Front sprocket detached from crankset - Why? Has it happened to anyone else?

[M. Tartiflette]

I went out on a ride yesterday only for the front socket to detach from the crankset. Sod's law meant it happened the furthest distance from our house and I was forced to walk uphill and coast downhill over the 7 kms back.

Prior to this there was little warning. Yes, there was sometimes skipping when changing gears and some chain noise in some gears (but not others). But it didn't seem a major issue and I figured it could be addressed when I took it in for a service next week.

Any Forum wisdom would be much appreciated. Is this a common problem? What could be likely causes?

Some background info - the bike's a Cube Touring Hybrid Pro. 1 year old - ca. 2,000 kms on the clock. I have washed and lubricated the chain every 2-300 kms. According to my gauge the chain is still okay.

 

[soundwave]

ebikes can take a hammering vibration wise so every bolt on my bike now has lock tight on them and a couple of cable ties just in case.

1 pivot bolt for my bike is £30 on its own so dont want to loose any more.

my front sprocket lock ring can also come loose so make sure to check it now and then to make sure it is still tight.

 

[Andy-Mat]

I went out on a ride yesterday only for the front socket to detach from the crankset. Sod's law meant it happened the furthest distance from our house and I was forced to walk uphill and coast downhill over the 7 kms back.

Prior to this there was little warning. Yes, there was sometimes skipping when changing gears and some chain noise in some gears (but not others). But it didn't seem a major issue and I figured it could be addressed when I took it in for a service next week.

Any Forum wisdom would be much appreciated. Is this a common problem? What could be likely causes?

Some background info - the bike's a Cube Touring Hybrid Pro. 1 year old - ca. 2,000 kms on the clock. I have washed and lubricated the chain every 2-300 kms. According to my gauge the chain is still okay.

Guessing only, you have a middle motor bike, where ALL the motor power AND the "leg" power, go through the same piece of chain.
Most bike chains were never designed to handle this type of strain, long term.
2000 KMs is long term. Change the chain at least wach 1000 KMs, and replace the rear cassette, every second year at around 2000 KMs.
But do remember that the distances are mention are for some serious hills, flat areas will take longer to wear out the various parts....
It is probably the single worst and weakest point with regard to middle motor bikes. It put me off from day one, even before I bought my first e-bike, so I have not ever bought one.
Also, middle motors not only have some weak points, and some of the manufacturers are a further weak pont, but they are usually far more expensive!
I cannot think of one single positive reason to buy such a bike....
I can only recommend, in the long term, a bike with either a rear (my favorite) or front hub, as they will get you home with the chain removed.
Mid motors won't...
Been there, done that and got the T-Shirt! (I mean that I have ridden home, up hill and down dale without a chain, on a rear hub motored e-bike.)
Mechanically, mid motor bikes are designed for countries like Holland, with basically no hills, far less chain drive stress...!
Andy

 

[Gringo]

“Mechanically, mid motor bikes are designed for countries like Holland, with basically no hills”
seriously, I think a lot of people here would disagree, along with all the e-mtb manufacturer's

 

[Hyp4r]

Guessing only, you have a middle motor bike, where ALL the motor power AND the "leg" power, go through the same piece of chain.
Most bike chains were never designed to handle this type of strain, long term.
2000 KMs is long term. Change the chain at least wach 1000 KMs, and replace the rear cassette, every second year at around 2000 KMs.
But do remember that the distances are mention are for some serious hills, flat areas will take longer to wear out the various parts....
It is probably the single worst and weakest point with regard to middle motor bikes. It put me off from day one, even before I bought my first e-bike, so I have not ever bought one.
Also, middle motors not only have some weak points, and some of the manufacturers are a further weak pont, but they are usually far more expensive!
I cannot think of one single positive reason to buy such a bike....
I can only recommend, in the long term, a bike with either a rear (my favorite) or front hub, as they will get you home with the chain removed.
Mid motors won't...
Been there, done that and got the T-Shirt! (I mean that I have ridden home, up hill and down dale without a chain, on a rear hub motored e-bike.)
Mechanically, mid motor bikes are designed for countries like Holland, with basically no hills, far less chain drive stress...!
Andy

You for real????

 

[Andy-Mat]

“Mechanically, mid motor bikes are designed for countries like Holland, with basically no hills”
seriously, I think a lot of people here would disagree, along with all the e-mtb manufacturer's

Of course they would disagree, but the customers that eventually get problems, all regret being conned. But would never actually stand up and say it!
These mid motor bikes would last FAR longer in Holland, as I implied, or any similar flat area, even in the UK, but having all the available power going through a chain, theysame size as on many normal bikes, stresses that part dramatically, and the gears it drives.
Wearing out the associated parts, and as I said before, causing many owners to have a walk home when, not if, it breaks!
Many, but certainly not all, e-bike riders know this, and some carry a chain and the required tools with them on all rides, simply for that reason!!!
It still surprises me that people still buy mid motor bikes, even the ones who KNOW all the possible problems with them! But of course its a personal choice, as none of us live in North Korea under a dictator!!!
Andy

 

[soundwave]

Of course they would disagree, but the customers that eventually get problems, all regret being conned. But would never actually stand up and say it!
These mid motor bikes would last FAR longer in Holland, as I implied, or any similar flat area, even in the UK, but having all the available power going through a chain, theysame size as on many normal bikes, stresses that part dramatically, and the gears it drives.
Wearing out the associated parts, and as I said before, causing many owners to have a walk home when, not if, it breaks!
Many, but certainly not all, e-bike riders know this, and some carry a chain and the required tools with them on all rides, simply for that reason!!!
It still surprises me that people still buy mid motor bikes, even the ones who KNOW all the possible problems with them! But of course its a personal choice, as none of us live in North Korea under a dictator!!!
Andy

5 years old and always had a dongle fitted done 7000 miles and like new inside, i even sold my old 11spd cassette as plenty of life left in it as went 12spd.

chains wear out on any bike but i have had about 5 in that time and only one snapped because i changed a part on the rear mech and it failed and took out a chain with it.

and it has been up plenty of hills and can go 30mph +

 

[Andy-Mat]

View attachment 35311View attachment 35312

5 years old and always had a dongle fitted done 7000 miles and like new inside, i even sold my old 11spd cassette as plenty of life left in it as went 12spd.

chains wear out on any bike but i have had about 5 in that time and only one snapped because i changed a part on the rear mech and it failed and took out a chain with it.

and it has been up plenty of hills and can go 30mph +

There are exceptions to any rule.
You may find this article informative, I did!

Electric bicycle hub motors vs mid-drive motors: Which should be on your next e-bike?

Electric bicycles are becoming increasingly popular forms of two-wheeled electric transportation for both commuting and pleasure riding. The two most...

electrek.co

Electric bicycles are becoming increasingly popular forms of two-wheeled electric transportation for both commuting and pleasure riding. The two most common electric motor styles used in today’s electric bicycles are hub motors and mid-drive motors. Which one is best for your needs? Read on to learn more and find out!

Hub motors, which place the electric motor in the center of a bicycle wheel, are certainly the most common form of electric bicycle motors.

Mid-drive motors, which house the motor closer to the center of the bicycle and transfer the motor’s power to the rear wheel via the bicycle’s chain drive, have become much more common over the last 2-3 years, and are cutting significantly into the hub motor’s lead as the king of the e-bike motors.

Both have a number of unique advantages and disadvantages, so choosing the right motor for you will largely depend on your requirements and which advantages seem more useful to your needs.

Electric bicycle hub motor advantages

One of the biggest advantages of hub motors is that they require little or no maintenance. They are an entirely independent drive system that retain all of their components inside the motor casing, leaving nothing for you to mess with or maintain.

That enclosed system also means there is a lot less to fail. There are two types of hub motors: geared hub motors which have internal planetary gears to reduce the speed of a higher RPM motor, and gearless hub motors, which have no gearing and directly connect the lower RPM motor stator’s axle to the bike. Geared hub motors usually have just one point of weakness: the gears. Over time, a tooth can break off and the reinforced nylon gears will eventually strip.

Gearless hub motors, on the other hand, have zero moving parts aside from their bearings, so there is basically nothing to wear out. As long as they don’t rust out or wear down their bearings, they can pretty much last forever.

Hub motors also help reduce other bike maintenance tasks compared to mid-drive motors. Since they don’t connect to the main pedal drive system, hub motors don’t add any extra stress to your chain or shifters, and don’t cause any of those parts to wear out more quickly. If anything, your chain will probably last longer than a non-electric bike because the hub motor will be doing more work, allowing your chain to often sit idle.

As an independent drive system, hub motors also add redundancy. Since the hub motor and the pedal drive system are completely independent, you can lose one and still get home on the other. Chain breaks while you’re hitting it hard on a trail? Toss the chain in your bag and ride home on just electric power. Hub motor somehow fails? Pedal back. Either way, you’ve got a backup. This can be huge if you’re far from home, especially for older riders or those who use e-biking as a form of rehabilitation.

The weight of a hub motor can both positively and negatively affect the balance of a bike, depending on the circumstances. In some cases, it can be nice to have the weight of a motor farther forward or backward in one of the wheels. This is especially true of e-bikes with rear mounted batteries. In such cases, a front hub motor can redistribute the weight so the center of gravity is still in the center of the bike.

Lastly, hub motors are much cheaper than mid-drives. Hub motor bikes are mass-produced by the hundreds of thousands, perhaps even millions depending on the factory. The same designs have been in constant use for over a decade in some cases. This means that the prices are astoundingly cheap.

As we’ve covered in some of our past DIY e-bike articles, you can get an entire 1,000 W hub motor kit, including the electronics, throttle, etc, for under $200. The same power level in a mid-drive kit can easily cost 3-4x as much.

For the complete article, please read the web link.

Other interesting articles can be found here:-

Electric Bike Motor Comparison: Hub, Mid Drive, & Friction Drive

Here is a comparison of the different electric bike motor systems to help you determine which configuration is best for your riding needs. In this article there are the pros and cons of each system: the hub motors (front and rear), the mid drive motor, the friction drive motor, and the rocket...

electricbikereport.com

This was particularly interesting for me personally, and fully supports my reasoning (surprise, surprise!):-

Electric bicycle - Wikipedia

en.wikipedia.org

Another type of electric assist motor, often referred to as the mid-drive system, is increasing in popularity. With this system, the electric motor is not built into the wheel but is usually mounted near (often under) the bottom bracket shell. In more typical configurations, a cog or wheel on the motor drives a belt or chain that engages with a pulley or sprocket fixed to one of the arms of the bicycle's crankset. Thus the propulsion is provided at the pedals rather than at the wheel, being eventually applied to the wheel via the bicycle's standard drive train.
Because the power is applied through the chain and sprocket, power is typically limited to around 250–500 watts to protect against fast wear on the drivetrain.

regards
Andy

 

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Swindon Powertrain | Manufacturing | Testing | Design

Swindon Powertrain is led by a team of innovative, highly experienced engineers who develop and manufacture high-tech powertrain solutions.

swind.life

if that was 5 grand id buy one 15kw

 

[Gringo]

as I said before, causing many owners to have a walk home when, not if, it breaks!

Andy

Anybody here had to walk home through a drive train failure. ?

Personally in nearly 50 years of cycling I’ve only had one chain brake and that was on a non E mtb. I’ve had no problems with the 3 E-mtb’s I’ve owned.

 

[Gaz]

Personally in nearly 50 years of cycling I’ve only had one chain brake and that was on a non E mtb.

Over 50 years (just) on two wheels and never had a chain break. In my youth, chains would only get the occasional bit oil if they were seizing up - oil was a far more important commodity for my skateboard wheels

Gaz

 

[mike killay]

My mid drive Tonaro motor lasted 7 years before an internal clutch broke. I was able to buy a complete motor and gear box assembly from China for £289. This included Chinese export tax, UK Customs duty and the courier.
All that I to do was unbolt the old motor/gear box, remove the cranks and transfer them and then bolt all together again. Took about half an hour including the wiring.
Granted, possibly not as ultimately reliable as a hub motor, but so much more torque for hills.

 

[Andy-Mat]

Anybody here had to walk home through a drive train failure. ?

Personally in nearly 50 years of cycling I’ve only had one chain brake and that was on a non E mtb. I’ve had no problems with the 3 E-mtb’s I’ve owned.

Then consider yourself very lucky.
Nobody, especially not me, is saying that it happens to all owners of mid motor bikes, but they do stress the drive train/chain, more than any other e-bike system.
Its also patently obvious for anyone who has at some point, trained and worked as an engineer, but not so obvious to anyone NOT so trained.
Furthermore, the links I provided all maintained the same single point of concentrated stress, but you may have not read all that I posted, so you would not even know that!
Have a great day you lucky person you!
Andy

 

[Andy-Mat]

My mid drive Tonaro motor lasted 7 years before an internal clutch broke. I was able to buy a complete motor and gear box assembly from China for £289. This included Chinese export tax, UK Customs duty and the courier.
All that I to do was unbolt the old motor/gear box, remove the cranks and transfer them and then bolt all together again. Took about half an hour including the wiring.
Granted, possibly not as ultimately reliable as a hub motor, but so much more torque for hills.

If you accept that as normal, please do, your personal choice.
But hub systems, especially those without a gear box, are so reliable that in almost 10 years of e-biking, I have still not had the need to open up a motor! And that, according to the links I posted, is NORMAL for hub motors.
Furthermore, hub motors are simple, the only vaguely electronic components they have are Hall effect sensors in the BLDC motors, which are very easily repaired by anyone who can undo a few nuts and screws, and solder reasonably well.....there are even good videos on youtube showing how its done!
Hub motors are definitely very simple, and even if the guarantee has run out, no requirement to send them to the manufacture to get repaired as Bosch requires......at mind numbing prices....with spares not even allowed to be carried by the bike shops that sell the bikes new!
Andy

 

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at the end of the day a chain is a wear part and should be checked as it will wear out but it really does depend on what conditions you ride in and what you do to look after it and keep it clean and lubed.

keeping the gears indexed right esp on my 12spd and 11spd drive train was key to making it last as not much given the distance of the rear mech travel and half a turn on the shiftier cable adjust can screw it up shifting wise in some gears and doing it going 30mph well it makes a bang even with a xx1 12spd mech as it has to be spot on indexing wise with the b screw adjustment and even have a tool just for that and must be set with 20% sag on the rear sus.

 

[Darren Hayward]

I've had a front hub and a mid drive. The mid drive out performs the Hub drive in every respect. Did the hub drives ability to get me home without a chain give me a warm feeling? No. Pushing the bike up hills (cause the motor on its own won't do it) did not appeal to me so I carried a chain tool and missing link. The same tools I carry now. If someone really doesn't like carrying tools then I wish them good luck with their first puncture.


Darren

 

[Darren Hayward]

Oh, by the way. The original post wasn't about chains.

 

[georgehenry]

I have two rear hub drive bikes and a Yamaha crank drive hard tail Haibike and love them all.

But for proper off road riding the crank drive is far superior with better weight distribution and climbs like a mountain goat. They really come into their own on steep technical single tracks. Built for the flat they are not.

My Yamaha Haibike cost £1750 in March 2015, has just passed 12,000 miles, and still uses it original 400Wh battery now entering its 6th year.

Andy you have strongly held opinions on a couple of pet topics, how to look after a battery being one, and a less than flattering opinion of Bosch being another, and of course your preference for a hub drive bike, but as Bertram Russel said "If you are certain, you are certainly wrong".

I think you are right that hub drive bikes are a bit overlooked now, and for commuting on the road and general errands and shopping a hub drive is my preference.

And yes, crank drive bikes do wear their drive trains much more than hub drives.

 

[Andy-Mat]

I've had a front hub and a mid drive. The mid drive out performs the Hub drive in every respect. Did the hub drives ability to get me home without a chain give me a warm feeling? No. Pushing the bike up hills (cause the motor on its own won't do it) did not appeal to me so I carried a chain tool and missing link. The same tools I carry now. If someone really doesn't like carrying tools then I wish them good luck with their first puncture.


Darren

The impression I am getting from you is that you are comparing an apparently poor front hub bike (not my personal choice either after trying one out many years ago), against a better (far more expensive probably if new?) Mid motor bike?
Which is partly the reason I went for rear hub twice, and have been most happy with, even though the second bike new was at the time, and one of the cheapest on the market then.
The many Bosch bikes here I have had a ride on were great when running correctly, I liked them at first!
But since I had my first rear hub, around 9 years ago now, and not having any problems that I could not fix mainly adjustments and a few worn parts over the time, and one chain link that slipped off and got lost (the bike was secondhand when I bought it!), and seeing what friends and acquaintances with Bosch bikes were experiencing, (Germans always buy the most expensive articles, as its a way of showing off!), but mainly due to the unfair business practices and broken gears and such stuff, plus the exorbitant prices charged for everything here, not forgtétting the time it took to get stuff fixed (none are DIYers!), totally put me off.
It put several of them off as well!
The only Bafang "friend" I know, appears to ride a lot (last year), and he was plagued with wear on the chain (here are hills that most UK people might call mountains!), but I have no actual information as to the total distances he covered, and he has since sold the bike last year, and bought a rear hub, that looks also quite expensive, though I have not noted the name/type, and since 2019 (last winter and COVID-19 probably), I have not seen him at all since around November probably...I hope that he is OK.
But what ever you prefer, it does appear that where, how far, how often and how you ride, especially with certain mid motor versions, does seriously affect the life expectancy of the bike's motor and drive.
This is also noted accurately (IMO), in all of the links I recently posted on the subject, as it is apparently well understood in the industry at least!
Perhaps some people, guessing only, are simply replacing their bikes, once the guarantee has run out, or when problems arise, just as many do with their cars, could possibly be an answer for some...
I wish you a great day.
Andy

 

[MikeS]

Andy - many people on here, like me, may have had the very limited experience of one hub motor and one crank motor - in the Carrera bikes from Halfords. Admittedly the hub implementation on the Carrera Crossfire must have been faulty from a design or spec point of view as many many owners have had problems. Whereas the Bosch implementation of the mid-drive on the Carrera Crossfuse, seems almost trouble free.
Anyway back to the original post - I thought when I first read it that you must have a Carrera Crossfuse, because I discovered after a few hundred miles on mine that all the bolts that held the front sprocket were backing out. Halfords stripped it and applied loctite which must have been missed at the factory, and I understand that at least my local Halfords store routinely loctites them now on assembly.
Mike