Bosch CX Motor - Drivetrain Improvements

[Phil Dryden]

A little while ago I wrote a brief 1000 mile report on my Cube Kathmandu, and basically all was going extremely well. I molly coddle the bike, with no off road riding - stick to dry riding on roads and tarmac cycle paths. This made my findings below all the more surprising.

When I reached around 1300 miles I became aware of an additional sound to the drivetrain - a slight ‘chatter’ accompanied the normal electrical whine. Having heard so much about the infamous bearing problems with the CX motor, I fitted a new bearing seal kit to the RH crank. Whilst my 2018 bike was already fitted with the plastic castellated sealing ring, I was shocked to see that it was bone dry; not a trace of grease anywhere around it, none behind it or in front of it. I can’t believe that it would all have totally disappeared in 1300 miles, so it was evidently not packed with grease at the factory.

Anyway, I replaced the seal, packed it well with grease, but the noise was still there. A while later I decided to check my chain, and I was alarmed to see that the 0.75% wear gauge fitted easily between the links. I had not appreciated how much the CX drive wears the chain. I have now changed the chain, cassette, and chainring and thankfully the bike is purring along like a Rolls again.

I took the opportunity to replace the 15T chainring with an 18T ring. For anyone thinking of doing the same, I can confirm that it does move the bulk of the sprocket activity nearer the middle of the cassette, which is a good thing and also gives the equivalent of an extra gear at the top end for travelling at speed. The only downside is that its not possible to retain the plastic chain cover as the larger ring causes the chain to foul the lower plastic fixing for the guard. Pity, as the guard does give that vulnerable RH crank area some extra protection from the worst of the elements, but I can live without it.

Just to summarise, then. For CX motor users -

I strongly urge you to ensure there is ample grease around the castellated bearing seal, and check it regularly.

Check the chain at frequent intervals and replace early

The larger chainring is a great improvement, and worth the loss of the plastic chain guard.

 

[alexa]

Just wondering, was your bike still under warranty? and if so, did you remove the seals on the torx screws to get to the bearings?

 

[xena]

Very topical, I changed my 15t front sprocket to 18t yesterday, and have run into a couple of problems:
1, the chain is now too tight so I need a new one, but am not sure how to pick inte the right length
2, I now have a chatter/clicking from the front sprocket, I thought maybe due to a worn chain and new cog, but I'll check the guard. (ETA I don't think I have a guard, only the locking ring)

Mine is Cube CX with 11-42 10sp on the back.

 

[Andy-Mat]

A little while ago I wrote a brief 1000 mile report on my Cube Kathmandu, and basically all was going extremely well. I molly coddle the bike, with no off road riding - stick to dry riding on roads and tarmac cycle paths. This made my findings below all the more surprising.

When I reached around 1300 miles I became aware of an additional sound to the drivetrain - a slight ‘chatter’ accompanied the normal electrical whine. Having heard so much about the infamous bearing problems with the CX motor, I fitted a new bearing seal kit to the RH crank. Whilst my 2018 bike was already fitted with the plastic castellated sealing ring, I was shocked to see that it was bone dry; not a trace of grease anywhere around it, none behind it or in front of it. I can’t believe that it would all have totally disappeared in 1300 miles, so it was evidently not packed with grease at the factory.

Anyway, I replaced the seal, packed it well with grease, but the noise was still there. A while later I decided to check my chain, and I was alarmed to see that the 0.75% wear gauge fitted easily between the links. I had not appreciated how much the CX drive wears the chain. I have now changed the chain, cassette, and chainring and thankfully the bike is purring along like a Rolls again.

I took the opportunity to replace the 15T chainring with an 18T ring. For anyone thinking of doing the same, I can confirm that it does move the bulk of the sprocket activity nearer the middle of the cassette, which is a good thing and also gives the equivalent of an extra gear at the top end for travelling at speed. The only downside is that its not possible to retain the plastic chain cover as the larger ring causes the chain to foul the lower plastic fixing for the guard. Pity, as the guard does give that vulnerable RH crank area some extra protection from the worst of the elements, but I can live without it.

Just to summarise, then. For CX motor users -

I strongly urge you to ensure there is ample grease around the castellated bearing seal, and check it regularly.

Check the chain at frequent intervals and replace early

The larger chainring is a great improvement, and worth the loss of the plastic chain guard.

Interesting post, many thanks.
Mainly due to some of the points you mentioned, chain wear is a prime example, is why I have avoided this type of electric bike with the middle motor in the crank area.
Both of my bikes have had rear wheel motors and on those, chain wear is reduced in comparison.
OK, so I won't be exceeding any speed limits, but the occasional downhill run at 40 KMH, has put me off doing that on the flat anyway!
Also, local police , here I live, are nowadays starting to take interest in illegal e-bikes apparently.....as we are limited to 25KMH max.....around 15MPH.
I found your post very interesting, just to see how the other half live, so to say!
Have a great Sunday.
Andy

 

[georgehenry]

I have a 2011 old Oxygen rear hub drive bike that is still going strong and a real workhorse. The drive train on this bike lasts for what seems like forever, so long in fact that I cannot remember when I last changed it, and the bike itself has proved to be extremely robust. It is a simple cadence system with a throttle and three levels of assistance, and is a relaxing and very practical mode of transport. Although not designed for off road use, it came with lights, a rear rack and full mudguards, I have taken it to places it was not designed to go and it worked much better than expected, so it has not had an easy life.

In 2015 I bought a Yamaha powered Haibike hard tail mountain bike to enable me to ride to work cross country. That has also proved to be a very capable work horse too and having a more sophisticated display I have been able to keep an accurate record of the mileage that is now showing 11,324 miles. It is of course a crank drive torque controlled power delivery that shines off road where it can climb steep and difficult off road routes. However it wears the drive train an order of magnitude quicker than a rear hub system. I am as gentle changing gear as I can manage but it can still wear a chain and start to jump in the top gear smallest cog of the rear cassette in 1000 miles. The Yamaha system has a normal size front chain ring and a good quality narrow wide one will out last several chains and rear cassettes.

I have not recorded the mileage of my 2011 rear hub bike but it must me quite a bit more than the Haibike!

I really love both my bikes and their different operating systems for different reasons and they earn their keep by transporting me to work and back, a 20 mile round trip and also numerous local shopping trips and other errands like the library, dentist, doctor and many others. I am also a lot fitter as a result of riding a bike most days, and love the countryside I ride through on my off road and canal tow path journeys.

 

[Phil Dryden]

Just wondering, was your bike still under warranty? and if so, did you remove the seals on the torx screws to get to the bearings?

Hi Alexa,
Yes the motor is still under warranty; 1 year old, and I believe the warranty is for 2 years. None of the work I did requires access to the motor, and I certainly would not have attempted access while warranty is valid. The bearing seal kit plus grease can be done externally and is only intended to 'waterproof' the access to the motor bearings along the crank. It was, I believe, brought out as an after market kit, although new motors now come with it ready fitted (but no grease, apparently!)
The service parts are here:

Direct Car Parts : Car Accessories UK

Direct Car Parts offer a range of car parts and car accessories and supply customers around the UK.

www.the-ebikestore.co.uk

 

[Phil Dryden]

Very topical, I changed my 15t front sprocket to 18t yesterday, and have run into a couple of problems:
1, the chain is now too tight so I need a new one, but am not sure how to pick inte the right length
2, I now have a chatter/clicking from the front sprocket, I thought maybe due to a worn chain and new cog, but I'll check the guard. (ETA I don't think I have a guard, only the locking ring)

Mine is Cube CX with 11-42 10sp on the back.

I'm sure that if your CX is the same vintage as mine (mid 2018) it would have come with a black plastic chain cover that fits around the crank and is secured by 2 plastic clips to the motor cover and a metal bracket to the chainstay. I found that the 18T cog would clear the fixing clip ok, but when the cover was refitted it rubbed on the cover where it fits over the clip, so I left it off. I'm getting to like the new look, kinda cool and a bit edgy! If your chain is rubbing on the clip itself, then you might have to hacksaw off the little plastic clip.
Chain length!!!! That was the hardest part! I got one of these (I think)

X10EL 10-speed Chain

Features - KMC X10EL Connector Missing Link Double X-Durability For Shimano, Campagnolo and SRAM 10-speed derailleur systems Product features Use: MTB, Road Bike, Trekking Model: X10EL Dimensions: 1/2" X...

www.bike-discount.de

and reckoned I needed to take out 4 links. Was as tight as a drum when I refitted it. Snag was I could not rejoin it! Managed to find a spare split link and put the whole section back in which did the job, so I now have 2 split links which is not ideal, but hey ho life is not perfect! I shall be buying cheaper chains and replacing them more frequently to save the rest of the drivetrain and keep it all sweet.

 

[Phil Dryden]

Just found the box that the chain came in. It is a KMC X10 114 links, cost about £12.

 

[xena]

Just found the box that the chain came in. It is a KMC X10 114 links, cost about £12.

Yeah I'd already been eyeing one of them up as I could see that it was fitted as standard, but i wasn't sure of the length- they give you more links than you necessarily need then? Might replace my cassette at the same time.

 

[Phil Dryden]

Hi Xena,
I would try it as is comes, first. Then just take out a line at a time, testing after each one. Remember its impossible to get the things back in once taken out! The Tube video below gives a smart little tip for breaking apart a stubborn split link using ordinary pliers.

Cassette cost me around £27, and was a doddle to replace. Removed and cleaned jacket wheels at same time.

 

[xena]

Cheers Phil, it'll be my first chain change, so ta for the vid. Seems most things are doable with a bit of research and YouTube guidance!

 

[soundwave]

Cheers Phil, it'll be my first chain change, so ta for the vid. Seems most things are doable with a bit of research and YouTube guidance!

if you keep going to a lbs to get work done it soon gets expensive fast i never even remove a wheel b4 i got my bike and can now strip it all down and rebuild it all from watching you tube vids.

 

[Gadfly]

Very topical, I changed my 15t front sprocket to 18t yesterday, and have run into a couple of problems:
1, the chain is now too tight so I need a new one, but am not sure how to pick inte the right length

You have increased the sprocket size by three teeth so you need three extra links.