SRAM Omnium snapped....for the 2nd time!

I've snapped some Omniums on the drive side in the same spot. I'd put it down to oxidisation as the other side the peddle was stuck, they'd done about 18k miles on my winter bike.

They did and do make steel cranks.

Either spend a lot of time trawling bicycle jumble sales and find some old road cranks (you may also need to find a cottered bottom bracket) or see if you can fit some BMX cranks to your bike.

They are designed to have a lot of power put through them by people with massive thighs riding on top of wooden boards.

You are either cranking out too many watts, banged them on something, or got a lemon.

with steel you usually need to use welds and get a different set of problems.

If alu works for all the track sprinters in the world I think they're fine for the rest of us.

Yeah steel bmx cranks can still rust, and do still snap.

Are there any clues on the other side of the broken bit (the small part that would have been on the other side of the pedal)? Are they clean breaks without any dirt/oxidation?

I'm not really sure. Here is a picture of the other side.

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Thanks for posting. I'm not sure either now. Clean break areas and dirty areas don't match up, but as you say it did get dirt on from the fall.
I have these and don't fancy a sudden failure, and I've also actually seen someone riding in front of me have the exact same break.

Reminder that velodromes have no rain, road salt, curbs to bunny hop off and sweet skids are frowned upon. And SRAM are fucking shit.

Difficult to see without cleaning it up properly and having it in front of me but it certainly looks like a progressive failure in which the dark surface has been exposed to the atmosphere for some time. The final clean bit on the dirty side has some ratchet marks which would have formed when large loads pushed the cracks through the remaining material each time you pushed hard on the pedals.
The whole thing looks like it originated at the point where the pedal contacts the crank arm. As the pedal bites in to the alloy it will harden the material a little, making it more prone to cracking.
I've just been out to check on mine and noticed that they do have black steel washers on, which would almost certainly prevent this type of failure.

velodromes have no rain, curbs to bunny hop off (potholes to hit at speed)

Except Herne Hill.

Where are half the threads!
The pedal ‘nut’ looks too big for the cranks, looks like there is some deformation at the edge of the nut where it contacts the cranks?

Definitely looks like a pedal washer would be a wise idea, I’ve got quite a few on sram cranks and have used them occasionally where the pedal nut is too big for the recessed hole.

Looking at the original picture, the area that the pedals contact the cranks look pretty chewed up.

I'm just gonna go put those pedal washers on my Quarq powermeter after all... 😬

Pedal washers all day everyday

Yeah. Pretty sure all SRAM cranksets need to have the pedal washer installed.

Mine came with the washers in the box so I would agree

Old topic needs a bump..
I’ve just snapped my Omniums crank left arm yesterday, after riding for many many years..great crankset. But replacement costed me £210.. forgot how expensive they are..

With this pedal insert/ thread failure I'm going to say lack of pedal washer. Seen dozens of downhill/mtb cranks broken there, usually because pedals and in and out of them a lot and tightened up by a maniac. Often you get a little tell tale burr that sticks out from beginning of the crack. Super strength cleaners don't help as they can affect alloy once a crack has started. And then impact damage, downhill + fixed both will suffer heavy pedal strike that to be honest is gonna start something happening in a crank arm.

FSA's cheapies (gossamer and or omega?) that was fitted to just about every cheap spesh from 2009 to 2016 all dissolved in one way or another given enough salt + traffic light sprints.

If anyone, ever, will be selling omnium non drive side 165 crank arm (black pref..), contact me please, will pay well.

My post today in the Pre 1950's thread in Bikes and Bits is relevant to this problem (4569).

It seems clear that it's a general problem and not limited to one or two brands. Some one above in this column mentions keeping the bike clean and speaking as some one who has found a crack in a Campag crank when cleaning, I agree with this. Clearly pedal washers are a good precaution - I remember that TA always supplied them with new cranks. Does this not happen now?

Old style steel cottered cranks do break very occasionally but it was much less of a problem.

There was one type of Raleigh crank used on some of their 'RRA' bikes which did have a reputation for failing and I have once seen a broken Chater Lea crank, but this was shown to me by a bike shop owner who clearly thought it was a very odd occurence. I've never seen any other broken steel cranks.

If you look at photos of continental racing from the 50's, it's striking that the pros were not quick to adopt cotterless - I guess this was because they preferred reliability to something they didn't trust.

I have got a couple of bikes with cotterless, but nearly all my riding nowadays is done on steel cottered cranks - I'm not trying to go fast, so I'm not bothered by a little extra weight.

This kind of failure is due to fatigue so has very little to do with the amount of force applied to the pedals. In fact, those big sprinters with massive legs do not fatigue their cranks. It is the long miles that cause this.

The reason cranks brake at that point is that the whole pedal-crank interface is a poor design.
I don't think I can explain this any better than Jobst Brandt, so I will just link to his posts and his solution.
https://www.sheldonbrown.com/brandt/breaking-cranks.html
https://yarchive.net/bike/crank_break.html

And no, this has nothing to do with overtightening. The washer also doesn't make much of a difference.

Presumably the same would apply to steel though.

Or put another way "If alu worked for all the pro cyclists in the world I think they're fine for the rest of us."

Because all those shimano groupsets with their alu cranks have been doing 30,000km a year under dudes from Lance to loopy local audaxer. Alu as a crank material is clearly fine.