Over-torqued Motor Mount Bolts?

[SavvyPavvy]

Hey guys, I have a carbon frame e-bike that's recently developed a creaking noise by the bottom bracket that comes with every pedal stroke.
I regreased and reinstalled the pedals, cranks and even the seat, nothing seemed to work. Extremely annoying.

My next step was the motor mount bolts, I couldn't find documentation on what the torque specs were beyond a 2 page document that stated "20nm" for another similar ebike model (both carbon and aluminum), so in a sweaty irritated rush I took the bolts out, regreased and reinstalled.

First major dummy move, I had my wrench set to 20ft/lbs instead of 20nm, a whopping 27nm of torque. Next dummy move, I realized that 20nm itself was probably overkill for a carbon frame, upon further research it seems like general consensus is 11nm, not 20nm!

I immediately backed off and retorqued to 11nm and left it, and fortunately I didn't hear any cracking or detect any damage on the frame itself, but now I'm paranoid I've done myself in. I've recently reached out to the manufacturer to get the proper specs (what I should have done first), but I was curious to see what the folks here thought.

Here's an image of one of my mounts, they all seem "okay" but I'm no carbon expert.

Feel free to absolutely roast me in the comments

 

[RustyIron]

If I was a bettin' man, I'd put good money on your bike being ok.

 

[SavvyPavvy]

If I was a bettin' man, I'd put good money on your bike being ok.

Thanks, although I'm not much for gambling it seems like the manufacturer themselves state that the correct torque setting is actually 20nm +3nm or so, so perhaps I haven't screwed myself like I previously thought

 

[Mikerb]

A lot depends on how the bearings/bolts are mounted on the bike. Removing motor bolts is something I have never needed to do but if my bike was carbon ( well it would not be because there is no way I would buy a carbon MTB!!) I would hope that the bearings have a metal sleeve between them or better still are actually fitted into a metal sleeve bonded to the carbon access holes...either way so that the bolt head is not being tightened down onto an unsupported carbon shoulder.

 

[SavvyPavvy]

A lot depends on how the bearings/bolts are mounted on the bike. Removing motor bolts is something I have never needed to do but if my bike was carbon . I would hope that the bearings have a metal sleeve between them or better still are actually fitted into a metal sleeve bonded to the carbon access holes...either way so that the bolt head is not being tightened down onto an unsupported carbon shoulder.

Hah, when I ordered my bike I actually had no idea it was carbon, I've been out of MTB for so long I wasn't aware most top end bikes today are indeed carbon. If I had it my way I'd pick aluminum, but ah well

As far as I can see there isn't a metal sleeve, but instead there are carbon shoulders themselves reaching inwardly to the motor mounting surface and they seem quite robust, most are well over half an inch thick. Again, seems damage-free.

 

[Bummers]

Big problem with cube e-bikes failing here, they gave out wrong info and people were torquing to 20nm when it should have been 11. Get it in writing (email) from the manufacturer what the official figure is then double check that elsewhere!

 

[Mikerb]

Hah, when I ordered my bike I actually had no idea it was carbon, I've been out of MTB for so long I wasn't aware most top end bikes today are indeed carbon. If I had it my way I'd pick aluminum, but ah well

As far as I can see there isn't a metal sleeve, but instead there are carbon shoulders themselves reaching inwardly to the motor mounting surface and they seem quite robust, most are well over half an inch thick. Again, seems damage-free.

View attachment 144927 View attachment 144928

in which case the motor mount section is a cting as the sleeve which at least supports the carbon shoulders in terms of compression..............personally I would prefer metal sleeving anywhere on a carbon frame that is designed for a bolted fixing. Using the motor mount is fine until/unless the bolt comes loose! What you describe at least means you are unlikely to have caused any frame damage with excess torque............you may however have overstretched the bolt threads so I would keep an eye on them for a while.

 

[SavvyPavvy]

Big problem with cube e-bikes failing here, they gave out wrong info and people were torquing to 20nm when it should have been 11. Get it in writing (email) from the manufacturer what the official figure is then double check that elsewhere!

Manufacturer has confirmed it is indeed 20nm, so that's good as it seems like I was close enough.

 

[SavvyPavvy]

in which case the motor mount section is a cting as the sleeve which at least supports the carbon shoulders in terms of compression..............personally I would prefer metal sleeving anywhere on a carbon frame that is designed for a bolted fixing. Using the motor mount is fine until/unless the bolt comes loose! What you describe at least means you are unlikely to have caused any frame damage with excess torque............you may however have overstretched the bolt threads so I would keep an eye on them for a while.

You know what I actually reexamined the mounting area and it seems like they did put in metal inserts / threads for these mounting points. I know carbon doesn't take crushing forces all that kindly but I'd imagine this adds significant strength to the area. I'm leaning on the bike being A-OK

 

[MrPeaski]

Big problem with cube e-bikes failing here, they gave out wrong info and people were torquing to 20nm when it should have been 11. Get it in writing (email) from the manufacturer what the official figure is then double check that elsewhere!

I asked Cube this directly, as there is a lot of misinformation about their frames.
Indeed I have posted about NOT torquing to 20Nm but to 11 instead. Up until now, I have stuck to this when doing my own bike (2020 160 Action Team)

I got a reply from Cube stating that 20Nm is actually correct.

However, there is a bolt on each side close to the lower swing arm pivot that looks a bit fragile, so I'll continue to torque those to 11Nm, but the other 4 bolts will be at 20Nm

 

[alancube]

I have always been of the understanding that when torquing fixings it is done 'dry' as any lubrication applied to the threads can cause over tightening.
Unless otherwise stated.

 

[RustyIron]

I have always been of the understanding that when torquing fixings it is done 'dry' as any lubrication applied to the threads can cause over tightening.

There are very few circumstances where you'd want to assemble threaded fasteners dry. It's ok if you're a assembling patio furniture that you'll throw away in a few years, but not on a precision machine, like a mountain bike. Dry threads will result in erratic torque readings, galling, and corrosion. When using a lubricant, clamping pressure is increased, so the torque is adjusted accordingly.

Bottom line: Clean your threaded fasteners, apply anti seize, assemble.

There are a hundred articles you can read on the topic, but here's one:

Bolt Lubricant and Torque: A Comprehensive Guide – Hex Technology

www.hextechnology.com

 

[Bummers]

I asked Cube this directly, as there is a lot of misinformation about their frames.
Indeed I have posted about NOT torquing to 20Nm but to 11 instead. Up until now, I have stuck to this when doing my own bike (2020 160 Action Team)

I got a reply from Cube stating that 20Nm is actually correct.
View attachment 145052

However, there is a bolt on each side close to the lower swing arm pivot that looks a bit fragile, so I'll continue to torque those to 11Nm, but the other 4 bolts will be at 20Nm

Yep, further investigation into this found out that cube got the torque figures from Bosch and quoted those. Problem being it didn't take into account the mounts being carbon with a tiny useless insert.
Stick to 11.
Seen quite a few failures now on the cube fb site.

 

[Hattori-Hanzo]

Big problem with cube e-bikes failing here, they gave out wrong info and people were torquing to 20nm when it should have been 11. Get it in writing (email) from the manufacturer what the official figure is then double check that elsewhere!

I'm not disagreeing with you, rather looking at it from a different perspective, is it really a big problem.
From the thousands of bikes sold, remembering Cube is one of the largest brands and this frame is on a number of different specced models, I've only seen a handful of complaints about the motor mounts failing.

Has it been determined that the frame is at fault, either with the design, material or construction?

From the posts I've seen, the failures have occurred from the mounting bolts either working loose (breaking mounting holes) or being over torqued (crushing the carbon), which is a maintenance issue.

Should the bolts be correctly torqued and thread locked from the factory. Yes 100% but there will always be cases where this hasn't happened, human error.

Should the retailer selling the bike double check all bolts before sending a bike out. Yes, but it probably doesn't happen as much as it should.

Should owners be checking these bolts. YES.

I've seen the 11/20nm (and other) figures passed around the Internet so many times I'm starting to doubt either are true, internet whispers.
My thoughts are 11nm is the minium and 20nm is the maximum, maybe I'll go somewhere in-between.
The main takeaway is these bolts should be checked very regularly.

I'm sure there will be people who only use these bikes for weekend countryside rides and will never see a problem at all.
On the other hand, if you're sending it down black rated runs with huge jumps/drops 2–3 times a week, you might want to consider checking these bolts every ride.

Should Cube be held responsible for Joe public over or under torquing these bolts with their Chinese torque wrenches.
My Chinese wrench may read a lot different to your Snap-on wrench, and the number of videos I've seen of people either incorrectly using a torque wrench, or using the wrong torque wrench entirely (especially on low values) is mad.
Again, regular maintenance would minimise risk.

Like I say, I'm trying to look at this from a different perspective, I'm not disagreeing with you that there may well be an issue with the frames, (such is the case with Pole swing arms, seems there is a common failure point observed from peoples posts) but I'd like to see more evidence that the frame is at fault and not the human before condemning a company due to a handful of Facebook posts.

 

[Bummers]

I'm not disagreeing with you, rather looking at it from a different perspective, is it really a big problem.
From the thousands of bikes sold, remembering Cube is one of the largest brands and this frame is on a number of different specced models, I've only seen a handful of complaints about the motor mounts failing.

Has it been determined that the frame is at fault, either with the design, material or construction?

From the posts I've seen, the failures have occurred from the mounting bolts either working loose (breaking mounting holes) or being over torqued (crushing the carbon), which is a maintenance issue.

Should the bolts be correctly torqued and thread locked from the factory. Yes 100% but there will always be cases where this hasn't happened, human error.

Should the retailer selling the bike double check all bolts before sending a bike out. Yes, but it probably doesn't happen as much as it should.

Should owners be checking these bolts. YES.

I've seen the 11/20nm (and others) figures passed around the Internet so many times I'm starting to doubt either are true, internet whispers.
My thoughts are 11nm is the minium and 20nm is the maximum, maybe I'll go somewhere in-between.
The main takeaway is these bolts should be checked very regularly.

I'm sure there will be people who only use these bikes for weekend countryside rides and will never see a problem at all.
On the other hand, if you're sending it down black rated runs with huge jumps/drops 2–3 times a week, you might want to consider checking these bolts every ride.

Should Cube be held responsible for Joe public over or under torquing these bolts with their Chinese torque wrenches.
My Chinese wrench may read a lot different to your Snap-on wrench, and the number of videos I've seen of people either incorrectly using a torque wrench, or using the wrong torque wrench entirely (especially on low values) is mad.
Again, regular maintenance would minimise risk.

Like I say, I'm trying to look at this from a different perspective, I'm not disagreeing with you that there may well be an issue with the frames, (such is the case with Pole swing arms, seems there is a common failure point observed from peoples posts) but I'd like to see more evidence that the frame is at fault and not the human before condemning a company due to a handful of Facebook posts.

If you look at the carbon mount compared to other brands it's ridiculously thin. The pictures show how frail it is.
Yep, riding on canal paths you'll get many who never have a problem, but the same frame comes with 170mm fox 38 forks with 160mm rear travel, full on enduro.

 

[Hattori-Hanzo]

I agree, to my untrained eyes it does look thin, however I'd really hope that Cube put some R&D into the mounting system to ensure it was adequate before releasing the bikes. I believe the newer 155 uses the same design?

I'd be interested to see how it compares to other brands with similar design.

I also agree it could be a concern that they use the same frame from trail bikes all the way through to enduro, maybe their claims of the hard hitting enduro range are coming undone.

 

[Bummers]

I agree, to my untrained eyes it does look thin, however I'd really hope that Cube put some R&D into the mounting system to ensure it was adequate before releasing the bikes. I believe the newer 155 uses the same design?

I'd be interested to see how it compares to other brands with similar design.

I also agree it could be a concern that they use the same frame from trail bikes all the way through to enduro, maybe their claims of the hard hitting enduro range are coming undone.

Looking at mondraker it's far more beefy and better built!

It seems that's how cube gets the best price point for their bikes, cheap out with the Chinese carbon frames.

 

[Spiff]

Bosch motor is normally assembled to frame using the Bosch Assembly plates, so there are two different Torque values:
** Bolts for Bosch Assembly Plates to Motor: Torque 8Nm
** Bolts for Bike Frame to Bosch Assembly Plates: Torque 20Nm

I got a couple Bosch PDF manuals that show these values for motor BDU450, which is the Performance Line CX 2020 (Pre SmartSystem). Performance Line CX 2021 SmartSystem is BDU3740.

Although some ebikes, like Cannondale Moterra Neo 3 do not use the Bosch Assembly Plates, and motor is assembled directly to the ebike frame.

 

[Bummers]

Yep, this is the info cube were incorrectly using apparently.

 

[Straker]

Hey guys, I have a carbon frame e-bike that's recently developed a creaking noise by the bottom bracket that comes with every pedal stroke.
I regreased and reinstalled the pedals, cranks and even the seat, nothing seemed to work. Extremely annoying.

My next step was the motor mount bolts, I couldn't find documentation on what the torque specs were beyond a 2 page document that stated "20nm" for another similar ebike model (both carbon and aluminum), so in a sweaty irritated rush I took the bolts out, regreased and reinstalled.

First major dummy move, I had my wrench set to 20ft/lbs instead of 20nm, a whopping 27nm of torque. Next dummy move, I realized that 20nm itself was probably overkill for a carbon frame, upon further research it seems like general consensus is 11nm, not 20nm!

I immediately backed off and retorqued to 11nm and left it, and fortunately I didn't hear any cracking or detect any damage on the frame itself, but now I'm paranoid I've done myself in. I've recently reached out to the manufacturer to get the proper specs (what I should have done first), but I was curious to see what the folks here thought.

Here's an image of one of my mounts, they all seem "okay" but I'm no carbon expert.

View attachment 144906

Feel free to absolutely roast me in the comments

??? You greased the bolts! Please check what the manufacturers specs say…… it should normally have ‘threadlocker’

 

[Stihldog]

Each time I remove a motor I clean and add blue lock tight to the mounting bolt’s threads . I then torque to spec, which is 20nm for my Rail 9.7 carbon frame.

The lock tight can act as a lubricant, (threads only) without the need for grease, and helps prevent loosening of these bolts. A small amount of grease in the bolt-pocket can help. If you ever hear a creak coming from this area…stop riding. Recheck the torque’s on the motor mount bolts and bracket screws.

 

[Stihldog]

??? You greased the bolts! Please check what the manufacturers specs say…… it should normally have ‘threadlocker’

I do apply grease to the left/right threads of a peddle. These are usually self tightening and directional so lock tight isn’t necessary.

 

[Spiff]

For pedals and suspension bolts, I apply anti-seize grease

ANTI SEIZE - BIKE LINE

MOTOREX ANTI SEIZE is a special mounting paste for metal and aluminium connections including any parts that need to be press-fit, aluminium supports in metal frames and all screw connections.

motorex.com

 

[Straker]

I do apply grease to the left/right threads of a peddle. These are usually self tightening and directional so lock tight isn’t necessary.

My comment was for the originator.

 

[Hattori-Hanzo]

Looking at mondraker it's far more beefy and better built!

It seems that's how cube gets the best price point for their bikes, cheap out with the Chinese carbon frames.

Do you have any pictures of the Mondraker mounts, I had a quick google but couldn't find anything.

Financially it would make sense for them to out source the frames, like many other manufactures do (Whyte's carbon frames are made in Taiwan) From what I can see all Cube bikes are assembled in Germany.
I've read that China has some of the most advanced carbon production facilities in the world, the frame will be made to Cubes specification, whether that specification is up to the task is the question rather than where it was made?

 

[Mikerb]

One of the reasons I would never buy a carbon frame MTB is well illustrated in those photos!! Carbon is strong when forces applied are in the intended direction of the layup used. That is invariably compression force. Where something needs to be fixed to a composite construction, significant additional reinforcement is required..........and like most aspects of composite construction that can only be done by hand. At the BB area of a bicycle frame, forces applied are not linear ( compression or stretch)..........they include force at 180 degrees.............that means reinforcement needs to be multiple layers of UD at different angles to form a matrix for example. Those photos are a disgraceful example of poor design in my opinion.

 

[DBSwiss]

Hey guys, I have a carbon frame e-bike that's recently developed a creaking noise by the bottom bracket that comes with every pedal stroke.
I regreased and reinstalled the pedals, cranks and even the seat, nothing seemed to work. Extremely annoying.

My next step was the motor mount bolts, I couldn't find documentation on what the torque specs were beyond a 2 page document that stated "20nm" for another similar ebike model (both carbon and aluminum), so in a sweaty irritated rush I took the bolts out, regreased and reinstalled.

First major dummy move, I had my wrench set to 20ft/lbs instead of 20nm, a whopping 27nm of torque. Next dummy move, I realized that 20nm itself was probably overkill for a carbon frame, upon further research it seems like general consensus is 11nm, not 20nm!

I immediately backed off and retorqued to 11nm and left it, and fortunately I didn't hear any cracking or detect any damage on the frame itself, but now I'm paranoid I've done myself in. I've recently reached out to the manufacturer to get the proper specs (what I should have done first), but I was curious to see what the folks here thought.

Here's an image of one of my mounts, they all seem "okay" but I'm no carbon expert.

View attachment 144906

Feel free to absolutely roast me in the comments

You can probably find a service manual for your exact bike by googling it or maybe somebody posted it on a forum already. It will have all the torque specs. The motor bolts on my bike (a trek fuel exe 9.8) are torqued to 50nm so 20 may be low actually. It’s also a carbon frame. If the motor has screws to adjust the width, make sure they are set correctly to the width of your specific frame . Good luck!

 

[E-MAD MALC]

Looking at mondraker it's far more beefy and better built!

It seems that's how cube gets the best price point for their bikes, cheap out with the Chinese carbon frames.

There bikes are designed and engineered in Germany
And the frames are built in there own manufacturing site in Asia

 

[Spiff]

There bikes are designed and engineered in Germany
And the frames are built in there own manufacturing site in Asia

Mondraker bikes are designed and engineered in Spain, Cube in Germany

 

[Bummers]

There bikes are designed and engineered in Germany
And the frames are built in there own manufacturing site in Asia

Either poor design/QC or cheap/inferior methods used. That tiny amount of material on a crucial structural part of the frame is a joke. Throw in incorrect torque values and then cube refusing warranty claims on the basis of 'wear and tear'!