[Closed] Carbon MTB Cranks, how many of you have broken them?

Probably not quite the way you are thinking but on some SRAM XO's the metal pedal threaded insert disintegrated on my first ride....

Not managed to break any of our XOs yet

On my third set of Next SL's, loose pedal inserts on the first two. If I break this set I'll be asking for something else.

X0 fine on mine.

I used XO1 cranks for two years with no issues including Enduro races and multiple trips to the Alps etc.

I am no lightweight either.

Have a set of old Next SLs in which I’ve had to re-glue the pedal inserts. Also have some XOs with loose inserts which I bought like that and tried to glue, not so successfully.

My sixc have stood up to being ****ted off with idle surprisingly well. Look more scuffed up than an alu crank would have though.

Broke an X01 crank last weekend, I’m back on aluminium cranks now. After breaking two carbon bars in the last few months as well I have had enough of the stuff!

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Can people who've broken stuff post up:

1) The break situation (ie in a crash, or JRA)
2) Their weight
3) The age of the part that broke

I've had Carbon cranks on all my bikes for years, done XC racing to DH racing and never broken anything (except myself.....) But i am a <70kg racing snake of a man 😉

thanks all. seems like pedal inserts are the main concern.

Ran X01 DH ones for several years, no issues. Have Sixc on the current bike, broke them JRA on their second ride, must have been faulty out of the box. Replacements going strong over a year of proper abuse later

Next SL's 2x pedal inserts went within 3 months. Replaced under warranty, and sold on the third pair. Got some XO's now, and these are doing sound. Both SL breaks were pedal insert failure's; one went climbing the other after snap, crackle and pop at cyb. 66kg, wheels on the ground rider, but I am primarily a roadie so my legs have awesome power 8)

Used Next and Sixc with no issues. Currently on XO, and apart from a few chips out of the surface, they have held up fine after 18 months

No issues with my 4 pairs (3x XX1 1x Next SL)

XO1 I battered for 2 years - back on XTR these days as the interface for SRAM annoyed me.

Seen more than a fair share of snapped Next SL cranks to put me off carbon for a lifetime.

The pedal thread insert bit in my Truvativ Noir cranks came loose at Hit The North earlier this year, like stompweavers pic but not quite so dramatic. They were about six years old but hadn't been thrashed by any means. I weigh about 70kgs and I'm not exactly a torque powerhouse, so that was a bit disappointing.

x01 broken for me too, small drop, 2 rides old.

I broke 2 Next SLs but that doesn't really count, it's not because they're carbon, it's because they're absolute shit.

And wore almost all the way through some ancient Noirs, they looked like a polished root, but they did grand

On second set of Sixc. In my riding group we currently have 3 set sbroken next and 2 broken Sixc

I would buy again!

Carbon makes no sense in cranks.

Carbon makes no sense in cranks

Loada nonsense, most if not all bike parts have a quantity of failure due to many factors.

TBH I think the problem is that as soon as you're making a carbon crank you're tempted to shave the grams. The failures mostly aren't about carbon, they're about design or they're about weakness at key locations

(having said that I'm back on my ancient XTR M970s, they're about the same weight as a sixc and seem impervious to all harm, even if they do look like they've been chewed by an iron puppy)

Kinda hit nail on head there!
But tell that to my K Force Lights that have HUAGE arms.

I’ve had three sets of X0 cranks on three bikes, DH, enduro/trail and DJ/4x and I’ve had one incident with them in the 5+ years I’ve been using them (same pairs) that was when I applied a pedal to a rock at pace on my V10 (DH) and partial pulled the pedal out of the threads and ruined them. Note the crank was completely intact and the insert still in place and I hit the pedal hard enough to pull the pedal partial out of the threads. Knackered the threads completely trying to get the pedal the rest of the way out but I don’t think an alloy crank would have necessarily faired better.

80kg, tend to try and ride through things rather than over them. Have crashed them quite a lot.

MTb I have sram xx1 and some oe spesh sram ones both have been perfect
But did kill some fsa road bike ones with loose pedal thread , the road ones were never dropped and I'm 60kg on a heavy day

I had 3 sets of Next SLs that failed within a year. Two on the pedal insert and one at the crank insert.
Silverfish were really good with warrantying them but it was getting tedious to be without a bike each time; So I sold the 4th set and switched to some carbon Praxis Lyft cranks which been faultless so far (7 months in)

For context, I'm a 72kg xc racer and don't normally break stuff even though I do a fair few miles.

In answer to maxtorque’s question:

1) They broke landing a small jump. Probably half a metre off the ground and and 2 metres long at maximum. I’m glad they failed where they did as there’s a sizeable step down directly after that and I dread to think what would have happened if they let go there.
2) I’m 95KG in my kit
3) The cranks were 3 years old and had led a hard life of many, many miles on my Enduro doing everything from long XC rides to countless uplift days and everything in between.

I have no problem with parts wearing out, nothing lasts forever. It was more the failure mode that scared me, text book carbon instant death with no warning. If it had occurred somewhere less forgiving the consequences could’ve been far worse than mild annoyance!

Two sets of FSA. Pedal insert in both became loose. Just over time nothing specific.

Not nonsense at all. You can’t (currently) make pedal or axle bosses from carbon, and so they rely on bonded in aluminium sections. These sections experience massive loads which the bonding simply can’t put up with. Add in to this the galvanic corrosion that results from these two materials being in contact where there are voids in the epoxy layer, and it doesn’t stand a chance of lasting.

Carbon cranks fail with depressing frequency - almost always at the Carbon/Alu interface.

sillyoldman - Member

Add in to this the galvanic corrosion that results from these two materials being in contact where there are voids in the epoxy layer, and it doesn’t stand a chance of lasting.

That's just not true, like I say my old Noirs lasted extremely well- long enough for foot rub to kill them.

I have a Sram S220 running for 5 years with multiple crank strikes, fast rough descending and multiple chain drops which appear to have damaged them but not, and they still go strong. From what I've gathered they will either brake on there first couple of goes or never brake by their own accord.

I've seen plenty of failed carbon cranks and it's always loose pedal inserts or where the cranks are attached to the spider / BB axle so I tend to agree with sillyoldman. We are starting to get a decent selection of carbon door handles at work 😀

3 year old X0's: pedal insert on RH side went.
Friends Sworks cranks: same thing.

5 year old XX1 cranks here, 82kg kitted up and approx 3.5k miles through them and they're as good as new 8)

i always wanted some carbon cranks, tho never been able to justify the cost.
this thread has totally chenged my mind, thanks!

5 year old XX1 cranks here, 82kg kitted up and approx 3.5k miles through them and they're as good as new.

Same here although mine are looking pretty beat up these days.

Northwind - Carbon in contact with Aluminium accelerates the process of aluminium oxidiasation.

The Race Face warranty has been good here with people with carbon crank issues, only problem is the occasional wait (from day to couple of months) so you'll need to have another pair of cranks for the warranty handling!

So if I had RF ones I wouldn't worry but I don't see any reason to get them either.

sillyoldman - Member

Northwind - Carbon in contact with Aluminium accelerates the process of aluminium oxidiasation.

Yes. And? You're taking that and jumping to "it doesn't have a chance of lasting" in the face of examples where they've lasted well. It's just silly

What Northwind mentions is what I was getting at sillyoldman.

🙂

Sorry, but my exposure to them suggests that they fail at the bosses frequently. I’d love to know the warranty returns rate, but given what I’ve seen, and the experiences listed in this thread, it would be bold to suggest the failure rate isn’t way higher than aluminium cranks.
Carbon is great for making light durable tubes, it’s just that they seem to fall at the “attaching to a spindle or pedal hurdle”. Both pretty critical for cranks.
Variable bonding success combined with the corrosion issue (which you don’t think matters?)is highly likely to be behind those failures, unless you can suggest another failure mechanism?

Back in the day I had one of the first carbon crank sets from FSA. It lasted less than a year with me. Another tale of the alu pedal spline insert insert coming loose.

Most failures (esp Raceface) seem to be early in life. More manufacturing issues than corrosion imo.

sillyoldman - Member

Sorry, but my exposure to them suggests that they fail at the bosses frequently.

Yes they do but that's not the same as having no chance of lasting which is what you said