How to fix? (snapped crank bolt)

[gmurad]

Hey guys,

I snapped the crank arm bolt on my less than 2 weeks old 2020 Levo
I opened the motor to check it after the first ride which was very muddy and also took the time to reinforce the power cable.

After closing the motor I used my car tire torque wrench set to 49.5 Nm on the crank bolt. I was applying hulk level strength with a long leverage, no wonder it snapped. I guess my torque wrench is defective because it never clicked ... I thought I wasn't at 50Nm yet. Removing it also required hulk level strength

Now the bolt is spinning freely both ways, not sure what to do, attached a video a picture here:


Anyone has ideas? I don't have much experience with bikes, not sure what's happening here.

 

[ridesantacruz]

I am thinking since you snapped the bolt, you should be able to pull off the crank to see what's going on behind it. Then use a screw extractor to remove the remaining bolt. It will not come out easily because the bolt has loctite material on it. Hope that helps!

 

[gmurad]

Thanks for the reply, the crank doesn't seem to come out. Seems like it's very secure in there. I wonder if just the head of the bolt snapped but more of it is still threaded.

There is a retaining ring there as well, I wonder what function it provides.

 

[ridesantacruz]

I have taken the cranks off before, they feel like they are a tapered fit. I would try putting a puller such as a battery or steer wheel puller on the crank to see if it will come off. Then if the bolt is hollow, you can use a screw extractor. If not, then drill into the bolt and then use the screw extractor. There is no retaining clip and if there was additional threads, the bolt would not spin, it would either thread in or out depending you spinning in or out.

 

[EMTBehave]

I'm not even slightly a prude, but reading language like this in a subject line at the top of the forum really lowers the tone of the place. It's not needed.

 

[gmurad]

I'm not even slightly a prude, but reading language like this in a subject line at the top of the forum really lowers the tone of the place. It's not needed.

Sorry if it offends you, the broken English and language was meant as a joke. I'm actually pretty upset about the bolt. If a moderator finds it offensive they may change it.

Did you have something related to the topic to contribute or did you come here just to declare your higher morals? Maybe that's what is not needed?

 

[EMTBehave]

Sorry if it offends you, the broken English and language was meant as a joke. I'm actually pretty upset. If a moderator finds it offensive they may change it.

Did you have something related to the topic to contribute or did you come here just to declare your higher morals? Maybe that's what is not needed?

I came here to say what I said with no intention to "offend" you (do you actually have any right or reason to be offended by my comment?). If you don't like that I am sorry but anyway... I hope you get your problem fixed and are back on the bike as soon as possible.

 

[gmurad]

I was able to get some purchase on the threaded part of the screw by applying a lot of pressure through the top of the screw (the part that was spinning freely) and that allowed me to unscrew the entire bolt. Now I just need to find a replacement bolt for this.

 

[gmurad]

I think I found it: M24 BOLT/EXTRACTOR - Praxis Works

 

[JimBo]

I bet a bike shop will have that bolt

 

[steve_sordy]

You should not need "hulk level strength" on any part of your bike. The highest level of torque I have seen on any bike of mine is 40Nm, on the bottom bracket. Something that tight just feels completely wrong, so I tighten the BB until it feels right, using the specified tools. I used to keep my eye on it for a few weeks, but now I don't bother because I trust my own senses. Not gone wrong yet.

But I always use a torque wrench whenever carbon fibre is involved, I just don't feel correctly calibrated for that material.

 

[Webike]

I was able to get some purchase on the threaded part of the screw by applying a lot of pressure through the top of the screw (the part that was spinning freely) and that allowed me to unscrew the entire bolt. Now I just need to find a replacement bolt for this.

Good job on getting it out and it looks like you found the right replacement bolt.

 

[gmurad]

Praxis USA doesn't ship to Canada and their Canadian distributor doesn't have the bolt! Today I went to a few bike stores in the area and none of them have a spare one (it's a proprietary bolt to praxis). The store were I bought the Levo will try to get it from Specialized directly. I think I will be off the bike for a while. I'm in the biggest city in Canada but we are still not well served for e-mtb related things here (like it is in the UK and other parts of Europe).

I wouldn't want to ride in this weather anyways:

Does anyone happen to have a spare bolt or a spare/broken crank and is willing to sell the bolt from it? It's the Praxis M24 crank bolt. Thanks.

 

[Gary]

and...

Thread title of the year award goes to...

 

[Levo-Lon]

Is it just easier to buy the crank as it will have the bolt fitted or get a new crankset, as per shorter crankset thread.
Im not patient enough to wait for a bolt from wherever..

As said above, nothing on your bike will ever be car wheel nut tight.

 

[steve_sordy]

@gmurad
Is the bolt material suitable to be used in temperatures like that?
Have you heard of low temperature enbrittlement?

Where is a metallurgist when you need one?

 

[Benson]

@OP, where did you read it needed to go to 50nm???

 

[Simoto123]

As a qualified materials expert I can confidently confirm he snapped it.

 

[gmurad]

@gmurad
Is the bolt material suitable to be used in temperatures like that?
Have you heard of low temperature enbrittlement?

Where is a metallurgist when you need one?

@OP, where did you read it needed to go to 50nm???

The idea of the cold making the material brittle make sense, but I think in this case my torque wrench is just not working anymore, I hadn't used in a while. It's a large one so it provides a lot of leverage.

50Nm is marked on the bolt itself and it's also in the specialized documentation but in hindsight I must have applied a lot more than 50Nm.

 

[salko]

Yes, the crank bolt says 50Nm, I have also tightened this bolt to 50Nm not so long ago and while doing it I was not sure if my torque wrench is ok cause it went pretty hard with no click, but then finally clicked.
Interesting thing I came across now are this instructions for replacing the power cable, which at the last step tell you to tighten crank bolt to 40Nm. I guess this instructions were released about a month ago (when new revision of the cable was released) and maybe Specialized also revised this torque for crank bolt which now seems to be at more reasonable 40Nm ...

 

[gmurad]

Nice find @salko

 

[gmurad]

I like your version of the story, but the last step also says 6mm hex key while it's actually 8mm. So I'm more inclined to think this is a typo.

 

[salko]

Let's just believe only a '6 hex key' is a typo

 

[RickBullotta]

You should not need "hulk level strength" on any part of your bike. The highest level of torque I have seen on any bike of mine is 40Nm, on the bottom bracket. Something that tight just feels completely wrong, so I tighten the BB until it feels right, using the specified tools. I used to keep my eye on it for a few weeks, but now I don't bother because I trust my own senses. Not gone wrong yet.

But I always use a torque wrench whenever carbon fibre is involved, I just don't feel correctly calibrated for that material.

"Back in the day" the actual torque spec for many crank bolts was "limit of strength". I sh*t you not.

 

[Gary]

"Back in the day" the actual torque spec for many crank bolts was "limit of strength". I sh*t you not.

It was actually 70NM.

"Back in the day cranks" still exist on absolutely tons of cheaper bikes
if you go above it to say 80NM you risk deforming the crank taper.
If 70NM is your personal "limit of strength" fair enough

 

[Kaelidoz]

He low-keyed told you that you are weak haha.

Classic Gary.

 

[RickBullotta]

It was actually 70NM.

"Back in the day cranks" still exist on absolutely tons of cheaper bikes
if you go above it to say 80NM you risk deforming the crank taper.
If 70NM is your personal "limit of strength" fair enough

Ha ha. Anytime you wanna come ride we can test “limits of strength” and “capacity for beer”..?️‍???

 

[wepn]

the broken English and language was meant as a joke

Personally I think it's innovative use of the English language & not only perfectly acceptable but totally awesome. At first I thought it was authentic French Canadian franglais.

 

[gmurad]

Personally I think it's innovative use of the English language & not only perfectly acceptable but totally awesome. At first I thought it was authentic French Canadian franglais.

I'm glad someone gets the humour. Coming from traditional MTB groups where this would have been funny I think I miscalculated the audience in this forum.

The negative reaction to my title is likely representative of the demographics that is attracted to e-mtb (at least for now while prices are so high) which seems to be predominantly older males from developed countries (e.g.: England).

 

[JimBo]

We resemble that remark ?