Bosch ebike motor reliability

Tofu21

Finding my (electric) wheels
Aug 9, 2017
16
1
48
U.K.
I have got a hardtail Bosch performance line CX ebike and I’ve had it for about 3 months.

The bearings in the original motor died after a month. I had that replaced under warranty which was great.

I think the replacement motor has just failed in a similar way.

If I need a new motor ever 4-6 weeks it’s going the get boring real soon....

I went on one of those proper wet rides last weekend so wonder if that has anything to do with it or if the motor is taking a lot more battering than if it was in a full sus frame with it being a hardtail.

Has anyone else had similar problems?
 
D

Deleted member 4366

Guest
Is this the next big story? Lots of rumours and reports floating around of Bosch CX bearings failing. Hopefully, it's fixed in the 2018 models, which use a different version of the motor, but previos versions will me much harder to sell in the used market, like Kalkhoff Impulse 2 bikes.
 
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Trevormonty

Esteemed Pedelecer
Jul 18, 2016
1,135
564
17
NZ
The active drive been replaced with new Active Cruise and Active Plus, both quieter and running large direct drive chainring.
Performance and CX unchanged at present on outside at least. I'd expect both to be replaced with more compact quieter version using larger direct chainring in 2019, hopefully it get better user interface. To compete with likes of Shimano E8000, Bosch can't afford not to upgrade CX drive. Discounting of CX is only way they can keep market share until new drive is released, by then E8000 will be well established and hopefully with good reliability record.

If you doubt me regarding discounting, look range Cube ebikes running CX drive, they are not limited to eMTBs.
 

Gringo

Esteemed Pedelecer
Jun 18, 2013
1,333
835
Northampton
If that is the case, I’m stuck with a £3k chocolate fire guard
Bosch can't aford not to do somthing about this problem, once lost a good reputation for quality will take many years to recover, especialy now as the ebike market is expanding rapidly. Like d8veh said above about Kalkhoff, people don't think of a spesfic modle they just know Kalkhoffs are unreliable.
All that said, if I owned a CX bike and it failed like yours I'd be demanding a full refund as its "not fit for purpose". For 3K I'd take it to the small claims court
 

bigclick

Pedelecer
Sep 11, 2014
206
52
63
So I am about to handover my hard earned for a Moustache Race 9 and now I'm thinking the CX is already old technology

Making me think twice now, can someone, anyone please argue the case for CX now against waiting for CX 2.0?
 

Tofu21

Finding my (electric) wheels
Aug 9, 2017
16
1
48
U.K.
The bike shop is talking to Bosch and the bike rep tomorrow and will see what they come up with.

I have heard rumours they are rengineering the CX motor to make it more reliable. I can half see me killing old motors until they come out with the new one.
 

Tofu21

Finding my (electric) wheels
Aug 9, 2017
16
1
48
U.K.
So I am about to handover my hard earned for a Moustache Race 9 and now I'm thinking the CX is already old technology

Making me think twice now, can someone, anyone please argue the case for CX now against waiting for CX 2.0?
Based on my experiences with my bike I can’t currently recommend the Bosch CX motor.
 

bigclick

Pedelecer
Sep 11, 2014
206
52
63
Based on my experiences with my bike I can’t currently recommend the Bosch CX motor.
Sounds like you have had a bad motor so your opinion is justifiably polarised. My conundrum is around the Bosch road map and if depriving myself of a new bike is worth the wait for a direct drive CX. I mean is there definitely one on the cards for next year?
 

Tofu21

Finding my (electric) wheels
Aug 9, 2017
16
1
48
U.K.
The Bosch system is great when it works it’s great.

I’ve had two motors and both have died in a mater of weeks. So yep I’m very sceptical of the Bosch reliability.

I do wonder if being in a hardtail is giving the motor more of a hard time than a full sus. Not that I’m a massively aggressive rider so I’m just guessing...
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
19,991
8,173
60
West Sx RH
There is a possibility like the impulse 11 that these units are being asked to deliver to much power/torque with the wrong gearing selected by riders, the drives just can't handle it with under engineered components failing to quickly.

Over the years Eddie has really given his bosch drives a good pasting/workout, so is in a good place to extol there reliability/longevity though would be interested in how many drive issues he has actually suffered. Eddie though is hot on maintenance and gearing so doubt that he strains/stresses the drive which may lead to early failure.
 

EddiePJ

Esteemed Pedelecer
Jul 7, 2013
4,632
4,011
Crowborough, East Sussex
www.facebook.com
Hi Neal, I was wondering when my name would eventually crop up in respect of the increasing amount of Bosch related motor failure threads. Not just on this site, but elsewhere on other ebike related forums and FB groups.

Bear with me on this, as it a long and rambling one.

I don't believe that any make of current crank drive electric motor (DU) as fitted to eMTB's is not going to be susceptible to outer bearing failure, especially if the bike is used in Europen off road conditions. You only have to look at how often bottom bearings fail on non electric bikes to format a reasoning that the same would be true of an electric motor that is in effect replacing that bottom bracket.
It is my opinion that until a manufacturer designs what could be called a pre unit motor, that some how separates the motor from that bottom bracket, that this will never change. The bottom bracket would still fail, but it will be a separate, mechanical component, rather than an electrical one.

Now to the point in question in respect of Bosch DU's.

Yes I have had drive unit failure, and below are my thoughts in respect of the system.


Firstly, if the motor makes it to 600 miles, then you are more than likely going to be okay. It seems to me that many motor failures happen within this initial mileage. The next stage is 600 miles to 2,300, and then 2,300 miles plus. I personally feel that sooner or later, that any/all of the current DU's which are used in an eMTB, will eventually fail.

This leads to the reason of why. Do you all recall the Bosch popping sound of the previous incarnations of Bosch motors. The reason for this was lack of grease within, and it was an issue easily solved. An issue that should never have even happened, and also one that Bosch denied liability of, for a significant period of time.

The current DU's don't suffer from that problem, but do suffer from outer bearing failure. Unless someone can tell me otherwise, I am only aware of the failure occurring on the sprocket side.
I'm not an engineer, but through years of working on motorcycle race bikes, I do have a thorough mechanical understanding, and it is my belief that the current use of the small size sprocket, is placing undue strain and load on the drive side, which is then creating fractional wear. This fractional wear, is then allowing undue moisture to enter the bearing area, and accelerating bearing failure rate. This doesn't explain the early mileage failure rates though. I have also noted that failure rates occur more on the bikes of fitter riders, where by lower power settings are used, and more strain is being transferred through the pedal cranks. I suspect that riders that aren't so fit, or riders that use higher power settings might not suffer so many DU failures. Again this doesn't explain the low mileage failure rates. Perhaps a conspiracy theory, but I also feel that eMTB mode was introduced to try to prevent these failures, by offering an assistance over and above the requirement of the rider, and so reducing strain. Despite claims, the system is not intuitive.

Another reason for DU failure, is poor cleaning teqnique method of the bike and it's DU. The fastest way to destroy the outer bearing (again the drive side) is the use of high pressure hosing down, and or the use of cleaning detergents and oils. I frequently cringe at the teqnique used by many to clean their DU's. I also cringe when I see dealers recommending using detergents, degreasers, and oils around any bearing area whatsoever. Don't do it!

The above leads nicely on to the laughable cure of the bearing failure issue. The Bosch outer bearing seal modification. I'm not going to hold back on this, as I think that it is a complete cop out, and a poor one at that.
The idea being that grease is first put behind this seal, and a plastic ring then pushed over to prevent water ingress. This will only work, if the owners removes this seal at least once a month, and re greases it. Even then, it is a touch and go situation.
Taking this one stage further, the seal is now fitted as standard, and I removed the seal on my current bike, after just a few weeks of use, and discovered that from the factory, no grease had even been applied (Back to my above statement about the Bosch popping sound and the lack of factory supplied grease) Are the sealed bearings even of suitable quality, do they have a suitable grease, and if the first prevention stage is being completely missed out, who knows! I now remove and re grease the seal very two or three weeks. Should I need to, and should I have needed to add the grease that the factory choose to leave out, no I shouldn't.


Also in respect of my current motor, the motor refused to turn on from new, and just kept shutting down. I claim to know very little of how an electric bike functions, but it doesn't take much to work out that there is either a software issue, battery issue, or power issue. Trying parts on my other bike, everything apart from the motor was quickly eliminated. Two things were left. Either the motor was duff, or there was break in the connection between the battery and the motor. I tried everything that could think of, but nothing. Then out of desperation, I shone a torch into the plug of the motor, and there was the issue. One of the pins had been bent flat during the assembly stage. I very carefully straightened the pin, and everything worked first time. The pin will now be permanently weakened, so who knows when that will fail, and the motor will die. Probably the first time that the plug is removed. I do wonder if that doesn't also explain the odd thread that you read of, where an owner receives a new bike, only to have it not turn on.

I'm fed up of people saying that I am biased towards Bosch. I do love the system, and I'm more than happy with both the performance, and the support that as a company that they give to all, and see no reason for me to switch away from the brand. To date, no other brand even appeals to me.
I'm not prepared to pretend that the design isn't flawed though, and until the company revert back to a conventional size sprocket, or carries out a proper re design of the current system, then I predict that these failures shall continue.
One other aspect to think about, is that no one has any idea of the quantity of DU's produced daily, so the actual the percentage failure rate could in relative terms, be close to zero. Obviously that is of no consolation to those that do suffer a failure though, and I'm certainly making no defence of it. To end, even with a motor re design, only a pre unit motor will prevent bearing failure.

My gripe isn't oddly with the motor, my gripe is with the batteries. The mileage that they give after just a year of use, declines quite significantly, or that has at least been my repeated experience. I also don't like the fact that as a company, they do not listen to customer concerns in respect of either design, or factory installed software. I have discussed this with Bosch de.
 
Last edited:

Paul smith

Pedelecer
Mar 26, 2016
249
198
This thread quite worrying..punters paying 2-£3000-£4000 grand for a bike that claps out after a few hundred miles..wouldn,t buy a washing machine from bosch never mind a 3 grand bike...their hoovers quite handy though ..so I heard..
 

Tofu21

Finding my (electric) wheels
Aug 9, 2017
16
1
48
U.K.
Hi Neal, I was wondering when my name would eventually crop up in respect of the increasing amount of Bosch related motor failure threads. Not just on this site, but elsewhere on other ebike related forums and FB groups.

Bear with me on this, as it a long and rambling one.

Firstly, I don't believe that any make of current crank drive electric motor (DU) as fitted to eMTB's is not going to be susceptible to outer bearing failure, especially if the bike is used in Europen off road conditions. You only have to look at how often bottom bearings fail on non electric bikes to format a reasoning that the same would be true of an electric motor that is in effect replacing that bottom bracket.
It is my opinion that until a manufacturer designs what could be called a pre unit motor, that some how separates the motor from that bottom bracket, that this will never change. The bottom bracket would still fail, but it will be a separate, mechanical component, rather than an electrical one.

Now to the point in question in respect of Bosch DU's.

I had a series of failures in the early stages, and quickly came to several conclusions.

Firstly, that if the motor makes it to 600 miles, then you are more than likely going to be okay. It seems to me that many motor failures happen within this initial mileage. The next stage is 600 miles to 2,300, and then 2,300 miles plus. I personally feel that sooner or later, that any/all of the current DU's which are used in an eMTB, will eventually fail.

This leads to the reason of why. Do you all recall the Bosch popping sound of the previous incarnations of Bosch motors. The reason for this was lack of grease within, and it was an issue easily solved. An issue that should never have even happened.

The current DU's don't suffer from that problem, but do suffer from outer bearing failure. Unless someone can tell me otherwise, I am only aware of the failure occurring on the sprocket side.
I'm not an engineer, but through years of working on motorcycle race bikes, I do have a thorough mechanical understanding, and it is my belief that the current use of the small size sprocket, is placing undue strain and load on the drive side, which is then creating fractional wear. This fractional wear, is then allowing undue moisture to enter the bearing area, and accelerating bearing failure rate. This doesn't explain the early mileage failure rates though. I have also noted that failure rates occur more on the bikes of fitter riders, where by lower power settings are used, and more strain is being transferred through the pedal cranks. I suspect that riders that aren't so fit, or riders that use higher power settings might not suffer so many DU failures. Again this doesn't explain the low mileage failure rates. Perhaps a conspiracy theory, but I also feel that eMTB mode was introduced to try to prevent these failures, by offering an assistance over and above the requirement of the rider, and so reducing strain. Despite claims, the system is not intuitive.

Another reason for DU failure, is the due the owners cleaning method of the bike. The fastest way to destroy the outer bearing (again the drive side) is the use of high pressure hosing down, and or the use of cleaning detergents and oils. I frequently cringe at the teqnique used by many to clean their DU's.

That leads to the laughable cure of the issue. The Bosch outer bearing seal modification. I'm not going to hold back on this, as I think that it is a complete cop out, and a poor one at that.
The idea being that grease is first put behind this seal, and a plastic ring then pushed over to prevent water ingress. This will only work, if the owners removes this seal at least once a month, and re greases it. Even then, it is a touch and go situation.
Taking this one stage further, the seal is now fitted as standard, and I removed the seal on my current bike, after just a few weeks of use, and discovered that from the factory, no grease had even been applied (Back to my above statement about the Bosch popping sound and the lack of factory supplied grease) Are the sealed bearings even of suitable quality, do they have a suitable grease, and if the first prevention stage is being completely missed out, who knows! I now remove and re grease the seal very two or three weeks. Should I need to, and should I have needed to add the grease that the factory choose to leave out, no I shouldn't.


Also in respect of my current motor, the motor refused to turn on from new, and just kept shutting down. I claim to know very little of how an electric bike functions, but it doesn't take much to work out that there is either a software issue, battery issue, or power issue. Trying parts on my other bike, everything apart from the motor was quickly eliminated. Two things were left. Either the motor was duff, or there was break in the connection between the battery and the motor. I tried everything that could think of, but nothing. Then out of desperation, I shone a torch into the plug of the motor, and there was the issue. One of the pins had been bent flat during the assembly stage. I very carefully straightened the pin, and everything worked first time. The pin will now be permanently weakened, so who knows when that will fail, and the motor will die. Probably the first time that the plug is removed. I do wonder if that doesn't also explain the odd thread that you read of, where an owner receives a new bike, only to have it not turn on.

I'm fed up of people saying that I am biased towards Bosch. I do love the systems, and I'm more happy with both the performance, and the support that as a company that they give to all, and see no reason for me to switch away from the brand. But I'm not prepared to pretend that the design isn't flawed, and until the company revert back to a conventional size sprocket, I see these failures continuing, and even then, as I said in the beginning, only a pre unit motor will prevent motor failure.

My gripe isn't oddly with the motor, my gripe is with the batteries. The mileage that they give after just a year of use, declines quite significantly, or that has been my experience. I also don't like the fact that as a company, they do not listen to customer concerns in respect of either design, or factory installed software.
Interesting thoughts, which make a lot of sense.

I’ve killed a few BBs in my time but never in 7 rides

I’m bracing myself for a pain in the ass with this bike.
 

Ducknald Don

Pedelecer
Sep 2, 2017
97
38
Oxfordshire
It will be interesting to see how mine pans out, I've been doing 100 miles a week and expect to continue at that rate. Ten weeks and so far no problems (apart from falling off).
 

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