Bosch bearing seal regrease

[Beekeeper]

Front chainring was worn and would not work with new chain so I decided to flip it over to the other side.
While i was at it I removed the main motor bearing dust seal, used a paintbrush to remove dust. It was pretty dry in there.
applied Bosch green tacky grease. Fitted a brand new dust seal.

flipping the chain ring over seems to have worked well and I can now use a new chain. Been for a test ride and cassette working fine as well.

 

[Beekeeper]

Mrs Beekeeper’s chain has finally worn out at 1400 miles. Replaced front chainring also and fitted a new bearing seal

 

[Philly G]

is the seal just an o-ring? Where did you get the special Bosch grease?

 

[Beekeeper]

The seal is not an ‘o ring’. It’s a specially made part by Bosch that was introduced for the Gen 2 motor in later years to reduce the chances of water, dust ingress into the main bearing on the right hand side.

The grease is special Bosch green tacky grease which is different to the internal white grease inside the motor. This green stuff is more robust and stays in place longer. I’m sure there are cheaper alternatives but it’s not something I’ll be doing very often so I’m happy to use the expensive Bosch green stuff.

You can buy the seals and grease from Amazon. The seals come in packs of 5 but I really don’t see why you can’t just clean the old one and put it back. I suspect it’s to discourage people using a degreaser on it and putting back in place ?.
It does feel psychologically good however putting a brand new seal in place ?



I’ve completed this process with 2 bikes now and there was still some factory grease behind the seal and all looked fairly clean,

Once you take out the old seal (easy with a flat bladed screwdriver, just press down on one of the tabs and you can basically drag them out), I use several cotton buds to gently remove old grease and then add new grease all around the bearing and press a new seal in place. Make sure it is firmly in place. Wipe away any surplus grease that oozes out.

I see that the kit now comes with 5 felt seals also which fit on the crank behind the circlip. I’ve not used these felt seals yet but may try them in the future just as an experiment. I don’t really get the bike that wet or muddy but they may help prevent some dust / grit entering that location.

 

[Philly G]

Thank you for the thorough reply! I'm a firm believer in preventative maintenance

 

[deksawyer]

Thank you for the thorough reply! I'm a firm believer in preventative maintenance

You need the mudstopper and crankshaft seal from @Bearing Man then.

 

[Beekeeper]

Just for clarity, this thread is Gen 2 and Gen 3 specific.

Not applicable to Gen 4 ?

I’m only familiar with Gen 2 motors which have the small chainring. I’m not sure if the seals are better on the Gen 3 and 4 motors or even what type they are.
I suspect with the Gen 3 bikes they tend to be lower powered and not so ‘off road’ so perhaps get less of a hammering from the elements.

Maybe @Bearing Man might comment on the relative seal efficacy of all 3 types?

 

[Bearing Man]

I’m only familiar with Gen 2 motors which have the small chainring. I’m not sure if the seals are better on the Gen 3 and 4 motors or even what type they are.
I suspect with the Gen 3 bikes they tend to be lower powered and not so ‘off road’ so perhaps get less of a hammering from the elements.

Maybe @Bearing Man might comment on the relative seal efficacy of all 3 types?

Funny you should say this, just doing a Gen 3 today that's been full of water! Gen 4 seem a little better so far but watch this space.

 

[Beekeeper]

Looks horrid.
one thing I’ve always wondered from videos is the metal gear cluster in Gen 2 always seems to be dry as a bone. Presumably light gear oil would simply spray around and dilute the grease elsewhere?
And thick grease would add drag to those metal gears?
Maybe they do have lubrication of some sort? It can’t be dry metal on metal can it?

 

[Beekeeper]

Just for information if anyone chooses to go down the “felt ring route” for the crankshaft seal.
mine just arrived.

The felt ring has been factory fitted in the Bosch from “November 2019”. The purpose being to “increase the robustness of the drive unit”

Green tacky grease (supplied) is packed into the crank cavity and then the felt ring put on followed by the metal circlip. Diagram is below. You get a tube of grease, 5 felt rings and 5 circlips for this part.

However, The “fit and forget” crankshaft seal provided by @Bearing Man does seem a neater and less messy option in my opinion.

 

[Beekeeper]

Ok, the pack of seals just continued to stare at me from the table and as it was nice weather I decided to get on with the job. Only needed to remove the crank arm so a dead easy job taking just minutes.

1. remove circlip and clean cavity
2. Fill with Bosch magical green grease
3. Insert felt sealing ring
4. Insert new circlip
5. Sit back and enjoy a cup of tea and Mr Kipling Apple pie admiring your work in the proud knowledge that your bike is now more watertight than a nuclear submarine

 

[Bearing Man]

Please be warned, 98% of Bosch motors are fitted into road bikes. So felt seals are a poor but workable fix for these bikes. Fitting a felt seal into a moving component on a mountain bike is not a great idea! And if you don't maintain this seal with an OCD level of maintenance, you will stand a good chance of turning your felt seal into a brillow pad!

 

[Beekeeper]

Please be warned, 98% of Bosch motors are fitted into road bikes. So felt seals are a poor but workable fix for these bikes. Fitting a felt seal into a moving component on a mountain bike is not a great idea! And if you don't maintain this seal with an OCD level of maintenance, you will stand a good chance of turning your felt seal into a brillow pad!

I’m very OCD so don’t worry. In fact my consignment of Bosch tacky grease is on its way..

 

[Bearing Man]

I’m very OCD so don’t worry. In fact my consignment of Bosch tacky grease is on its way..

Wish you'd bought that from me, I could have retired!

 

[Beekeeper]

Wish you'd bought that from me, I could have retired!

Once the wife gets fed up with a green greasy monster coming into the house each day, I’ll order a couple of MudStops and crankshaft seals from you.

 

[Chris B]

This might be a stupid question, but how is the other side sealed? is it a good seal and needs no further work.

 

[Bearing Man]

This might be a stupid question, but how is the other side sealed? is it a good seal and needs no further work.

There is currently no seal option available for the left side although we are working on on that we hope will be ready for the winter.
We currently pack the gap between the bearing and the motor case with water resistant grease to ensure the longest best chance possible for the left hand crankshaft bearing.

 

[Fingerpuk]

Have just emailed you @Bearing Man so I can put an order in. My poor motor gets abused - I see deep mud and water and just think sod it.

When the rains come the thing will get a service.