[Closed] How often to replace Shimano Hollowtech cranks to avoid catastrophic failure?

when and if they break at a guess.

I’ve seen a lot of hollowtech cranks snapped in two from allegedly normal use

Really?  What sort of normal use - i've never seen or heard of broken crank arms.

Never ever worried about it. Use slx and xt. Everything has some failures in a product life and a few go online to moan about them.

Just use them and if they ever fail then replace. I doubt you'll ever need to though.

Only ones I've seen broken are when shoe rub has worn them away and then they crack/snap.

The pedal threads are the first to go in my experience.

1st pic is odd, but 2nd one is worn through.

I’ve had a hollowtech bb axle crack into a comedy spiral before, but is suspect that was initiated by having to hit pedal scanners with hammers to get seized pedals off!

Probably the most prolific crank maker in the world (and SLX is probably the most common crank)? You're bound to see a few broken ones.

That last picture looks like the typical heel rub wearing through the aluminium type failure, the first two I'd put down to shit happens.

In terms of the whole bike cranks are relatively short levers made from fairly thick aluminium to get them stiff, by comparison the frame tubes are like a coke can. I've seen more frames where the whole BB has cracked (seen, not just on the internet) than I've seen snapped cranks.

N.b. zee and saint are both hollow too.

N.b.2 never actually seen a shimano crank bend or break, I have seen a truvative one snap at the bottom bracket

I think they every 10 years would be a safe bet.

1st pic is likely crash damage.

I've snapped a set. They cracked along the narrow edge, then around. Looking at the crack, they'd been cracked for a while before finally giving up while spinning around a local loop. I thought I had pictures, but I can't find them.

In their defence, they had endured 2 1/2 years of 15stone+ abusing them on a hardtail, on everything from gentle wooded local spins, to rough steep rocky descents.

Broke mine at Gisburn enduro. Were pretty old  not as worn as one in picture. Got Saints now seem a lot thicker I'll take the extra weight over the SLX. Poor things have to support 16 1/2 stone of not very careful rider.

I'm running nearly ten year old slx and not remotely worried about them snapping

N.B.N.B  Zee is not hollowtech. "The crank arms themselves are not hollow tech, so they do carry a small weight penalty compared to say SLX or XT cranks."  https://www.mtb-mag.com/en/test-shimano-zee-crank-arms/ some of the arms def don't show signs of shoe wear.

I can't find a SINGLE photo or report of a deore or zee crank arm (same non hollow arm) snapping.

have you actually snapped any your self ? or do you just had an irrational fear ?

one of our group is a serial crank breaker.hes destroyed 3 or 4 sets - 2 on 2 rides in 2 days  at one stage.

I watched him riding the devils chessboard at laggan worked out why .... he wasnt leveling pedals - he was trying to pedal down the chessboard smashing his pedal off everything.

from that i deduce that rather than replacing my cranks all the time i* would just ride without smashing my pedals into the ground every revolution.

* as someone who was a serial Square taper BB snapper.

- i have deores on my touring bike - they weigh the same as a small sun by comparison on the in the hand test 😀 - do i notice it on my tourer no.... but the same cranks on my ibis would make it a 30lb bike instead of a 29lb and some bike 😀

No I haven't, but I just ordered a slx crank going from zee and this gives me pause. I'm 190 lb and athletic. It's not irrational when it happens to people after 2 years of normal use and this type of failure can be really dangerous.

Well bloody hell. I never realised they were actually hollow!😳 I suppose the hollow tech name gives it away a bit but I always thought crank arms were solid. Never had any problems though.

It isn’t irrational but it is improbable. Especially if you’re not riding off-road or getting significant air.

you dont know what someones definition of normal use is .

the most overused phrase used in bike shops today is *was just riding along* when it shattered into a million bits.

because im a fat biff atm im 200lbs and still hasnt been an issue and most of my hollowtech cranks are 10 years old and been moved from bike to bike and dont get an easy time of it.

I've known 2 break - one was mine  one was a mate's. Both were slx, and both were being used on singlespeed bikes. I always figured it was a mix of the extra strain from one gear, and the wearing down from heel rub etc.

ZOMG!!11!

Mine have* just spontaneously snapped while the bike wasn't even moving.

* haven't.

There must be a million sets of SLX cranks out there that haven't snapped but you never get to hear about them. Makes you think, doesn't it? The government know all about it but they're trying to keep it quiet by using chemtrails and X Factor. WAKE UP SHEEPLE!!111!!!

Especially if you’re not riding off-road or getting significant air.

Most of STW then 😆

My mate lost two finger by trapping them a Ford Mondeo door. Something else for you to live in fear of.

I'm still riding a pair of XT M752 Octalink cranks (Hollowtech 1) that must be about 12-14 years old and on their 3rd or 4th frame.

I'm not a masher but they've absolutely refused to wear out (the rings have been replaced obviously); perhaps I need to upgrade for safety's sake.

I'm never sure about the lifespan of aluminium components; I'm fairly sure that my copy of Zinn and the Art ... recommends replacing stems and bars every few years but some folk seem to still ride aluminium frames that are decades old (I'm riding a pretty ancient Thomson post too).

I keep some super glue in my rucksac for when this happens, with all those pedal strikes using 26 wheels and forks on a 650b frame, mine snap at least every other ride!!!

Oh, mine are XT so you're stuffed with lowly SLX!!!

i must be dead .... im riding 10 year old carbon :O not only that it has 26" wheels and a non enduro spec top tube.

dead i tell you .... i feel those nanotube shards making their way to my heart as we speak 🙁

Sorry, didn't realise zee was solid too, when it was called Hone it was a reinforced LX crank. I'm pretty sure Saint is hollow though.

I sold a bike last year with a pair of original HTII XT cranks on it, they've been on two hardcore hardtails, an enduro bike, and two XC bikes without so much as a squeek, I suspect they'll see use on a few more frames before they die.

I never believe in replacing something to avoid a potential failure when it's perfectly good at the time, and that includes chains.

When it breaks, it breaks, then replace.

Though the few I know who break cranks seem to break a lot of things.

And is a crank break really that dangerous? When would it most likely break? On a climb I'd guess. It would be like your foot coming off the pedal. Of course if your clipped, then you've got a pedal and crank stuck to your foot, but then if you will anchor your feet to the bike... 😉

When would it most likely break?

There's a law that says it'll break at the worst possible moment.  Whilst it may be less likely, the impact of one breaking a full chat down a rock garden standing up on the pedals would be enough to make me wince.  I get round that by not thinking about it 😀

Guess not possible to design these for any possible abuse.

Important to know: aluminium will "remember" all "peak loads" / high load abuse events...

My bikes: when bending up some pedals I only replace those. Knowing that this might be not the smartest thing to do. But no crank failures yet (Deore).

I've just been out for a ride and couldn't stop thinking about those snapped crank images..... Turning right at junction, snapped crank, run over.....close to cliff edge, snapped crank, fall off cliff....climbing a steep section, snapped crank, stuck in leg, severed artery.....etc...!!!

I guess my decade old XTRs must have broken in half quite a few times by now and I just didn't notice

And is a crank break really that dangerous?

BITD, and I'm talking 1990-something here, a lad did the monster doubles at the Powder Monkey in Wallsend and his cranks (dunno which side) snapped on landing, the bit that was still attached to the bike went into his calf and he was ambulanced away :/ That is an actual true story.

BITD, and I’m talking 1990-something here, a lad did the monster doubles at the Powder Monkey in Wallsend and his cranks (dunno which side) snapped on landing, the bit that was still attached to the bike went into his calf and he was ambulanced away :/ That is an actual true story.

Same kind of injury happened to my mother-in-law (there's another story about the crank already having been broken and shoddily welded back together by father-in-law, but the injury was the same).

FWIW I've seen one SLX chainset break after about 6yrs of fairly seious abuse.  It was shoe rub that did it in though.  I must admit I'm slightly fearful of mine, which lives on my messing about/jump bike ( they're 7yrs old and I can't jump). Not enough to stop me riding them, though.

I’ve snapped SLX cranks on a hardtail. The drive side arm snapped just like the 2nd pic, not heel rub. I was on the start of vicious valley, the smooth bit before the turn off to a470. The arm litterly fell away without injury to me, before I had a chance to hammer them that day. Probably fatigue, so not really the tool for the job.

Ironically the older and heavily battered from rock strikes set of slx cranks, I took off my Aeris to fit Saint cranks, for alpine and bike park stuff are still going strong on another bike.

When would it most likely break? On a climb I’d guess.

Landing a jump. Whereupon you'd land in the saddle hard, snapping your carbon seat post and thence landing on your balls on the top tube causing g a big crash at speed....

Use Saints if you're worried.
They're easily the best crank shimano make if strength/stiffness is important to you.

Yep, snapped cranks are almost as scary as snapped bars.

That last photo isn't any sort of metal fatigue - if you look closely you can see that the crank has been rubbed down until the outer surface is literally paper-thin. It was always going to snap like this and it's probably a little unfair to blame the crank...

Note: I've replaced HT cranks because they've looked too worn to my eyes and noone wants a snapped crank. Otherwise, have used them for years and never broken one. Current pair of M9000 XTRs are unmarked and will, I assume, outlast the bike as I'm not wearing them at all.

"Landing a jump. Whereupon you’d land in the saddle hard, snapping your carbon seat post and thence landing on your balls on the top tube causing g a big crash at speed…."

Have you only got one leg ?

BB snapped jumping ye olde triple at kinoull and what happens is you end up with all your weight on the other leg. -happened to Lawr and a guy from the clan too same place different weekends raceface turbine BB's in the bad old days

Might as well keep my Zee if I'm worried, as it's non hollow and I have not read a single account of it snapping.

Or just get a non-hollowtech deore! Only 60 grams heavier than the SLX and cheaper

The new FC500 and FC600 are also not hollowtech, but they seem a tad heavier? I can't find figures anywhere.

Never ever ever seen one snapped before.

Wow, I also never guessed they were ‘that’ hollow.

TBH I’m not phased, I’ve had 3 or 4 sets now on various bikes, SLX is my ‘go to’ Crank.

ive killed two of them, but it’s usually the spline that goes. I ‘think’ it’s caused by over-tightening the Pre-load. But they seem to reach a point when they loose and if I ride them, even for a short time loose they’re goosed.

I’m never sure about the lifespan of aluminium components; I’m fairly sure that my copy of Zinn and the Art … recommends replacing stems and bars every few years

Presumably that hat depends what you’re doing; a weekly bridleway mince isn’t likely to put too much fatigue load on?

Snapped a 105 axle after about 12k miles if that counts? Never done a crank though.

Or just get a non-hollowtech deore! Only 60 grams heavier than the SLX and cheaper

Also a u section, so far more likely to flex and fatigue........ Probably why they make it heavier.

I replace all my hollowtech cranks every 2 weeks. Dura ace on road bike and xtr on the mtb just to be safe 🙂

I saw the 2 week old cranks in half before binning them so no one else maybe gets hurt !!

yohandsome

Are you saying non hollow tech cranks do not snap ever?

Are you saying non hollow tech cranks do not snap ever?

Seems like Deore non hollow tech and Zee do not snap off ever. I've tried to find any mention or photo of one snapped. Guessing they bend before they snap, allegedly deore and zee have the same arm so bending seems unlikely too.

If you google snapped crank arms there are a lot of pictures of sold snapped crank arms.

As far as I can see it’s simply a case of the right tool for the job or there wouldn’t be any point in the heavy duty versions of a crank in any group set.

I googled shimano broken crank.

most of the broken ones I could see were solid.

fwiw, i use slx cranks on my rigid surly, and i weigh 20 stone.

im not that strong, but can still exert (I imagine) a serious amount of leverage on these cranks.

they’ve been on 3 bikes and they haven’t snapped yet.

my experience, (31 years mtb, and have worked in 5 different shops) some people can break anything, but the vast majority actually break nothing.

I remember in about 1990/91, we ordered a pair of campag record cranks in for a tt specialist, he brought his bike in, we fitted them and torqued them up for him and off he went to test them out.

half hour later, he’s back, covered in cuts and grazes, blood all over the place, ‘aw man, those cranks are ****in brilliant’

we are like, ‘wtf happened to you?’

apparently, he’d been riding along and looked down to check his pedalling smoothness, and rode straight into a whole family of cyclists. On a Dual Carraigeway. 😳

Found a size 8 black Croc...

Anybody missing one?

I googled shimano broken crank.

most of the broken ones I could see were solid.

I'm counting 10 hollow ones (the seemingly solid one is a hollow 105) and 0 solid crank arms snapped.Still looking for a say post 2010 snapped solid-deore or zee crank arm.

ive killed two of them, but it’s usually the spline that goes. I ‘think’ it’s caused by over-tightening the Pre-load.

Under-tightening the two crank bolts will do this, if they come loose so does the crank wreaking the splines, the pre load does very little beyond helping installation.

Is this the stw version of flat earthers? Evidence of 10 snapped cranks mean a design issue... shimano have only ever sold 100 sets* of cranks that 10% that fail.

*i saw it on a forum post once.

Some people do over think things...

Is today actually 1st April?

I’m counting 10 hollow ones (the seemingly solid one is a hollow 105) and 0 solid crank arms <span class="skimlinks-unlinked">snapped.Still</span> looking for a say post 2010 snapped solid-deore or zee crank arm.

What does a search for unsnapped cranks come up with,what about snapped oak trees?

Is this the stw version of flat earthers? Evidence of 10 snapped cranks mean a design issue… shimano have only ever sold 100 sets* of cranks that 10% that fail.

*i saw it on a forum post once.

2 people in this thread reported snapped SLX. That's 2 out of say 500-2000 people who read the thread. Not insignificant. In 97 shimano had to do a mega recall of cranks that snapped at the pedal I believe.
Also people on trials forums warn against hollowtech so that's additional anecdotal evidence. Not really an issue though as you can get non hollowtech for less money and only 60 grams more.

I'm taking a week off the forums now..

Only a week.?

Do you work for SRAM/ Campagnolo/ FSA by any chance.?

Wasn't there some chap about 10 years ago used to collect stories and pics of carbon bikes and components that had snapped? Stuck them all in a blog.

That put a stop to carbon being used in the bicycle industry fo'shure

I’m never sure about the lifespan of aluminium components; I’m fairly sure that my copy of Zinn and the Art … recommends replacing stems and bars every few years but some folk seem to still ride aluminium frames that are decades old (I’m riding a pretty ancient Thomson post too)

I'd love to know also, although it's possibly better measured in mileage rather than time. I have had a Middleburn crank snap before but it was second hand and then on a commuter so high mileage  (I reckon about 15,000 miles)

The only cranks I have broken were SRAM  / Truvative, that spiral fracture of the spindle thing after 5 years of my 14st battering down trails.

These threads are exactly what I love about Internet forums!  Basically like allowing by of those foil hat wearing American survivalists have access to the internet!

That’s 2 out of say 500-2000 people who read the thread. Not insignificant

Incorrect. Your figures give between 0.4% and 0.1% failure rate. Are you actually saying these cranks are shit when, by your own admission, (admittedly based on made up numbers) 99.9% will be fine?

For something to be considered ‘statistically significant’, by people who know about such things, it has to be above 5%. Anything less is just down to chance. Or insignificant, if you will.

There is a reason that trials riders warn off hollow cranks.

Ever seen the front edge of a trials riders leading crank ?

Equally for failures of solid cranks Google - raceface cranks snapping.

I’m counting 10 hollow ones ....... and 0 solid crank arms <span class="skimlinks-unlinked">snapped.</span>

That's google displaying what you want to see.....

Have you tried more specific searches?

When I searched snapped crank arm, out of the first 21 hits 12 were solid, 8 hollow and 1 I couldnt tell from picture range. It looks like a problms faced by a high stress part to me, not a weakness with HT.

Incorrect. Your figures give between 0.4% and 0.1% failure rate. Are you actually saying these cranks are shit when, by your own admission, (admittedly based on made up numbers) 99.9% will be fine?

For something to be considered ‘statistically significant’, by people who know about such things, it has to be above 5%. Anything less is just down to chance. Or insignificant, if you will.

I've been a bike mechanic for 5 years (No that long, sure) and a cyclist for 30, I've got lots of mates who cycle too. I'd say thats a decent amount of experience.

I've never, ever seen a snapped crank of any type with my own eyes, none, not ever.

I'm not saying it doesn't happen, obviously it does, but it's rare. Very very rare.

I've seen bent BB axles, mashed pedal threads, bent chainrings, twisted spiders, BBs ground into the frame, inserts in carbon frames trashed (£5k Cervelo if you're interested) and HT2 LHS cranks with the serrated teeth stripped out (That's not uncommon). There's way, way more things to worry about before you get to snapped cranks!

I've got some 10 year old XT HT2 which are fine and I bought some used LX (Not SLX) ones which are fine too. But I'm not a crank-arm-rubber like some. I've still got the XT logos on my XTs.....

I have a set that are worn by heelrub significantly.  I am sure they are now a lot weaker than when they were made.  I think replacing them at some point would be prudent.

Don't assume solid arms won't snap. They're made of non-bendy aluminium, so won't just 'bend'. They'd be rubbish as levers otherwise

For ten years, I've only ever used Shimano Hollowtech cranks (SLX and XT).  Reading through this thread, it's as though I've narrowly avoided being killed to death numerous times.

A picture doesn't tell you much about whether the crank has been mashed into the ground repeatedly, or whether they've been subject to accelerated wear thanks to heel rubbage. There are various statutory bodies which will have the authority to force a manufacturer to recall products in event of safety concerns (a quick google brought up this: https://www.evanscycles.com/help/product-recall-notices)

I am troubled that the OP has started another thread with an unsupported assertion in the title.

I managed to snap an xt crank that was over 10 yrs old by rubbing my heels on it over this period, just fell off while I was riding along a canal towpath. I'd been waiting for it to go, I'd rubbed a hole in it a few months before it gave way. Replaced it with deore because that's what I had lying around in my shed.

Only other crank snapper I've known in 30 years riding is my son who in his teens snapped a solid crank on a road bike when he was in a chain gang. I had to drive 40 miles to collect him. This was 20 yrs ago.

Still, most of the things we worry about won't  happen so maybe the OP isn't so far wide of the mark

10 years in bike shops, never had any snapped hollowtech cranks in. Doing the maths that means they are 100% reliable and will never break.

I’m counting 10 hollow ones (the seemingly solid one is a hollow 105) and 0 solid crank arms <span class="skimlinks-unlinked">snapped.Still</span> looking for a say post 2010 snapped solid-deore or zee crank arm.

Hang on a moment

Snapped axle - solid crank

Bent crank - solid crank

Hollowtech failure

Guy who cut'n'shut them into a 100mm fat bike

road bike (hollowtech failure)

snapped axle

holowtech failure

road bike (hollowtech failure)

axle

axle

Seems like they're no more likely to fail than any other part of the crank, even if the sample is representative (and it was common enough to be a worry).

<Trump> AND some of those you've ticked are cutaway cranks they take to trade shows to show off their hollowness! Not failures, FAKE NEWS </Trump>

Ohh, and at the bottom of  your printscreen we have (drumroll please)

The guy replaced it with SLX.

Hmmmm, Basically 30 years in and out of the workshop. (Thats more depressing than it sounds)

I've seen about 30 snapped cranks in that time. Except when i started, state of the art was long and slender, and extremely bendy (relative to todays cranks) Think 7400 D-A and early 80's Campag Record. They used to actually snap under bigger stronger riders, or those who pedaled like they were riding a weight bench. I'd say most were in that era.

Then you have nothing much of actually snapping through normal use until the latest bonded hollowtech cranks. Where the glue joint fails and the two halves of the crank peel apart. But you can feel those going for a while before they let go.

Seen plenty were idiots have over tightened pinch bolts, or the taper bolts, or screwed the pedal in to over 40Nm, or modified the crank, or gouged it to ferk in a vice.

I’m taking a week off the forums now..

Why? Because people disagree with you?

Never seen this happening in 15 years of using Shimano cranks. As said above, most failure is from over torqued pinch bolts. Seen this happening a few times over the years, so much so that I've gave up the plastic preloader and always install alloy ones instead, far more robust from out on the trail over torqueing.

Here are some bike parts which can break during use. You should endeavour to replace each part pictured every few weeks or so to prevent the inevitable catastrophe.