All the gear, no idea!

[TommyC]

Hi all,

I got myself a 2022 cube stereo 140SL a few months ago. The idea was to replace my KTM enduro as I was fed up travelling so far just to be able ride the thing off road. So in that respect it’s been great.

I found this place while looking for a fix to my first problem. (Probably like most people who sign up!) the chain keeps jumping off the chainring when in a high gear. Already snapped a chain and made a mess of the chainring.



I’ve YouTube’d how to set the derailleur once I’ve replaced the chainring but now I’m struggling to find a 34T for my bosch gen4 motor. Can anyone suggest a decent chainring? Or is it worth buying a spider to open up options? It’s a 12 speed Shimano set up with a 52mm boost chainline (whatever that means!) should I also be replacing the chain regardless?

TIA

 

[Zimmerframe]

I take it you have the clutch on the derailleur turned on ?? (Apologies if stating the obvious ..)

 

[TommyC]

It’s only obvious if you know! But yeah the clutch is on.

 

[Mikerb]

So you need a chainring to fit the Bosch motor spindle ( which is the ISIS standard), 36t, 12 speed ( I assume) and boost. Boost refers to the 148mm width of the rear hub which is 6 mm wider than a standard 142mm hub equally distributed bothe sides. So the cassette is 3mm further out. A boost chainring will either be described as being 52mm chainline ( 49 mm being the standard width from the cntre of chain ring to the centre of the BB area) or +3mm.........49mm+3mm =52mm QED!
Try this one

Race Face Bosch Gen4 Direct Mount Chainring - SH 12-Speed - 52mm Chain Line - black (bike24.com)

 

[Streddaz]

Hi all,

I got myself a 2022 cube stereo 140SL a few months ago. The idea was to replace my KTM enduro as I was fed up travelling so far just to be able ride the thing off road. So in that respect it’s been great.

I found this place while looking for a fix to my first problem. (Probably like most people who sign up!) the chain keeps jumping off the chainring when in a high gear. Already snapped a chain and made a mess of the chainring.

View attachment 91889

I’ve YouTube’d how to set the derailleur once I’ve replaced the chainring but now I’m struggling to find a 34T for my bosch gen4 motor. Can anyone suggest a decent chainring? Or is it worth buying a spider to open up options? It’s a 12 speed Shimano set up with a 52mm boost chainline (whatever that means!) should I also be replacing the chain regardless?

TIA

If it is only jumping off on the higher gears (I assume you mean the smaller gears on the cassette?) it may be that the chain is too long and the derailleur is not able to keep the chain tight.
I would shift it into the hardest gear (smallest sprocket) and see how much tension there is on the chain. With modern wide/narrow front rings and chain guides, dropping a chain these days it fairly rare.
I also assume in your photo the chain guide is up to show the condition of the front chain ring?

 

[TommyC]

So you need a chainring to fit the Bosch motor spindle ( which is the ISIS standard), 36t, 12 speed ( I assume) and boost. Boost refers to the 148mm width of the rear hub which is 6 mm wider than a standard 142mm hub equally distributed bothe sides. So the cassette is 3mm further out. A boost chainring will either be described as being 52mm chainline ( 49 mm being the standard width from the cntre of chain ring to the centre of the BB area) or +3mm.........49mm+3mm =52mm QED!
Try this one

Race Face Bosch Gen4 Direct Mount Chainring - SH 12-Speed - 52mm Chain Line - black (bike24.com)

Thanks for the explanation and the recommendation. My current chainring is 34t. Am I right in thinking the 36t would shift all the gearing up a bit? If so that wouldn’t be so bad as I do feel like I run out of gears occasionally. What would this gearing change mean for the motor?

 

[TommyC]

If it is only jumping off on the higher gears (I assume you mean the smaller gears on the cassette?) it may be that the chain is too long and the derailleur is not able to keep the chain tight.
I would shift it into the hardest gear (smallest sprocket) and see how much tension there is on the chain. With modern wide/narrow front rings and chain guides, dropping a chain these days it fairly rare.
I also assume in your photo the chain guide is up to show the condition of the front chain ring?

yes the smaller gears on the cassette. When I changed the chain I fitted the exact same chain, cn-m6100, and took out links to match. I’m not really sure what the tension should look like on the chain? How much movement should there be?

 

[urastus]

yes the smaller gears on the cassette. When I changed the chain I fitted the exact same chain, cn-m6100, and took out links to match. I’m not really sure what the tension should look like on the chain? How much movement should there be?

It would be good if you could answer Streddaz other question. I haven't known a chain to come off the chain ring with thick / thin teeth and a chain guide fitted. So long as the chain is under tension, that part should be right. Did you have the chain guide fitted and was it fitted correctly? It will be something like the picture below. One other thing, did you fit the chain facing right way (text outside) and joining link facing right way (long side trailing).

 

[TommyC]

It would be good if you could answer Streddaz other question. I haven't known a chain to come off the chain ring with thick / thin teeth and a chain guide fitted. So long as the chain is under tension, that part should be right. Did you have the chain guide fitted and was it fitted correctly?

so the first time it happened I had removed the chain guide as it had come loose when out on a ride. But it’s happened multiple times since I refitted it, even with the new chain.
I noticed that it had bent the first chain and also a couple of the teeth on the chain ring. I’ve straightened the teeth out but they’re all so messed up now I fear it’s putting unnecessary wear on the new chain.

 

[urastus]

so the first time it happened I had removed the chain guide as it had come loose when out on a ride

there's one part of your problem I think. With the guide fitted correctly it's hard to see how the chain could come off. Consider; the chain came off because the chain guide was loose. Now the guide isn't there, the problem continues.

Still there is more at play here - the chain guide shouldn't come into play unless there are other things at fault too. You're problem looks like a cascade of small things.

Is the chain fitted correctly to the chain ring - consider the thick / thin teeth;
Chain guide fitted and correctly adjusted - use thread locker while you're at it.
Chain facing right way (text on outside)
Joining link facing right way - long hole trailing.
Derailer clutch activated and working.

There may be some outliers we can't see, for example a bent chain or a bent chain ring or a damaged tooth or a damaged link. If you believe all I've listed is good, then tip bike upside down and work through the gears. Look for anything that doesn't look right or sound right. If you think something is wrong but can't pick it, take a video where you think something isn't right.

 

[Zimmerframe]

the chain keeps jumping off the chainring when in a high gear

Does it jump off when you have the bike in a high gear and you're descending on rough terrain, or does if jump off when you're pedalling in the high gears ??

@e*thirteen Components any thoughts ?

 

[Tartam]

Hi all,

I got myself a 2022 cube stereo 140SL a few months ago. The idea was to replace my KTM enduro as I was fed up travelling so far just to be able ride the thing off road. So in that respect it’s been great.

I found this place while looking for a fix to my first problem. (Probably like most people who sign up!) the chain keeps jumping off the chainring when in a high gear. Already snapped a chain and made a mess of the chainring.

View attachment 91889

I’ve YouTube’d how to set the derailleur once I’ve replaced the chainring but now I’m struggling to find a 34T for my bosch gen4 motor. Can anyone suggest a decent chainring? Or is it worth buying a spider to open up options? It’s a 12 speed Shimano set up with a 52mm boost chainline (whatever that means!) should I also be replacing the chain regardless?

TIA

E*Thirteen

Our new direct mount e*spec chainrings use our new M3 narrow-wide tooth profile, which reduces weight without sacrificing chain-retention. In making our SL and UL chainrings lighter and more beautiful than their predecessors, we adapted a similar design to work with Bosch, Brose, Fazua and...

www.ethirteen.com

This one is (new model from them) very easy to install, and you can go up to 36, I did it (to my Rail 2022) and works smooth They have different sizes and for all types of motors.

 

[steve_sordy]

Is the mech spring keeping the mech arm tight? I had a problem recently with grass, crud, whatever clogging the mech (it could not be seen). This had the effect of increasing friction inside the mech such that the upper & lower mech arm were not keeping tension on the chain, even with the clutch off. At one point, the chain would touch the floor with the bike stationary. A slack chain is primed for an exit.

To fix, I removed the mech then dismantled and cleaned the whole thing, which is when I discovered the problem. I also found that the lower mech arm was slightly bent, the jockey wheels were not in line with each other and the b screw was not in contact (ie not doing anything). It's a wonder I had managed to finish my ride!

 

[emtbPhil]

What you need is a chainring with direct fit to bosch.

The e-thirteen ones are kinda hard to find at the moment - hope make a very nice one (which I recently upgraded to) and there's a barely used one for a bargain on ebay at the moment - Hope E-Bike Cycle Spiderless 34T Retainer Chainring 5056033499576 | eBay

That being said a few month old bike shouldn't drop a chain like that, and I'm not sure why you had to change the cassette.
My money would be on chain too long.

 

[Dannage]

Can you mount the bike in a stand so you can rotate the pedals by hand and see what the chain is doing as you go up and down the gears? You'll be able to get a better grasp of the problem like that. Then come back and tell us what you see and we can suggest solutions.

 

[Stihldog]

I I also found that the lower mech arm was slightly bent, the jockey wheels were not in line with each other and the b screw was not in contact (ie not doing anything).

The B screw and jockey wheel alignment was one of the first thing I thought, when I read this issue. But there’s lots of good suggestions that can easily be addressed.
I just installed an e-thirteen 34t on the Bosch gen4 but I didn’t know a 36t was possible on a Rail.

 

[Tartam]

The B screw and jockey wheel alignment was one of the first thing I thought, when I read this issue. But there’s lots of good suggestions that can easily be addressed.
I just installed an e-thirteen 34t on the Bosch gen4 but I didn’t know a 36t was possible on a Rail.

The new ones (36) are working flawless, no spacers/adapting or something else, just put them on and ride. Even the gear shifting was ok, I didn't need to adjust it. The chain where of course shorter and tighter and was wear/worn out in 2 months, after I put it on, but I was prepared for that and replace it.
No more problems like the (36) old ones, like damaging the frame or something else. I'm sure that even the 38 will fit/run well, but it's hanging too much out down the bottom and it's a risk that will be damaged on big chunky rocks (for me will surely do, where I ride).
Even Trek USA have them in online shop for components, so I think that they work well with almost all types of eMTB's .

e*thirteen Bosch Gen 4 Aluminum Direct Mount Chainring - Trek Bikes

Enhance your cycling experience with e*thirteen Bosch Gen 4 Aluminum Direct Mount Chainring. Shop now!

www.trekbikes.com

 

[Tartam]

I've bought mine + accessories from here, they ship worldwide.

e*spec Aluminium Direct Mount Bosch CX Chainring

Features - e*spec Aluminium Direct Mount Chainring Chainring for 11 and 12-speed Chain line 53mm (Boost) M3 narrow-wide tooth profile eliminates chain noise and decreases overall system wear Product features Use:...

www.bike-discount.de

Comp Crank Puller for Bosch Lockring (3. und 4. Gen)

Features - Lockring Tool for Bosch (3./4. Gen.) & Brose Slipping of the toothing is prevented For professional repair Even tightly fitting lock nuts can be easily removed Product features Use: Assembly and...

www.bike-discount.de

CWP-7 Crank Puller

Suitable for: Square taper Splined (ISIS Drive, Octalink) BNI (Bosch E-Bikes) Size : 11.3 mm 16.3 mm Scope of delivery : 1 x Park Tool CWP-7 Compact Universal Crank Puller

www.bike-discount.de

 

[TommyC]

Does it jump off when you have the bike in a high gear and you're descending on rough terrain, or does if jump off when you're pedalling in the high gears ??

@e*thirteen Components any thoughts ?

The chain comes off as soon as there is any load. It’s only coming off the chainring, not the cassette.

Is the mech spring keeping the mech arm tight? .

I’m pretty sure the mech does need looking at. I just wanted to get a new chain ring on first.

What you need is a chainring with direct fit to bosch.

The e-thirteen ones are kinda hard to find at the moment - hope make a very nice one (which I recently upgraded to) and there's a barely used one for a bargain on ebay at the moment - Hope E-Bike Cycle Spiderless 34T Retainer Chainring 5056033499576 | eBay

That being said a few month old bike shouldn't drop a chain like that, and I'm not sure why you had to change the cassette.
My money would be on chain too long.

I had considered the hope chainring but was really after a steel e-thirteen one due to the price. The new chain I fitted is the same length as the factory one I removed so unlikely to be too long? I haven’t changed the cassette, just the chain with an identical one.

Can you mount the bike in a stand so you can rotate the pedals by hand and see what the chain is doing as you go up and down the gears?

I’ve just invested in a stand so I do plan to do this when I get the time!

 

[emtbPhil]

I had considered the hope chainring but was really after a steel e-thirteen one due to the price. The new chain I fitted is the same length as the factory one I removed so unlikely to be too long? I haven’t changed the cassette, just the chain with an identical one.

Ok so the bike was standard and didn't have issues
You replaced just the chain and it started jumping off the chainring

If the bikes done a lot of mileage then the chainring could be worn causing it to jump out. But if it's a 2022 bike I doubt that?
Do you have the old chain? If so I'd put that back on for a ride to see if it stops doing it.
It could actually just be a slightly bent connector on the chain, I've seen that on a friends where it was bent in the post and kept jumping off.

 

[Mikerb]

just to note re a couple of the posts a bove .......the E 13 chainring fitted as original is not narrow wide so the chainguide is pretty important. I am not sure why Trek has entered the conversation re fitting a different size chainring. Going from 34 to 36 may not work on the Cube.....it depends how much clearance there is between the chainring and the chainstay.........and that is specific to each brands bike frame.
If you go from 34 to 36 the gearing with be higher across the range of gears and the chain will likely need to be 1 or 2 links longer.

 

[TommyC]

just to note re a couple of the posts a bove .......the E 13 chainring fitted as original is not narrow wide so the chainguide is pretty important.

are you certain about this? It looks narrow/wide to me? I’ve ordered a new hope chainring now anyways. Going to check the chain is nice and straight, buy a new one if not, then go through everything at once and see if anything becomes obvious.

 

[Zimmerframe]

are you certain about this? It looks narrow/wide to me? I’ve ordered a new hope chainring now anyways. Going to check the chain is nice and straight, buy a new one if not, then go through everything at once and see if anything becomes obvious.

It could be that with supply issues, they've put an 11t chainring on or just made an error on the whole batch. I know Focus did something similar last year and it resulted in lots of chains falling off and other issues.

 

[emtbPhil]

It absolutely 100% is narrow wide. It says so on the spec and mine is in my hand

 

[Mikerb]

are you certain about this? It looks narrow/wide to me? I’ve ordered a new hope chainring now anyways. Going to check the chain is nice and straight, buy a new one if not, then go through everything at once and see if anything becomes obvious.

It did not look like a narrow wide design to me.....could be wrong!! I am more used to SRAM/Eagle/Synch2 type chainrings than Shimano!

 

[Mikerb]

It absolutely 100% is narrow wide. It says so on the spec and mine is in my hand

OK thanks for the correction.

 

[emtbPhil]

are you certain about this? It looks narrow/wide to me? I’ve ordered a new hope chainring now anyways. Going to check the chain is nice and straight, buy a new one if not, then go through everything at once and see if anything becomes obvious.

just to check that you know - you need a Bosch gen4 lockring socket to remove it. It’s a special tool

The unior tool the cheapest and what I usehttps://activesport.co/epages/80c85f8f-7a95-4b1c-9c30-e64b314f3f2e.mobile/en_GB/?ObjectPath=/Shops/80c85f8f-7a95-4b1c-9c30-e64b314f3f2e/Products/UN-16069&Locale=en_GB

 

[TommyC]

It could be that with supply issues, they've put an 11t chainring on…

What do mean by 11t chainring? I’ve got a 1x12 drivetrain with 34t chainring and 10-51 cassette.

 

[TommyC]

just to check that you know - you need a Bosch gen4 lockring socket to remove it. It’s a special tool

I bought a cheap one off Amazon for £9!

 

[Zimmerframe]

Oops sorry, meant 11s (speed).