WARNING! To Bosch powered ebike owners (pre 2020)

[Bearing Man]

I have posted this on the general forum in the hope of reaching as many Bosch powered bike owners as possible.
About a year to 18 months ago, Bosch started supplying and fitting a felt seal. It fitted behind the circlip on the right hand side of the crankshaft, in the space between the crankshaft and the sprocket carrier. The idea was to protect the right hand crankshaft bearing from dirt and water ingress. This would be fine, if this part was well maintained and fitted to a road bike. Off road is a completely different story.

We are seeing some big issues on motors fitted with this felt seal. The felt is acting as a sponge and retaining water against the very bearing it was designed to protect. In the case below it has allowed enough water past to destroy the large clutch bearing and freewheel bearing surface too. It is also badly rusting the crankshaft, making the motor very difficult to get apart. If the felt is oiled or greased, it catches the grit and dirt and becomes a scouring pad, wearing into the crankshaft or soft aluminium sprocket carrier.

In the first set of images, you can see that this was not an old motor, the plastic gears are in excellent condition but the motor was almost destroyed.
In the second set of images, you can see a soaked felt that we pulled out after 1 month and it has already become sand paper!

If you own a Bosch powered mountain bike manufactured between 2015 and 2019 it will be fitted with this Gen 2 motor (no it's not a Gen 3, they were only fitted to road bikes and a few gravel bikes. Small chainring Gen 2). And if you have had a Bosch service kit or a new motor fitted within the last year to 18 months, check that this seal has not been fitted.

If you have had any work done by us at Performance Line Bearings, we have always refused to fit this part, preferring to fit our double lip rubber seal. But sadly it was in the BDU2xx service kits that we sold and may have been used by others.

There was a very good reason why the automotive industry stopped using felt seals back in the 50's!

 

[IndigoUnicorn]

Can a better seal be order and fitted at my LBS? I’m in the US, so a supplier and part number would be extremely useful.

Thanks for the heads up!

 

[Bearing Man]

Can a better deal be order and fitted at my LBS? I’m in the US, so a supplier and part number would be extremely useful.

Thanks for the heads up!

Yes, just have a chat with our US partner, he has stock of both the MudStop and crankshaft seal.

 

[Beekeeper]

I’ve been using the felt seal and just replaced the old one which was in for a year with a new one. I always put green tacky grease behind it and around the sides before putting a new circlip back on.

Fortunately the old felt ringlooked in pretty good shape as I don’t really ride in wet or muddy conditions.

the tacky grease was all still there and there was only a small amount of dust on the front side of the felt.

I agree, your rubber seal looks the better long term option. Do you advise applying tacky grease when inserting the rubber seal?

 

[Bearing Man]

I’ve been using the felt seal and just replaced the old one which was in for a year with a new one. I always put green tacky grease behind it and around the sides before putting a new circlip back on.

Fortunately the old felt ringlooked in pretty good shape as I don’t really ride in wet or muddy conditions.

the tacky grease was all still there and there was only a small amount of dust on the front side of the felt.

I agree, your rubber seal looks the better long term option. Do you advise applying tacky grease when inserting the rubber seal?

exactly, keep it well greased (maintained) and dry, no problem. But un-greased, wet or dirty and that’s when the problems start.

When I fit a rubber seal, I pack the back of the seal with tacky grease and also the bridge between the two lips of the seal.

 

[maker]

I got my third motor and have 10 months warranty left. This motor is lasting much better than previous two. Whilst it sounds OK there may be damage so don't want to replace seal in case Bosch say i did this incorrectly and invalidates warranty. Any advice?
As an update my third motor lasted 16 months, which is better, until bearing went and Boche said they will send replacement, fourth motor in 2y 7m. Am pleased with ( so far) rolling warranty but replacements are slow.

 

[Beekeeper]

I got my third motor and have 10 months warranty left. This motor is lasting much better than previous two. Whilst it sounds OK there may be damage so don't want to replace seal in case Bosch say i did this incorrectly and invalidates warranty. Any advice?

what happened to the last 2 motors? What went wrong?

 

[maker]

what happened to the last 2 motors? What went wrong?

One starting graunching after 6 months which Bosch said was water ingress. The second kept cutting out which Bosch thought was software but couldn't figure how, so a new motor, though that was starting to graunch too. My third one is not graunching but does whine more. Living in Wales water is thrown up from wet ground and mud that collects behind chainring.

 

[Beekeeper]

One starting graunching after 6 months which Bosch said was water ingress. The second kept cutting out which Bosch thought was software but couldn't figure how, so a new motor, though that was starting to graunch too. My third one is not graunching but does whine more. Living in Wales water is thrown up from wet ground and mud that collects behind chainring.

That’s a bit unlucky. What’s your cleaning technique around the motor area?

 

[maker]

That’s a bit unlucky. What’s your cleaning technique around the motor area?

A dribble of water through a hose with soft car cleaning brush attached. The bike suffers a stronger spray from cycling on wet ground. On my third motor I use a soft brush to remove mud from behind the chainring as I read that could get forced through the seal.

 

[Beekeeper]

exactly, keep it well greased (maintained) and dry, no problem. But un-greased, wet or dirty and that’s when the problems start.

When I fit a rubber seal, I pack the back of the seal with tacky grease and also the bridge between the two lips of the seal.

hi bearing man,

just out of interest and for future reference is it possible to fit the Bosch drive side service kit with the motor still attached to the bike or would this be a bad idea? I realise that any dirt dropping in from the bike would be a disaster but is it possible?

 

[mick ol]

I have posted this on the general forum in the hope of reaching as many Bosch powered bike owners as possible.
About a year to 18 months ago, Bosch started supplying and fitting a felt seal. It fitted behind the circlip on the right hand side of the crankshaft, in the space between the crankshaft and the sprocket carrier. The idea was to protect the right hand crankshaft bearing from dirt and water ingress. This would be fine, if this part was well maintained and fitted to a road bike. Off road is a completely different story.

We are seeing some big issues on motors fitted with this felt seal. The felt is acting as a sponge and retaining water against the very bearing it was designed to protect. In the case below it has allowed enough water past to destroy the large clutch bearing and freewheel bearing surface too. It is also badly rusting the crankshaft, making the motor very difficult to get apart. If the felt is oiled or greased, it catches the grit and dirt and becomes a scouring pad, wearing into the crankshaft or soft aluminium sprocket carrier.

In the first set of images, you can see that this was not an old motor, the plastic gears are in excellent condition but the motor was almost destroyed.
In the second set of images, you can see a soaked felt that we pulled out after 1 month and it has already become sand paper!

If you own a Bosch powered mountain bike manufactured between 2015 and 2019 it will be fitted with this Gen 2 motor (no it's not a Gen 3, they were only fitted to road bikes and a few gravel bikes. Small chainring Gen 2). And if you have had a Bosch service kit or a new motor fitted within the last year to 18 months, check that this seal has not been fitted.

If you have had any work done by us at Performance Line Bearings, we have always refused to fit this part, preferring to fit our double lip rubber seal. But sadly it was in the BDU2xx service kits that we sold and may have been used by others.

There was a very good reason why the automotive industry stopped using felt seals back in the 50's!


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could i just pick the felt ring out as i can feel that it is slowing the pedals and causing resistance as my wifes bike hasnt it fitted and the pedals spin much more easily ,do you have the mudstops in stock .thanks mick

 

[Beekeeper]

A dribble of water through a hose with soft car cleaning brush attached. The bike suffers a stronger spray from cycling on wet ground. On my third motor I use a soft brush to remove mud from behind the chainring as I read that could get forced through the seal.

whenever I put a new chain on I reverse the front sprocket or put a new one on. I also fit new seals to the drive side but I make sure I pack Bosch green tacky grease behind the seals. It would take a lot for water to get past this thick grease as I stuff so much of it in.

fortunately I’ve only had a couple of very wet or muddy rides. We have 2 bikes with the Bosch Gen 2 motor and they have both done over 2000 miles. No issues yet.

 

[Bearing Man]

hi bearing man,

just out of interest and for future reference is it possible to fit the Bosch drive side service kit with the motor still attached to the bike or would this be a bad idea? I realise that any dirt dropping in from the bike would be a disaster but is it possible?

It would be perfectly possible to fit this kit in most cases. A tooth brush around the frame and motor area will normally get it clean enough. There are certain bikes where the frame will not allow access the some of the fasteners and in this case the motor would require removal. The tricky part at the moment id

 

[Bearing Man]

could i just pick the felt ring out as i can feel that it is slowing the pedals and causing resistance as my wifes bike hasnt it fitted and the pedals spin much more easily ,do you have the mudstops in stock .thanks mick

Yes, just remove the circlip and pick the felt seal out with a suitable tool. Yes, we always have MudStops in stock The MudStop will not cause friction, but our double lip rotary shaft seal that replaces the felt will cause some friction, but it will also work a dam sight better than felt.

 

[Bearing Man]

I got my third motor and have 10 months warranty left. This motor is lasting much better than previous two. Whilst it sounds OK there may be damage so don't want to replace seal in case Bosch say i did this incorrectly and invalidates warranty. Any advice?

If you have a Trek Powerfly, or Haibike, or some form of chain guide or anti chain suck device fitted? These can all help cause short term failure. If you can, fit a 17 or 18 tooth sprocket to allow the mud a better chance of falling away before it is compacted by the chain and forced under the Bosch seal. Scrape the back of the sprocket with a small pick or screwdriver to save brushing and sprinkling this area.


As above, you can see that with a small sprocket (14 / 15 tooth) there is nowhere for the mud to go. The chain will compress this mud with all your weight on the pedal + an extra 300%+ from the motor...It's enough to force this mud straight through the main motor bearing and into the motor!
This customer came in because the crankshaft bearing had failed (no crankshaft seal was fitted). Fortunately he did have a MudStop fitted and when we removed it, we found a clean well greased main motor bearing behind. WARNING! If you leave this mud to build up behind the sprocket for long enough, even a MudStop may not be able to hold it back.

 

[Beekeeper]

If you have a Trek Powerfly, or Haibike, or some form of chain guide or anti chain suck device fitted? These can all help cause short term failure. If you can, fit a 17 or 18 tooth sprocket to allow the mud a better chance of falling away before it is compacted by the chain and forced under the Bosch seal. Scrape the back of the sprocket with a small pick or screwdriver to save brushing and sprinkling this area.
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As above, you can see that with a small sprocket (14 / 15 tooth) there is nowhere for the mud to go. The chain will compress this mud with all your weight on the pedal + an extra 300%+ from the motor...It's enough to force this mud straight through the main motor bearing and into the motor!
This customer came in because the crankshaft bearing had failed (no crankshaft seal was fitted). Fortunately he did have a MudStop fitted and when we removed it, we found a clean well greased main motor bearing behind. WARNING! If you leave this mud to build up behind the sprocket for long enough, even a MudStop may not be able to hold it back.

View attachment 62253

how can you tell which of the 2 bearings have failed when you turn the crank. Presumably they would both make a grinding noise so how could you determine if it is the main bearing or crankshaft bearing?

 

[Bearing Man]

how can you tell which of the 2 bearings have failed when you turn the crank. Presumably they would both make a grinding noise so how could you determine if it is the main bearing or crankshaft bearing?

Good question, turning the crank forward will turn the crankshaft bearings and the main motor bearing, so if you have a noise like a coffee grinder by turning the cranks forward, it's a good sign that the main motor bearing requires immediate replacement. If you turn the crank backwards and still have a slight growling or rumbling noise, your crankshaft bearings are failing and your motor is in distress. For the crankshaft bearings to fail usually shows that water is now entering the motor and needs immediate attention.

 

[Beekeeper]

Good question, turning the crank forward will turn the crankshaft bearings and the main motor bearing, so if you have a noise like a coffee grinder by turning the cranks forward, it's a good sign that the main motor bearing requires immediate replacement. If you turn the crank backwards and still have a slight growling or rumbling noise, your crankshaft bearings are failing and your motor is in distress. For the crankshaft bearings to fail usually shows that water is now entering the motor and needs immediate attention.

Thanks, that makes sense.

How does debris actually enter the crankshaft orifice where the circlip sits?
The crank and pedal is screwed onto it and covers it completely. How does anything get in?

 

[Bearing Man]

Thanks, that makes sense.

How does debris actually enter the crankshaft orifice where the circlip sits?
The crank and pedal is screwed onto it and covers it completely. How does anything get in?

The crank tightens, or should tighten just as it touches the circlip and this leaves quite a big gap around the crankarm for water and debris to enter.

 

[Calsun]

Amazing that the German engineers could screw up this badly. The bike I built in 1973 had a sealed Phil Woods bottom bracket and it still performs flawlessly after many thousands of miles and who knows how many crank rotations. I do have to wonder if the Yamaha drives are better sealed against the elements.

 

[TheRealPoMo]

Well you've prompted me into action. I like to think I've been super careful...not checked yet.
For any other Aussies here, I contacted the local distributor and he can provide both Mudstop and crankshaft seal for about $70. They are not in stock, so 14 days. If anyone else wants them, best order now so he can get enough shipped from UK.
I thought maybe my clutch bearing was a worry as I only get noise on freewheel, but I thought I always did from day 1. Any comments @Bearing Man ?

 

[Bearing Man]

Amazing that the German engineers could screw up this badly. The bike I built in 1973 had a sealed Phil Woods bottom bracket and it still performs flawlessly after many thousands of miles and who knows how many crank rotations. I do have to wonder if the Yamaha drives are better sealed against the elements.

Nope! And the latest Yamaha motor (Same motor in the Giant), specifically designed for eMTB's, the PW-X and X2 are the worst of all Yamaha motors... Very odd?

 

[Bearing Man]

Well you've prompted me into action. I like to think I've been super careful...not checked yet.
For any other Aussies here, I contacted the local distributor and he can provide both Mudstop and crankshaft seal for about $70. They are not in stock, so 14 days. If anyone else wants them, best order now so he can get enough shipped from UK.
I thought maybe my clutch bearing was a worry as I only get noise on freewheel, but I thought I always did from day 1. Any comments @Bearing Man ?

Who is your local distributor? We manufacture the seal, so just wondering? Noise on freewheel would be odd as the motor stops completely and just the rear cassette starts to feewheel? The motor only uses its internal "freewheel" when you back pedal.

 

[SupasafeElectroLumberjack]

thanks for this info.

2 questions-
removal of felt ring- I presume it has to be replaced with an alternative part rather than just remove it and carry on
if an alternative part has to be fitted such as your mudstop, will fitting this personally void the warranty? If no, are they easy to fit?

Thanks

 

[Bearing Man]

Yes, you can find out all about an alternate seal here: Rotary shaft seal for Bosch And yes it's relatively easy to fit. Below are the instructions for both seal and MudStop.
These are external parts and will not affect any warranty. Not that there are many Gen 2's still in warranty.

 

[TheRealPoMo]

Who is your local distributor? We manufacture the seal, so just wondering? Noise on freewheel would be odd as the motor stops completely and just the rear cassette starts to feewheel? The motor only uses its internal "freewheel" when you back pedal.

Your distributor @Bearing Man. Carbon Lab Services in Gunalda.

The noise is probably fine then... could be something else. Cheers.

 

[SupasafeElectroLumberjack]

Yes, you can find out all about an alternate seal here: Rotary shaft seal for Bosch And yes it's relatively easy to fit. Below are the instructions for both seal and MudStop.
These are external parts and will not affect any warranty. Not that there are many Gen 2's still in warranty.

Thanks for this

Just had mine replaced under warranty, must be one of the last ones fitted to a bike sold new last year!

they come with a 2 year warranty though right?

So to confirm:
removal of the felt will not affect warranty (I find this hard to believe?)
the alternative, replacement part is fitted externally and fitment of this will not affect warranty either

 

[Bearing Man]

Thanks for this

Just had mine replaced under warranty, must be one of the last ones fitted to a bike sold new last year!

they come with a 2 year warranty though right?

So to confirm:
removal of the felt will not affect warranty (I find this hard to believe?)
the alternative, replacement part is fitted externally and fitment of this will not affect warranty either

They used to come with a rolling 2 year warranty but I believe this is now been stopped.

The MudStop does the same, you remove the original Bosch seal and replace it with the MudStop, this was sanctioned by Bosch and has definitely never affected anyone's warranty that I am aware of.

 

[SupasafeElectroLumberjack]

They used to come with a rolling 2 year warranty but I believe this is now been stopped.

The MudStop does the same, you remove the original Bosch seal and replace it with the MudStop, this was sanctioned by Bosch and has definitely never affected anyone's warranty that I am aware of.

yikes, I really hope you're wrong. Just emailed Bosch about this.

OK, good to know about the Mudstop thank you.