How often to replace Shimano Hollowtech cranks to avoid catastrophic failure?

I’ve seen a lot of hollowtech cranks snapped in two from allegedly normal use, particularly SLX. No such thing with solid ones like deore, zee or saint it seems which I assume will bend rather than snap. Since this seems to be unavoidable with metal eventually fatiguing, how often should one replace cranks? How many miles for the average rider?

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