What on earth? Luckily I was behind the car parked in the advance box when this happened on the morning commute.

Was later for work. Not blaming overtightening at all! I did wonder what the creak had been…

Probably suffered a bit of metal fatigue

A BIT!

In a fit of post-winter paranoia I have stripped the whole bike and an going over it with the model making torch glasses.

less mince pies for you next Chrimbo my son!! 😆

Never seen a crank snapped like that tbh, guess it could have been a latent casting defect, worth inspecting the break and look for voids / crack propagation point etc

What length is it? Assuming of course that the drive side is fine, I might have an identical 175 NDS knocking around you can have for postage.

I’ve got a mystery creak on one of my bikes….I’m worried now 😕

I’ve had that happen twice, once with a pair of L+M DH cranks in the 90’s, and then about 10 years ago a first gen Hollowtech XT, although both of mine were drive side and the first one especially may have been mostly my fault for attempting some ‘optimistic’ drops with some rather less than graceful landings…

You is a bad ass…

you should use your powerful legs fighting crime rather than snapping cranks.

Well I’ve added it to the “broken by legs” box where it joins other “unbreakable” things like Hope skewers, Renthal chainrings and V8’s.

The “broken by arses” box is more full. Full of hubs and rims and saddles.

I feel lucky it happened where it did not halfway round a berm somewhere.

Edit. Cheers bregante, I’ve already swapped it over, I have plenty spares. From having to buy stuff. That I break.

I’ve seen a few cranks snapped similar to that, mostly the cheaper group sets to be fair, usually caused by propagating cracks caused by smacking crank arms on rocks, pavements etc. Alloy does not take well to impact strikes,

Had a road crank snap across the pedal thread on me once. Stood up, mashing a VERY low cadence, in the big ring, luckily only doing about 5mph. Miraculously stayed on my feet – but it did cost me a sore right plum from the top tube landing!
The one (only!) bonus to come from the incident was that I finally ‘cured’ the creaking noise that had plagued me for months…

Me and a mate both used to ride single speed. Both snapped slx crank arms like that.

/Goes off to check 9000 mile old tatty uncared for Deore cranks on commuter

How old was the crank? It’s got me thinking about the aluminium bits on my commuter now…

Looking at the bits at either end of the crack it appears to have crumbled…

pics of fracture surfaces?