Snapped carbon crank

[NSFRACING28]

Hi all, has anyone had any issues with breaking carbon cranks on their e-bikes? I have a new 2019 S-Works and within the first 20 mins of riding it, for the very first time, the end snapped off the end of the crank following a minor pedal strike. I was riding up a mild gradient that was winding and quite rocky. It was a relatively mild pedal strike on the end of the pedal, insignificant enough for me to not give it another thought. Unfortunately this meant that when I went for the next push down the pedal was no longer under foot and I went over the handle bars. More than a bit embarrassing! When I picked myself up and worked out what had happened, the guy that I was riding with (on a Giant e-bike) and just stood and looked at each other in shock. The end of the crank had snapped clean off as per the photos attached.
I pushed the bike back out of the forest and straight into the supplying Specialized dealer (who luckily are right outside the forest). They too were shocked and took photos of all the damage.
To cut a long story short, the cranks were sent back to Praxxis with the pedal and they say there was no manufacturing fault and it was due to the nature of the pedal strike. Both I, and the LBS believe that if that is the case, how can they be fit for purpose?

 

[All Mountain Coaching]

That's a pretty serious pedal strike though by the pedal.

I had 3x sets of Race Face next sl carbon cranks fail, and that wasn't even due to damage nor strikes. The next r faired much better, shame they didn't fit the Levo.

 

[R120]

Wonder if some crank boots would have helped - personally not a fan of carbon parts on an EMTB.

 

[Xeretic]

Jeez, that looks bad. I guess going metal on the cranks (and most other parts - like the frame) is justified for eMTB considering the additional weight and possibility of pedal strikes. Hope your LBS will get it fixed for you at reasonable terms.

 

[jerry]

I think hitting the outside of the pedal leverages the impact forces on the crank. It exerts its power on the mid of the crank instead on the crankshaft (perhaps, luckily so). I've had a Miranda Alu crank totally bent inwards, and it wasn't even the sort of impact that would deadstop my pedalling. You just hit it on the weakest possible point.

 

[Slowroller]

I've beaten the hell out of carbon cranks without issue, hundreds of direct rock stikes at least. You should see the pedals I used to ride lol. I used to be a test rider, so that was part of the gig, see what it takes to break stuff. That is definitely a defective part. Praxxis should have replaced them asap just to keep you from spreading those images.

 

[NSFRACING28]

That's a pretty serious pedal strike though by the pedal.

I had 3x sets of Race Face next sl carbon cranks fail, and that wasn't even due to damage nor strikes. The next r faired much better, shame they didn't fit the Levo.

That’s interesting that you think the pedal show a serious pedal strike? I think it shows that it was actually minor and glancing (which it was)?

 

[NSFRACING28]

I've beaten the hell out of carbon cranks without issue, hundreds of direct rock stikes at least. You should see the pedals I used to ride lol. I used to be a test rider, so that was part of the gig, see what it takes to break stuff. That is definitely a defective part. Praxxis should have replaced them asap just to keep you from spreading those images.

That was my thoughts, and that of the guys in the local bike shop.

 

[mtbbiker]

My Sram carbon cranks look like crap at the ends from strikes. I had a friend with the same Sram cranks, fairly new like yours and broke just like yours. Sram warranties it no questioned ask, and replacement cranks have been solid.

 

[deanphoto]

I snapped a carbon Praxis crank arm a few weeks back. Looks to be almost identical to yours.

 

[deanphoto]

I snapped a carbon Praxis crank arm a few weeks back. Looks to be almost identical to yours. View attachment 14830 View attachment 14831

For what it's worth mine were replaced under warranty without question. Apparently the first snapped Praxis that Specialized UK had seen.

 

[Pdoz]

Hmmm....dear mr praxis, can I please have my cranks back so I can have them independently tested , and then advertise the results of what you consider acceptable construction?

Oh, and dear specialized ....praxis thinks this is acceptable - do you?

How much do they spend on advertising?

 

[All Mountain Coaching]

That's a pretty serious pedal strike though by the pedal.

I had 3x sets of Race Face next sl carbon cranks fail, and that wasn't even due to damage nor strikes. The next r faired much better, shame they didn't fit the Levo.

That’s interesting that you think the pedal show a serious pedal strike? I think it shows that it was actually minor and glancing (which it was)?

I was only going on what my pedals look like. When I started Emtb I caught them more and they aren't that scarred.

 

[jwrx]

Damn i just ordered mine and its arriving this week. My manual bike has a set of sram XO1 carbon cranks that have withstood 4 years of crank bashing over horrendous rock gardens, and they look like crap...but still solid

 

[NSFRACING28]

For what it's worth mine were replaced under warranty without question. Apparently the first snapped Praxis that Specialized UK had seen.

They replaced mine, but with Praxis saying no manufacturing fault, there’s no way they are going back on my bike!

 

[NSFRACING28]

Hmmm....dear mr praxis, can I please have my cranks back so I can have them independently tested , and then advertise the results of what you consider acceptable construction?

Oh, and dear specialized ....praxis thinks this is acceptable - do you?

How much do they spend on advertising?

I didn’t get mine back either. To make matters worse, one of the fork CSUs was damaged in the crash. As they refused to cover the cost I decided to get the shop to replace it anyway. They ordered the correct E-bike specific part but when it arrived, it turns out that the forks fitted to my bike are not the E-bike version at all, they are the standard fork. It even has the E marking on the leg. The shop have had to send it back and get the standard CSU as the piston and valving won’t fit. I am waiting for a reply from Specialized regarding that one!

 

[Mikerb]

I snapped a carbon Praxis crank arm a few weeks back. Looks to be almost identical to yours. View attachment 14830 View attachment 14831

I would say that one has delaminated .....no way the carbon laminate should not be stuck to the foam core. I am surprised looking at the pics of broken cranks that no form of sandwich is used in the layup. Also the rectangular shape would normally be reinforced on the corners with a stronger laminate ......dont like the construction method at all!

 

[dirt huffer]

I've snapped a carbon crank arm. Split it down the middle. I just go with aluminum cranks now

 

[R120]

I think we an EMTB, there is absolutely nor reason to have a Carbon crank other than aesthetics - for me the strongest crank is going to be the one I want

 

[Brianjonesphoto]

Carbon is not a miracle material. I'm shocked every time I see carbon parts on a MTB let alone and EMTB. I choose duriblity over weight every day. Tends to be cheaper too. Total carbon parts on my Meta, 0

 

[All Mountain Coaching]

For what it's worth mine were replaced under warranty without question. Apparently the first snapped Praxis that Specialized UK had seen.

They replaced mine, but with Praxis saying no manufacturing fault, there’s no way they are going back on my bike!

Are you selling them?

 

[NSFRACING28]

Are you selling them?

No, I’ll give them away with the bike when/if I sell the bike.

 

[Gary]

I think we an EMTB, there is absolutely nor reason to have a Carbon crank other than aesthetics - for me the strongest crank is going to be the one I want

When i first got my Emtb. I wished shimano did a SAINT level Emtb crank.
Mainly as that's the crank I have on most of my regular bikes and I notice the difference in flex in any other Shimano crank. and mainly as they are among the few cranks I've never bent/broken
After going through multiple motor bearings I now would rather have the weaker E8000 cranks as it's more likely the crank will bend rather than transfer the load to the axle/bearings.
I'm not talking about pedal strikes BTW. i'm talking about big hits from jumps or drops, messed up landings, and big crashes where the bike smashes into stuff.
DH, Enduro and DJ bikes. I do want strength though.

Carbon is not a material I'd even consider for an mtb crank.

 

[SinCityJets]

Based just on this post, I am NEVER putting anything from Praxis on my bike.

 

[Lee Dove]

That's a pretty serious pedal strike though by the pedal.

I had 3x sets of Race Face next sl carbon cranks fail, and that wasn't even due to damage nor strikes. The next r faired much better, shame they didn't fit the Levo.

I got through 2 sets of next sl and have just had the pedal inserts on a pair of SIXC fails.

I hate Race Face stuff, only used it when it is original fit on a bike.

With the higher likelihood of pedal strikes on an ebike strong alloy cranks is the way to go. I see zero benefit of carbon cranks on an ebike.

 

[MarkH]

Wouldn't like to go 'gas to flat' on them. ??

 

[Mondfuchs]

Tata.... find the fault in the picture....

this was the kicker before it went broken - seems not that big

I was very lucky that I could smoothly break the bike and I didn't felt down. So I had a really good angel who supported me in this circumstances. I went immediately to my dealer and he replaced with Alu crank which I've asked.
I'm not going anymore to carbon on this crucial part of the bike as this could be extremely dangerous - I mean I made many other bigger jumps before and if this would happen then I would be potentially in other situation.

As I do have filmed this scene were the crank get broken I will send to Specialized and Praxiswork to get feedback - based on experiences here in the forum I could see the crank as construction/design issue.
Hands Off of this crank - probably hands off from Carbon Crank at all when you go Bikepark

 

[KeithR]

I'm not going anymore to carbon on this crucial part of the bike as this could be extremely dangerous

Now imagine it was your down tube or seat tube, rather than your crank arm.

This is what carbon fibre is known to do - completely unanticipated catastrophic failure - and it often takes very little to provoke it, because small, unnoticed impacts can seriously compromise the strength of carbon fibre without the damage being visible on examination of the component.

Honestly, "structural" carbon fibre on mountain bikes and ebikes scares me. I've been using equipment made from carbon fibre for 40+ years now - obviously not in a biking context - so I'm deeply familiar with its qualities and characteristics: I know how strong it is, but it isn't tough the way aluminium, steel, titanium are.

And metals bend before they fail.

I reckon the only part of a bike I'd be happy to be made of carbon fibre, is the bottle cage...

 

[Mikerb]

Now imagine it was your down tube or seat tube, rather than your crank arm.

This is what carbon fibre is known to do - completely unanticipated catastrophic failure - and it often takes very little to provoke it, because small, unnoticed impacts can seriously compromise the strength of carbon fibre without the damage being visible on examination of the component.

Honestly, carbon fibre on mountain bikes and ebikes scares me. I've been using equipment made from carbon fibre for 40+ years now - obviously not in a biking context - so I'm deeply familiar with its qualities and characteristics: I know how strong it is, but it isn't tough the way aluminium, steel, titanium are.

And metals bend before they fail.

I reckon the only part of a bike I'd be happy to be made of carbon fibre, is the bottle cage...

I agree. It would not be quite so bad if items were at least adequately described. Just specifying an item as constructed in Carbon telss you no more than describing an item as made of wood....which could be anything from chipboard to African Teak.

 

[Mcharza]

Tata.... find the fault in the picture....

View attachment 36669



this was the kicker before it went broken - seems not that big

View attachment 36670

I was very lucky that I could smoothly break the bike and I didn't felt down. So I had a really good angel who supported me in this circumstances. I went immediately to my dealer and he replaced with Alu crank which I've asked.
I'm not going anymore to carbon on this crucial part of the bike as this could be extremely dangerous - I mean I made many other bigger jumps before and if this would happen then I would be potentially in other situation.

As I do have filmed this scene were the crank get broken I will send to Specialized and Praxiswork to get feedback - based on experiences here in the forum I could see the crank as construction/design issue.
Hands Off of this crank - probably hands off from Carbon Crank at all when you go Bikepark

View attachment 36671
View attachment 36672

for the first pic. Glad you managed the landing. Those Praxis carbon cranks are piece of s..it for park riding