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Cracks in Cranks!

78 posts & 42 voices | Started 2 years ago by Buzzlightyear | Latest reply from no_eyed_deer

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Buzzlightyear - Member

Does anyone know of any fault with Shimano SLX pedals? A guy on the Commencal owners club posted up a pic of a crack in the bottom of his cranks. Mine have been creaking for a long time now so i decided to check mine and i also have the same cracks, i asked a freind who also has the same cranks and he has the cracks to! Another friend with Hones cracks has the same aswell.

These are the double version with the steel insert.

My crank:

Commie clubs members cranks:

A freinds Hone cranks that uses the same steel insert:

Cracks or something else? Could be stress marks or such like? Perfectly Normal?

Ive emailed madison but had no reply yet.

Russ

Posted 2 years ago #
coffeeking - Member

Look like cracks to me. I'll have to check mine now. I wonder what the inside shape of the arm is at that point (i.e. if it's hollow or not there). If it's not hollow there it's a very odd crack location.

Posted 2 years ago #
I_Ache - Member

Dont think I would be too happy to be riding with those sorts of cracks. Having said that I probably wouldnt notice until I landed on the top tube after a 8' drop with my pedal still attached to my foot but not the crank!

Posted 2 years ago #
sailor74 - Member

i got 3 chainsets a mixture of XT and SLX, the oldest set are about a year old the newest 3 months, all have cracks in both crank arms.

Posted 2 years ago #
woodsman - Member

It's a crack - I wouldn't use them!

Posted 2 years ago #
coffeeking - Member

Wont be long before they go pop in a painful way. Having snapped a crank arm in the past I can tell you that even on a fire-road it's not a pleasant experience!

Posted 2 years ago #
PeterPoddy - Member

Blimey. Not good at all.

Is it ONLY ones with inserts? I've got 3 pairs of Shimano cranks without them. Might check anyway.........

Posted 2 years ago #
monkeyp - Member

As a structural analyst, even I can't work that one out. you may expect then to crack 90degrees to that due to hoop stress from the thread combined with loading during use, but that is strange.

I shall get my thinking cap on...

Posted 2 years ago #
monkeyp - Member

Do all of these cranks have inserts for the pedal threads? And if so, are they threaded in, or do they look like they are freeze fitted/bonded?

Posted 2 years ago #
takisawa2 - Member

That's one of two things...it's either the flexing of the inner & outer "shells" of the arm, in effect the insert is forcing the "shells" apart when loaded; or its the "shells" pulling apart because of some inherent stresses from when the insert was put in.
You'd expect longitudinal stress to kick in way before radial hoop stress but that's usually due to internal stresses anyway.
Going to check my Hones tonight, but they were triples so dont think they have inserts.
Get someone to stand on the pedals as you look closely...

Posted 2 years ago #
whytetrash - Member

I feel a recall coming on....checks 17yr old Graftons...yep still fine :lol:...weren't SLX the "thinking mans" XTR last week?

Posted 2 years ago #
monkeyp - Member

Is the arm made up of two longditudinal sections then? Where is the split line. I thought they were hollow forged - which then raises another question - where is the forging split line.

I don't believe that the thread will pull the two sections apart - in fact it will have the opposite effect as it will tend to pull them together against the 'head' of the pedal. However the flexing of the crank away from the frame could place the split line into shear.

Posted 2 years ago #
coffeeking - Member

monkeyp - I was thinking along the same lines. Odd isn't it. If I get chance and can find a diagram of the internal structure I might model it for a bit of "fun".

Posted 2 years ago #
Buzzlightyear - Member

All the cranks i have seen with these cracks so far have been ones with the steel inserts, im not sure how my SLX inserts are fitted. I dont recall having to screw them in, my freinds hones that are cracked are press fitted in i beleive.

Id like others to check there cranks.

Posted 2 years ago #
coffeeking - Member

The split line would indeed be in shear, but I'd have thought there was mroe than enough material to deal with that problem and the insert would help rather than hinder. But if the two halves are joined and then the insert pressed in, maybe the joining and inserting process isn't quite right. Hard to tell, too many variables without seeing it all in reality.

Posted 2 years ago #
grumm - Member

Bugger just ordered an SLX Double Crankset from Merlin.

Posted 2 years ago #
lardman - Member

hmm...18st fat bloke now rushing off to check my 3 sets of Hones.

Posted 2 years ago #
STATO - Member

Ive never heard of anyone ripping the steel insert out of shimano cranks, whatever the model, has anyone else? (someone who frequents MTBR or the DH forums?). I have heard of truvativ steel insert cranks failing tho, quite a lot in fact!

Posted 2 years ago #
Buzzlightyear - Member

Ive never heard of a shimano crank snapping but by looking at the crack it could happen pretty soon to someone. Ive got this image of everyone rushing home after work tonight to check there cranks.

Posted 2 years ago #
STATO - Member

by looking at the crack it could happen pretty soon to someone

I doubt that TBH. Based on what the OP has said and the amount of people who seem to have cracks in their cranks from such a small sample group, id be amazed if it was not a reasonably common occurence, but with little/no affect on strength, hence the fact no-one has heard of any failures. Of course people should still be complaining to the shop they got them from for a replacement (certainly entitled to one id say).

Posted 2 years ago #
Daffy - Member

None of the 4 XTR cranks on my bikes are cracked. Scratched and bashed? Yes! Cracked? No.

Posted 2 years ago #
coffeeking - Member

Will check in an hour or so. No insert'd ones here though.

Posted 2 years ago #
jackal - Member

bollocks...!
Just checked my slx (double and bash) and the non drive side crank has got a crack in it approx 18mm long

I'd been bigging slx up to everyone aswell saying how strong/light they were for the money, hmmm.
I'll see if i can get a picture up in a min...

Posted 2 years ago #
jackal - Member

I've just posted it up on sdh too, looks like it could be a common problem then;

SDH linky

Posted 2 years ago #
vinnyeh - Member

double bollocks. same here, non drive side. Not a good day- cracked dropouts on Fox 36's, now this.

Probably keep riding them til a recall or somebody experiences failure

Posted 2 years ago #
jackal - Member

You can just make it out on these pics;

Looks like they're all going in the same place, in between the two 'grooves', what are these for? something to do with the steel pedal insert?

Posted 2 years ago #
vinnyeh - Member

I think this might need a new thread started with a more informative title- a lot of people who should, probably need thir attention drawn to the thread.

Posted 2 years ago #
grumm - Member

Oh arse - shiny new slx cranks sat downstairs. Now I'm scared to put them on.

Perhaps with my supersmooth riding style they will be ok.

Anyone not got cracks?

Posted 2 years ago #
stuartlangwilson - Member

No cracks on my slx with inserts. Or the old saint, new saint and diabolous cranks either, all have inserts.

Posted 2 years ago #
Onzadog - Member

Is it just the ones with steel inserts then? My XTR are fine as are the wife's XTs.

Posted 2 years ago #
Buzzlightyear - Member

Ive emailed Madison but have yet to have a reply. A new detailed thread could be in order.

Posted 2 years ago #
bungalistic - Member

Yup mine are the same as these both sides have a slight crack/fault line in them, i'll keep an eye on this thread and on the cranks to see what develops.

Posted 2 years ago #
chakaping - Member

Phew, just popped out to garage and both sides are a bit battered but uncracked.

Not done many miles on them, week in Alps and a few days back in UK, but a lot of rock bashing.

Posted 2 years ago #
chopperT - Member

Paranoia kicks in, off to shed.... cracks as above on XT770 and XT760.
What's going on?

Posted 2 years ago #
STATO - Member

.... cracks as above on XT770 and XT760

Cracks in XT? Can you confirm with pics (just to show others what to look for) as this started off as an issue only on cranks with inserts

Posted 2 years ago #