eMTB pedal crank falling off

[pgrbff]

I know there are some bike users on here, not me though.
The crank on one side of my son's e Haibike fell off this morning. I took everything apart, cleaned it all well and reassembled it. I didn't have an 8mm hex to put on the torque wrench, I'm not used to bikes but by car standards, 55N is not a lot. the outer 10mm was done up to the required 15N.
It fell off again. The inner bolt had come undone and it is covered in aluminium dust.
I think at some stage it must have come off and he just quickly did it up again, the teeth on the crank are a bit mangled at the ends, but it felt solid enough when I put it back together.
Any ideas? I have no idea about bikes.

 

[clogs]

for nuts n bolts that have a habit of coming loose use a little Blue locktite/ Screw Lock....there are stronger types but not in this case.....cheap....
in design said nuts n bolts are rarely a problem now esp as Left Hand threaded gear/Nylock nuts etc etc are redily available....
I suspect there are other problems going on with ur bike....

 

[pgrbff]

the upper nut is covered in fine Aluminium dust/shavings

 

[pgrbff]

Apparently you are supposed to gease them but I did use some loctite. Still came undone very quickly.

 

[MikeJhn]

You said above "the teeth on the crank" is this a Shimano high end crank set, if so the crank has to be aligned with the splines on the bottom bracket, not as simple as the old square drive, put the crank on and turn it one way and the other until you feel the crank and bottom bracket have aligned, it will then push on further, you can feel it happen, only after this alignment is successful do up the bolt, I had this on a number of club cyclists cranks, mostly old boys who had not kept up with modern gear.

 

[pgrbff]

for nuts n bolts that have a habit of coming loose use a little Blue locktite/ Screw Lock....there are stronger types but not in this case.....cheap....
in design said nuts n bolts are rarely a problem now esp as Left Hand threaded gear/Nylock nuts etc etc are redily available....
I suspect there are other problems going on with ur

You said above "the teeth on the crank" is this a Shimano high end crank set, if so the crank has to be aligned with the splines on the bottom bracket, not as simple as the old square drive, put the crank on and turn it one way and the other until you feel the crank and bottom bracket have aligned, it will then push on further, you can feel it happen, only after this alignment is successful do up the bolt, I had this on a number of club cyclists cranks, mostly old boys who had not kept up with modern gear.View attachment 154940

From what I can determine as the inner bolt comes undone, and I've spent the last hour+ searching forums, the crank slowly works its way off and as it reaches the end of the aluminium splines they start to disintegrate.
Haibike customer service appears non-existent, they want you to go back to the shop every time you have a question, but the shop is 2 hours+ away and I spend hours researching the right bits online.
It would seem that once the crank starts coming off the only solution is to buy new ones, which is proving difficult as there are so many.

 

[sneggysteve]

Here's a good site for e bike help

https://www.pedelecs.co.uk/forum/categories/electric-bikes.1/

 

[Fergie 307]

From what I can determine as the inner bolt comes undone, and I've spent the last hour+ searching forums, the crank slowly works its way off and as it reaches the end of the aluminium splines they start to disintegrate.
Haibike customer service appears non-existent, they want you to go back to the shop every time you have a question, but the shop is 2 hours+ away and I spend hours researching the right bits online.
It would seem that once the crank starts coming off the only solution is to buy new ones, which is proving difficult as there are so many.

Once the splines have worn they will continually work loose, and yes the only solution is likely to be a new crank.

 

[MikeJhn]

This may help you to identify which crankset you have: https://si.shimano.com/en/pdfs/dm/MAFC002/DM-MAFC002-10-ENG.pdf these are all new too me as I only have Dura-Ace or Ultegra gear on my bikes.

And this:

 

[Homeless Squirrel]

You said above "the teeth on the crank" is this a Shimano high end crank set, if so the crank has to be aligned with the splines on the bottom bracket, not as simple as the old square drive, put the crank on and turn it one way and the other until you feel the crank and bottom bracket have aligned, it will then push on further, you can feel it happen, only after this alignment is successful do up the bolt, I had this on a number of club cyclists cranks, mostly old boys who had not kept up with modern gear.View attachment 154940

Good ole hollow tech! Think that's length i could do with? Have a boxed 116mm in my hand now oddly.

 

[Homeless Squirrel]

This may help you to identify which crankset you have: https://si.shimano.com/en/pdfs/dm/MAFC002/DM-MAFC002-10-ENG.pdf these are all new too me as I only have Dura-Ace or Ultegra gear on my bikes.

And this:

View attachment 155055

Unless SCRAM or other mickey mouse makes!

 

[Homeless Squirrel]

From what I can determine as the inner bolt comes undone, and I've spent the last hour+ searching forums, the crank slowly works its way off and as it reaches the end of the aluminium splines they start to disintegrate.
Haibike customer service appears non-existent, they want you to go back to the shop every time you have a question, but the shop is 2 hours+ away and I spend hours researching the right bits online.
It would seem that once the crank starts coming off the only solution is to buy new ones, which is proving difficult as there are so many.

Post some pics up of ends of bottom bracket shaft and crank arm guess it's non drive side?
Some of the late Shimano designs have an auto go home early feature where arm becomes detached! Think was Hollow tech two? or could be a later version! But not had my mitts on them for a long time.
Ive the older Shimano Dura Ace and Campagnolo but worked on many others as built/repaired bikes as used to run Eastway Cycle circuit before it got chewed up in to the Olympic Velodrome.

Once chewed up it's a replacement crank as the outer threads hold that other outer part which the inner bolt pushes against as done up.

Two things you need are the correct type to fit on shaft and the length 170.172.5.175 most just stick 175 on no matter what which for so many is too long.
Should be the standard/normal pedal thread size? BMX/Elcheapo cycles use the smaller pedal spindle threads.

Anything like this fastening? Race Face E-Bike MTB Crank | Chain Reaction

 

[pgrbff]

I think I have found one that will fit. Hours of searching, not the same model and 5mm longer but should work. I did get the old one to stay on for 50 or so km but came off in the end.