WARNING! To Bosch powered ebike owners (pre 2020)

[Daev]

@Bearing Man - well, false starts and hiccups aside, definitely think this needs doing - many thanks. I'm now about to put an Sram 18t sprocket on. However, the 14t seems to have a 3mm offset for some reason whereas the 18t doesn't. Also, if I ditch the cover, how do I secure the sprocket in place ?. I need to clean it all up properly and observe. It's dark here now and can barely see what I'm doing.
The 14t sprocket has no label on it so can't i.d. what to look for.

Check this muck out! - 350 miles, eh?

View attachment 80402 View attachment 80401

I think I've decided to just get a lock ring, clean up the existing 15t chain ring and use that, dump the chain guard ( thus giving room to clean it out properly). I'll install the mud stop and seal . This should keep the computers stuff happy by not increasing size of chain ring, while allowing a way for the mud/crap to get out and the seals should keep it all waterproof.
I'm happy with the gear ratios at the moment, so I'll see how it all goes for a few months and track down a new chain ring in the future if required.

@Bearing Man - in the meantime, I bought both greases from you ( just in case) which one do I use for the mud stop and seal jobs ?
Cheers

 

[Bearing Man]

Hi Bearing Man. Thanks for your input. Do you have a video or written guide on how to do this? I skimmed through the Bosch videos you have but it didn't seem like any of them were applicable.

I posted the PDF instructions in this thread 6 posts up from your original question on page 3.

 

[Bearing Man]

I think I've decided to just get a lock ring, clean up the existing 15t chain ring and use that, dump the chain guard ( thus giving room to clean it out properly). I'll install the mud stop and seal . This should keep the computers stuff happy by not increasing size of chain ring, while allowing a way for the mud/crap to get out and the seals should keep it all waterproof.
I'm happy with the gear ratios at the moment, so I'll see how it all goes for a few months and track down a new chain ring in the future if required.

@Bearing Man - in the meantime, I bought both greases from you ( just in case) which one do I use for the mud stop and seal jobs ?
Cheers

All your problems are being caused by the plastic bit around the front of your sprocket, did you remove it? The sprocket you need is a "Boost" sprocket, this will have the return on it. BBB Boost sprocket
"Boost" sprockets help spread the sprocket load on the carrier or 'boss' and stop the sprocket cutting through the soft aluminium. Also when mud gets packed down the back of the sprocket, the return helps deflect some of the pressure.
When mud is compressed down the back of the sprocket, if not cleared out, it will overpower the MudStop. This is why the bigger sprocket is also better, as mud is less likely to be able to build-up on a higher sprocket, it tends to crumble away. You can leave the chainguard (nut) as mud compressing against this will do no harm (although should still be raked out from time to time).
MOST IMPORTAINT thing of all, get rid of the plastic around your sprocket! This can kill a motor within 150 miles in muddy conditions.

 

[Bearing Man]

I think I've decided to just get a lock ring, clean up the existing 15t chain ring and use that, dump the chain guard ( thus giving room to clean it out properly). I'll install the mud stop and seal . This should keep the computers stuff happy by not increasing size of chain ring, while allowing a way for the mud/crap to get out and the seals should keep it all waterproof.
I'm happy with the gear ratios at the moment, so I'll see how it all goes for a few months and track down a new chain ring in the future if required.

@Bearing Man - in the meantime, I bought both greases from you ( just in case) which one do I use for the mud stop and seal jobs ?
Cheers

The green "Bosch long life Tacky Grease" should be used for the seal and MudStop. The MudStop should also be removed and re-greased every 3 to 4 months, depending on terrain and cleaning regimes.

 

[Daev]

All your problems are being caused by the plastic bit around the front of your sprocket, did you remove it? The sprocket you need is a "Boost" sprocket, this will have the return on it. BBB Boost sprocket
"Boost" sprockets help spread the sprocket load on the carrier or 'boss' and stop the sprocket cutting through the soft aluminium. Also when mud gets packed down the back of the sprocket, the return helps deflect some of the pressure.
When mud is compressed down the back of the sprocket, if not cleared out, it will overpower the MudStop. This is why the bigger sprocket is also better, as mud is less likely to be able to build-up on a higher sprocket, it tends to crumble away. You can leave the chainguard (nut) as mud compressing against this will do no harm (although should still be raked out from time to time).
MOST IMPORTAINT thing of all, get rid of the plastic around your sprocket! This can kill a motor within 150 miles in muddy conditions.

Again, many thanks for all that, very much appreciated.
After a steep learning curve of a weekend, I've removed the plastic chain guard attached to the engine casing entirely. It fell in half anyway - see pic.
I have secured the gear cable to the engine casing, see pic, with clips.
I've learned about sprocket offsets and ordered a Miranda chainring 3mm offset, 18t, boost, so that should be fine.
About to start work on the seals, thanks for the info re which grease to use.
Cheers

 

[Daev]

Bosch gen2 - slowly, slowly catchee monkey...... Well, I'm getting there but every step of the way has a challenge in it {sigh, i know, I know}
Anyway, in the comprehensive instructions provided by @Bearing Man , it says to remove the original Bosch bearing cover and discard - there's pictures and everything for the hard of thinking (i.e., me).
Now I looked and poked and prodded and everything and I couldn't see this bearing cover so assumed it hadn't got one..... so I ended up trying to coax the mudstop in with extreme prejudice. This isn't what it's designed for so it objected by splitting (d'oh).
Later on during a conversation with Pete, he gently explained to me that I hadn't got a unique motor that was half a mil bigger than all the rest, it was the original bearing seal preventing the mudstop from sliding home on the shaft.
Well, I prodded and poked, still couldn't see it, worked my way round the shaft and all of a sudden there was the tiniest bit of movement - well, waddaya know!??! - there was a seal after all. Couldn't believe how big it was when I finally managed to tease it out, and the fact that I hadn't been able to see it. When you know, you know.
Anyway, attaching a couple of pics for future reference and remember rule #1 - if it ain't going in, there's something in the way!!! - it should just push home with finger pressure - no big 'ommers required {ahem!}

 

[RustyMTB]

Many thanks @Bearing Man

 

[Daev]

. ....aaaaaand it's done

Mudstop, bearing seal, 18t chainring, and still enough room on the chain Rides like a dream.
Can't wait to try it out on the trails.

Thank you, thank you, thank you @Bearing Man for all your sound advice, patient guidance and awesome product.
Here's to many more happy hours from my Bosch Gen2 motor

 

[Daev]

. ....aaaaaand it's done

Mudstop, bearing seal, 18t chainring, and still enough room on the chain Rides like a dream.
Can't wait to try it out on the trails.

Thank you, thank you, thank you @Bearing Man for all your sound advice, patient guidance and awesome product.
Here's to many more happy hours from my Bosch Gen2 motor View attachment 80777

Been out for a quick ride round the woods - brilliant!! Piece of cake to keep the crank/ motor clear now ( see pic) thanks again @Bearing Man , and the 18t cog is a definite improvement.
Nothing fell off the bike except me!!... but panic not, I managed to cushion the bike with my body ( luckily )

 

[jarnof]

Installed cranksaft seal for bosch gen2, i can feel littlebit of friction when i spin crank on repair rack, is there any experience is this affecting battery life? and if ever i want to take it out how does it work or is there a need for it?

 

[Bearing Man]

Installed cranksaft seal for bosch gen2, i can feel littlebit of friction when i spin crank on repair rack, is there any experience is this affecting battery life? and if ever i want to take it out how does it work or is there a need for it?

Hi Jarnof, There should not be noticeable friction once the seal is fitted. When fitting the seal, Bosch long life "tacky" grease (or the like) should be applied liberally to the 'lips' of the seal and ideally a little behind the seal. A little lubrication on the outer surface of the seal can also help. There are a couple of things that can go wrong and cause friction though.
1, If no grease is used there will be friction and the seal will be hard to fit.
2, If air gets trapped behind the seal, it can rub on the crankshaft circlip and create drag. (the little bit of wire is with the seal to let the air out while being fitted)
3, Sometimes the inner seal lip can catch in the crankshaft circlip grove and flip under the outer seal lip and get stuck. This will create noticeable friction. This can be sorted out by removing the crankshaft circlip and using a small blunt screwdriver, carefully poke the seal lip back into where it should be.

It is possible to remove the seal and re-fit it, but this is not easy to do without damaging it while the motor cover is on the motor. It is relatively easy to remove the seal if you remove the motor cover from the motor.

You can do away with this seal altogether if you ride 100% on road, it's not necessary. However, if you ride off road, it is essential and will definitely help save your motor from bearing damage and water ingress.

 

[Zimmerframe]

Hi Jarnof, There should not be noticeable friction once the seal is fitted. When fitting the seal, Bosch long life "tacky" grease (or the like) should be applied liberally to the 'lips' of the seal and ideally a little behind the seal. A little lubrication on the outer surface of the seal can also help. There are a couple of things that can go wrong and cause friction though.
1, If no grease is used there will be friction and the seal will be hard to fit.
2, If air gets trapped behind the seal, it can rub on the crankshaft circlip and create drag. (the little bit of wire is with the seal to let the air out while being fitted)
3, Sometimes the inner seal lip can catch in the crankshaft circlip grove and flip under the outer seal lip and get stuck. This will create noticeable friction. This can be sorted out by removing the crankshaft circlip and using a small blunt screwdriver, carefully poke the seal lip back into where it should be.

It is possible to remove the seal and re-fit it, but this is not easy to do without damaging it while the motor cover is on the motor. It is relatively easy to remove the seal if you remove the motor cover from the motor.

You can do away with this seal altogether if you ride 100% on road, it's not necessary. However, if you ride off road, it is essential and will definitely help save your motor from bearing damage and water ingress.

90% of that could probably be posted somewhere else on the internet and you'd be rich beyond your wildest dreams !

 

[Jackware]

90% of that could probably be posted somewhere else on the internet and you'd be rich beyond your wildest dreams !

How did I know the angle you were going to take, even before I'd read your reply

 

[RustyMTB]

Zimhub.

X Frame.

 

[RustyMTB]

So as not to start a new thread, what do you reckon to this @Bearing Man ? Something or nothing?

 

[Bearing Man]

No problem. There is a little backlash in the freewheel mechanism and a little in the transfer gears and this is what you see here.

 

[RustyMTB]

Phew. Thanks Pete.

 

[RustyMTB]

Pete, I'm thinking about getting round to changing the bearing covers along with the clean & regrease. The actual process itself is no problem but I'm wondering about the frequency in general terms for the greatest benefit.

Since it's been so dry this year, I've thought leave it until the weather turns, then I'll have fresh covers for winter & the best possible chance for keeping water out but after that for a typical UK trail hacker?

 

[Bearing Man]

Unfortunately, this will always depend on the type of terrain you ride (dusty, sandy, muddy, a bit of everything! etc.) Also, this question is very dependant on your cleaning habits (after every ride, occasionally, never. With a hose, with a pressure washer, with a cloth, etc.). How you transport your bike (never, on a rack, in a van, etc.) How many miles a month and at what time of year (maybe 500 miles in the summer and 10 in the winter?) So, personally, I would start at 2 months, if the grease looks good, give it 3 months next time. If the grease looks dirty or has gone! give it 1 month and so on. Maybe during summer leave a little longer than winter etc. It's going to be a suck it and see exorcise I'm afraid.

 

[RustyMTB]

That's great detail, thanks very much.

 

[RustyMTB]

Well 50% of that went great. The drive side bearing cover more or less fell out, the other one though just will not budge. No amount of levering on the outer dust cover will move the seal cover (yes I removed the circlip!) I've had to admit defeat & reassemble. All suggestions welcome.

 

[RustyMTB]

Persisted & got it done. That thing was stuck in there good. There wasn't a lot pf grease left in either side, so the timing was good & whoever designed the driveside circlip is a knobjangler.

 

[Bearing Man]

"whoever designed the driveside circlip is a knobjangler."

Too true! I have to do loads of these and once your pliers have slipped once, and take the edge off the clip, you're in a world of frustration!

 

[RustyMTB]

I cannot for the life of me see the design benefit in having it bevelled inwards, just makes it so awkward to grip! Cheers Pete for the help with this, good of you to give your time & I would advise anyone running a Bosch CX4 to make this part of their care regime with of course, the service kit from the Ebike service centre.

 

[Beekeeper]

Unfortunately, this will always depend on the type of terrain you ride (dusty, sandy, muddy, a bit of everything! etc.) Also, this question is very dependant on your cleaning habits (after every ride, occasionally, never. With a hose, with a pressure washer, with a cloth, etc.). How you transport your bike (never, on a rack, in a van, etc.) How many miles a month and at what time of year (maybe 500 miles in the summer and 10 in the winter?) So, personally, I would start at 2 months, if the grease looks good, give it 3 months next time. If the grease looks dirty or has gone! give it 1 month and so on. Maybe during summer leave a little longer than winter etc. It's going to be a suck it and see exorcise I'm afraid.

Hi Bearing man, I wonder if you could help. My wife and I both have Cube 2019 bikes with the Bosch gen 2 motors. Bikes are almost the same but mine is higher spec (11 speed as opposed to her 10 speed) and my frame is larger.
During the usual yearly drive side seal changes and regreasing I noticed that the wife’s bike has a metal spacer when I remove the large lock ring but mine does not have a metal spacer. I just thought this was a bit odd as the bikes are the same age and motors identical. Any thoughts?

 

[Bearing Man]

Hi Beekeeper, this is a boost spacer for your front sprocket. If you are running 2.8 tyres, it should be behind the sprocket. If you have thinner tyres, it would usually go in front of the sprocket. It is used to help the chain past wider tyres.
It was not used on all bikes and depended in frame type, tyre size etc. It would be discarded if a "boost" sprocket was fitted with a 3mm return as part of the sprocket. As long as your chain is missing your tyre and your sprocket is tight once the lock ring is secured, I would't worry too much.

 

[Beekeeper]

Hi Beekeeper, this is a boost spacer for your front sprocket. If you are running 2.8 tyres, it should be behind the sprocket. If you have thinner tyres, it would usually go in front of the sprocket. It is used to help the chain past wider tyres.
It was not used on all bikes and depended in frame type, tyre size etc. It would be discarded if a "boost" sprocket was fitted with a 3mm return as part of the sprocket. As long as your chain is missing your tyre and your sprocket is tight once the lock ring is secured, I would't worry too much.

Thanks Bearing Man, that’s helpful. We both have 2.6 tyres on hardtails. Wife’s bike had not had seal changes for 2 years but it was clean as a whistle with plenty of green tacky grease still in place however my bike after only a year since the same service was fairly dry and I always apply the same amount of grease to both bikes and same new seals each time. I wondered if it was the ‘missing’ spacer on my bike that was causing the difference as we both ride in the same conditions. Perhaps the spacer was creating more room for debris to fall out and away from the bearing for example. Maybe it’s just a coincidence or perhaps riding style was the difference. Thanks again Bearing Man. I will check if there is any play in the front sprocket.

 

[Bearing Man]

Thanks Bearing Man, that’s helpful. We both have 2.6 tyres on hardtails. Wife’s bike had not had seal changes for 2 years but it was clean as a whistle with plenty of green tacky grease still in place however my bike after only a year since the same service was fairly dry and I always apply the same amount of grease to both bikes and same new seals each time. I wondered if it was the ‘missing’ spacer on my bike that was causing the difference as we both ride in the same conditions. Perhaps the spacer was creating more room for debris to fall out and away from the bearing for example. Maybe it’s just a coincidence or perhaps riding style was the difference. Thanks again Bearing Man. I will check if there is any play in the front sprocket.

If the spacer is fitted behind the front sprocket, or a "boost" sprocket is fitted with the lip facing inwards, your thoughts are spot on. What happens is mud gets compressed down the back of the sprocket by the chain. This compression is powerful enough to force mud between the sprocket boss and MudStop, but if it hits that metal washer first, it can sometimes slow it down.
If you're running a 14 or 15 tooth sprocket, think about trying a 17 or 18 tooth. This will help the mud collapse away when it is being compressed, it will also make your rear cassette last longer!

 

[RustyMTB]

Out of curiosity & a pathological maintenance habit, I went back in to the bearing seals today to see how things are doing in there. The bearing covers are doing their job as you'd expect, being newish & all but behind the outer seals, the grease had dispersed much more than I bargained for, bearing in mind I was last here only six weeks ago.

Quick clean & regrease & off we go again but will definitely keep an eye on this with the wet months coming in fast.

 

[RustyMTB]

@Bearing Man Pete, can you recommend a pair of pliers for removing the drive side circlip on the Gen 4? I've just given up after an hour trying, mine just ping off the bevelled ends.