the race it’s sealing against.


Lifted inner bearing race.jpg

The inner bearing race has lifted from the bearing seal and lack of lubricant has damaged it.

Once this situation begins, it allows even more dirt, grit and water into the bearing - speeding up the wear until there is enough room for this contamination to pour into the motor itself.

This “small ball bearing” type can go from slightly noisy to completely destroyed in one ride.

Damaged bearings.jpg

Daylight should not get through your bearings

What happens if you ignore the noise ?

You really do this at your peril and at the risk of killing your motor. All ebike motors are assembled in cleanroom conditions which are generally pristine inside. There is no oil or filters, so nothing to catch any contaminants.

Anything which gets into the motor is in there for life. (Always makes me cringe watching YouTube when a motor is being assembled on a grit strewn bench or dirty towel).

Once contamination begins, it starts a chain reaction. The particles coming from the failed component starts spreading to the other components and then it’s all downhill .

Once dirt or water ingress into the motor, it’s just a matter of time before you’re walking home.

Why are these bearings so bad, why do they let the water in in the first place ?

Don’t be so hard on the bearings, it’s not really their fault. Bearings are not designed to be waterproof; it would lead to far too much friction if they were.

There are many different types of bearing seals available from open metal shields to the best rubber “labyrinth” type seals, but even these are just slash proof, fine in the rain or road puddles, but not so good against a deep water crossing, a long flooded rut, garden hose, car rack in the rain and so on.

Why don’t the motor manufacturers fit a seal in front of the bearings ?

Seals add friction and friction = less battery range . It's as simple as that.

90% of the ebike market is made up of commuter and road bikes, especially in Europe. These bearings are fine in the rain so why add extra friction.

How do you sell your motor if it doesn't go quite as far as your competitor on a full charge?

Shimano and Mahle are sealed but they still have bearing problems

This is true but the seals they use are springless - to keep friction down, relatively small, and in the case of Shimano very soft. They are still no match for a keen garden hoser or a pressure washer and they will both still allow grit to creep in.

Damaged Bosch Gen1.jpg
A Bosch Gen 1 ridden while full of mud until the dirt build-up shattered the gear.
Bosch Gen2 Disintegrated Bearings.jpg
A Bosch Gen 2 ridden until the bearing disintegrated and the ball bearings wore through the motor casing
Gen4 Bosch seized crankshaft.jpg
A Bosch Gen 4 ridden with a seizing crankshaft until the ratchet at the bottom could no longer grip.


Stripped Brose Belt.jpg
A Brose ridden for miles after the belt stripped and snapped, filling the motor with carbon dust
Brose Full of Mud.jpg
A Brose ridden while full of mud.


Bosche Gen2 steel dust.JPG

A Bosch Gen 2 thoroughly contaminated with steel dust
Gen 4 Destruction 2.JPG
Gen 4 Destruction 3.JPG

The source of all the steel dust
Gen 4 Destruction 4.JPG


Yamaha Motor Bearings Failure.jpg

A Yamaha ridden until the ball bearings broke through the motor cover leaving just the inner bearing race and a bit of seal.

I probably have 3,000 or 4,000 more photographs just like these 😥

Next time you’re thinking… "It feels a bit rough, but it should be fine! I’ll just go for one more ride before I get that noise sorted out"

GAME OVER !

But you own a motor repair business, why are you telling me this!?


To be honest, this is a win, win situation . If we can repair your motor, you save money, and we make money. If you damage your motor beyond economical repair, it costs you 3 times as much and we make nothing!
About author
Bearing Man
I own and run the Ebike Motor Centre where we sell spare parts and bearings for ebike motors. We also offer a full repair service for most ebike motors.

Comments

Fantastic write up. These are some pretty gruesome failures. Interesting to see a map of where the correlation is to mud riding. Lot of these pics show extensive water intrusion. I live in southern California and never wash the bike. So far so good.
 
Brilliant, thank you. This gent is so helpful - I literally called him late this afternoon because i have play developing on my PW-X2. Initially I was thinking its just my OCD kicking in, but after a quick chat I know its time get a warranty claim going before it runs out in a couple of months. Thanks again fella!
 
When the belt on my Spesh started stripping I got off and pushed it a long way back to the trail head - only coasting down hill.
Even though I knew it was a warranty issue, right from the time I started riding MX bikes I gained a fine appreciation as to when I should shut the sucker down. Too often at my LBS I see bikes come in that were ridden well past when an issue first occurred with the excuse - "Well, it happened on Saturday, but since we were at the bike park all weekend I kept on riding." I have no patience for that.
 
What an exceptionally well written and illustrated article. I enjoyed that, and it’s maybe pushed me to pull mine and get it bloody serviced by you guys! I’ve been neglectful since we solved the shutdown problems and the bike has been riding just fine for all most 9 months!
 
Great article and very interesting write up. My question is:

If my motor is making a nasty noise, should I just ride it until it stops, because it's probably scrap anyway?
 
Great article and very interesting write up. My question is:

If my motor is making a nasty noise, should I just ride it until it stops, because it's probably scrap anyway?
You would be surprised at whats fixable! Just bear in mind that every turn of the pedal is costing you more money :unsure:
 
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Great write up. Its good to see it all in one place. After reading your comments over the past couple years I've started to be very careful with water ingress and after nearly 2 years I've not had a single problem with my motor.
If I'm not mistaken, you don't service Shimano motors anymore correct?
The bearings are also not available to purchase and custom made? (EP8)

Heres hoping to being careful giving the motor another 2 years.
 
Is there a diy stuff that we can do to prevent such a failure? Like changing the bearings ourselves? Or does it void the warranty or needs specialist equipment and experience? I usually do all servicing myself, but the motor I didn't touch yet.
 
Great write up. Its good to see it all in one place. After reading your comments over the past couple years I've started to be very careful with water ingress and after nearly 2 years I've not had a single problem with my motor.
If I'm not mistaken, you don't service Shimano motors anymore correct?
The bearings are also not available to purchase and custom made? (EP8)
Thank you, We have just made an EP8 bearing kit and this will be available within the next 2 or 3 weeks. We are also considering offering a repair service for this particular motor too.
 
Is there a diy stuff that we can do to prevent such a failure? Like changing the bearings ourselves? Or does it void the warranty or needs specialist equipment and experience? I usually do all servicing myself, but the motor I didn't touch yet.
Preventative DIY is only really possible with the Bosch Gen 4. All other motors are more or less fit and forget.

If your motor is still in warranty, don't touch it. Other than that, we tend to advocate people fixing their own things, we sell all the bits and offer help if needed. However, the "have a go" attitude should take a few things into account first e.g. Level of experience, workshop equipment mechanical knowledge etc.
It's worth bearing in mind that we do get an awful lot of motors where someone has "had a go"! It just means a lot more work for us, cleaning out the wrong grease, bits of grit and dirt, removing snapped screws, dressing out all the screwdriver marks in the gasket faces, turning the bearings the right way round etc. Also remember, not all parts are available for all motors, so mind what you break!
 
I have the bosch 4th gen, how would you prevent water ingress? I guess putting a 1 cm layer of grease all around is not very smart :D
 
I have the bosch 4th gen, how would you prevent water ingress? I guess putting a 1 cm layer of grease all around is not very smart :D
This is a good question actually. The Bosch Gen 4 has a cover that sits over both left and right crankshaft bearings. These are half way between a seal and a shield. The idea is that they are removed after un undisclosed period of time, cleaned and re-greased or replaced (they do wear out). If left ungreased, they can add a lot of drag to the motor too.
Bosch don't specify a time or a mileage at which point this work should be done and this is probably because it will depend on your riding terrain, weather conditions, washing habits etc. If you live in the UK I would say take a look after 2 months, if there is still clean grease behind the "seal" leave it 3 months next time etc.
There is a kit for this, that contains new seals, circlips and the Bosch long life "tacky" grease.
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Scary! I'm beginning to have second thoughts about looking for a second hand emtb, especially as I haven't had one before so don't know what to expect...
 
Congratulations for the article, it is really good.
I have two EBike with DU-E8000, one with 30,000 km and another with 17,200 km, neither has given me engine problems so far and I never changed bearings.
How many kilometers can a DU-E8000 do?
 

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Congratulations for the article, it is really good.
I have two EBike with DU-E8000, one with 30,000 km and another with 17,200 km, neither has given me engine problems so far and I never changed bearings.
How many kilometers can a DU-E8000 do?
My E7000 is just approaching 10,000kms. However, I believe I'm right in saying that the E7000 can't be serviced/repaired anyway, is that right @Bearing Man?
 
Scary! I'm beginning to have second thoughts about looking for a second hand emtb, especially as I haven't had one before so don't know what to expect...
Don't let this put you off Stuart, you will be fine if you just keep an ear out for anything untoward and get it looked at sooner rather than later. Many people do thousands of happy trouble free miles. Don't forget we also see these motors in near perfect condition after 60,000 + miles! (100,000 Km's).
 
Congratulations for the article, it is really good.
I have two EBike with DU-E8000, one with 30,000 km and another with 17,200 km, neither has given me engine problems so far and I never changed bearings.
How many kilometers can a DU-E8000 do?
Motor mileage is un-quantifiable due to the amount of variables e.g. Riding terrain, weather conditions, washing habits, how you transport your bike etc. There are still E8000 motors out there running like yours, so we don't yet know what their ultimate mileage in the optimum conditions would be?
My E7000 is just approaching 10,000kms. However, I believe I'm right in saying that the E7000 can't be serviced/repaired anyway, is that right @Bearing Man?
The E7000 can be a little difficult because the PCB is not removable without de-soldering it and it sits in the way of some of the components, but it is doable if you have the skills and patience.
Please note, we no longer currently repair Shimano motors.
 
Motor mileage is un-quantifiable due to the amount of variables e.g. Riding terrain, weather conditions, washing habits, how you transport your bike etc. There are still E8000 motors out there running like yours, so we don't yet know what their ultimate mileage in the optimum conditions would be?

The E7000 can be a little difficult because the PCB is not removable without de-soldering it and it sits in the way of some of the components, but it is doable if you have the skills and patience.
Please note, we no longer currently repair Shimano motors.
I only hope it will last half as long as my 90 Orbea Karakorum.
Best regards.
 

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Hi Pete,
Thanks for your time on the phone the other day and the speedy service too.
I was going to ask you, but had already taken up too much of your time, is there anything worth looking at to try and keep the water at bay, aside from dont wash the damn thing? My typical useage is this kind of trail up at Glentress and water cannot be avoided for the next 6 months at least.

Still from last weeks Glrentress video entering Thunderstruck...
You probably had to empty some of that fine Scottish forest out of my motor... LOL

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I have considered regularly covering the outer face of the mainshaft/bearing interface both sides with a marine grease but then I start to think its probably just pointless. But.. is it?
 

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