Campagnolo NR/SR cranksets - Has anyone on C&V actually broken one?
 

Knowing that there are probably several hundred of these cranksets in use by this group what are the real risks?

I've seen the scary photos (but heard some were machine-forced to failure by University students studying fatigue), I've read Jobst Brandt's claim to have broken more than a dozen and I have seen one actually broken by a very strong rider (who also breaks frames) and the thirty or so stitches it took to close the wound the broken end made in his calf.

Those cranksets were made for such a long time and were the only thing to have on almost any up-market bike for decades, the population of them is likely huge compared to any other specific model of crankset, so perhaps in proportion the failure rate is no higher than anything else? Or......?

I haven't done it but in my racing days I was twice on the wheel of a Campy (probably NR) crankset rider when the right crank broke. Both riders crashed. I missed both. This was in the late '70s.

Those cranks were well made, but - many have led hard lives, they have cut threads (both I saw broke at the pedal) and they are aluminum. None of them are new.

Ben

That's the thing. They were on almost every racer's bike, precisely because they are reliable. When 99% of the high mileage crowd rode campy, of course you are going to see more cracked ones. If you buy a vintage campy, it may well have crazy miles on it.

All cranks crack. I've never broken a campy, but I cracked one at the spider, and eventually retired it before it got too bad. I bought it used from an ex Italian pro, and put probably close to another 100k miles on it before this happened. So don't worry about it. Always check cranks regularly for cracks. There's often a small crack there for months before they actually snap.

AFA Jobst Brandt, first of all he was a big guy. 2nd of all he'd ride crazy single track, and regularly chainring climb over logs and stuff -- with a road bike. He could break anything.

Yes, I had a Campagnolo Crank fail at pedal hole while I was sprinting hard out of the saddle. I went down hard and broke my collar bone.
That was about 10 or 15 years ago.

Same thing happened to me. Was doing intervals, stood up for the next repeat, and next thing I knew I was going across the road with a pedal hanging from my foot that was dragging along the road. Ended up in the field adjacent to the road. Crank had snapped right through the pedal hole.No broken bones but had I been on that road a half hour earlier, I would have run into, literally, the shift change at the industrial park at the end of the road.

Neither of the two cranks that I have broken were Campag. Both were decades old — when I bought them new in the 70s - 80s I couldn’t afford Campagnolo bling parts. A Stronglight, the one that looks like Campag Record, 103 was it?, broke obliquely 2/3 the way down the shaft just as I was starting a stroke. No crash. Later the same year, a TA Cycltotouriste broke through the pedal eye as I stood to roller-coaster over an overpass. Went down hard but no injury. Being short and light, not so far and hard to fall? Broken surfaces of both cranks showed the dark-light separation implying old crack propagating slowly then suddenly, just as described for Campag failures. A dragon lives forever, but not those alloy cranks....

i’m optimIstic that the Campag cranks I have now will outlast me. But I peer at them often. And I filed the spider web prophylacticly.

Now, here’s a can of worms: do you use pedal washers, in hopes of preventing fretting (-> cracking) around the eye? Campagnolo says not to. But I do.

Important question to anyone here who reports a breakage - did your cranks:

• Break at the pedal eye?
• Break above the pedal eye, where the toe clip strap wears the arm?
• Break at the spider, where the stress cracks always show up?

-Kurt

@conspiratemus "a dragons live forever but not those alloy cranks."
That made my day!!!

I haven't personally broken one (yet), but have had people bring their broken Record cranks into the shop, so I know it really happens.

I've broken two cranks right in the middle. Not campy. I only ever broke one clean off. After that I learned my lesson and inspect cranks for cracks periodically.

Pedal eye breaks can happen. This is a known thing and has been for decades. Note that newer Sugino cranks are much beefier around the pedal eye compared to vintage cranks. Over torquing pedals is part of the problem. Not necessary and increases chance of cracking. Save the lawyer/Park specs for cheap soft thick cast cranks.

Newfangled hollowtech cranks break too, I suspect more often than vintage campy, on a miles/failures ration. Of course there isn't actual data on this.

Again, you'll see more broken campy cranks because more people used them and more miles have been ridden on them than any others. People that bought Takagi or SR cranks didn't ride 400/week for years on end.

The main “problem” is the user.

Any part made of aluminium and that is under dynamic load will fail eventually. It has a lifespan depending on, among other things, construction/design/grade/alloy/casting/forging/etc. and /load/cycles/deformation/etc. But one thing is sure - from the first day of use it deteriorates and eventually it will fail. Depending of all the above it can happen early or late in the components use.

The user of aluminium frames, cranks, stems, bars, etc. must know this and take it into account. It is the cost of lightness (one can design and construct with aluminium in a way that it will not fail in many lifetimes but then it will be heavier than using steel). The user must check for damage and/or substitute the parts before damage occurs. Think of it as maintaining a building – you can wait until the plumbing systems collapse or you maintain it by substituting parts according to a cyclic plan. To maintain the buildings functions and therefore its use and value. The main problem is the user – not realizing this.

All alu-cranks will fail – in the end and under the right (or shall I say wrong… hrmmm difficult) circumstances. The vintage Record crank was made to endure all out pro racing – but eventually it will fail. Smart mechanics substituted it regularly. It is probably less prone to failure than most cranks but was/is used harder and longer than a “lesser” crank. Why do we not hear about cheap cranks failing? Because they are not used in a manner or long enough for them to break – ending up on the scrap yard many dynamic loads before their time is due.

A component can of course also fail because of a glitch in the manufacturing process – but let us not discuss parts made after lunch on Fridays or before lunch on Mondays. Let us talk about the mass of parts that are made as they were intended.

I have never had a Record, or any other crank, fail under me. I have checked them for cracks and even if not having cracks I have substituted them when I felt my pretty face was more worth than the price for getting another set of cranks…

And I have been into building property management all my life…

Mine broke through the pedal eye. It was less than five years old at the time. Shop where I bought the bike gave me a used replacement, not because there was any notion of a warranty but because they were amused that I was able to break a crank.

Thanks, and now it’s your task to come up with a next line that scans and rhymes.😎🎶

I have no authority to say this but I suspect those cranks failed at a greater rate than that of other cranks. But! Does that mean it's an inordinate risk? No, at least not for everyone. I'm fairly light and not very strong. I would ride one. I did ride one for nearly 30 years, the same one. Brandt cited a design or materials defect compared with other cranks. I don't remember what it was, but he was a well qualified mechanical engineer,, and I'm not. If I worried about this kind of failure, I would use a different crank.

Jobst Brandt had several criticisms of general crankset design (related to pedals spindles fretting the crankarm where they mount) and mentioned the sharp-edge stress riser on the NR/SR crank at the spider (though most appear to fail at the pedal eye rather than the spider). I'm a little surprised he didn't single out the NR/SR cranks for their anodized finish - there are a number of technical papers on how anodizing can shorten fatigue life.

"spider cracks" do happen, neglect if not caught and filed clear.

From way back, if is when ankles or toe straps rub the arm, polish through the anodizing... sometimes taking away metal.
a metallurgist acquaintance asked on the material, 7000 series grades are prone to micro fractures with the type of abrasion seen with toe straps and or ankles.
I have retired cranks that exhibited too much localized "polishing".
when the non destructive testing place nearby has time they are going to apply dye and x-ray the monsters...
Things have been slowing down with the 737 Max stoppage.

I'm still not buying the notion that they were worse than other cranks from the time period. Stronglight 93/105 didn't crack, but the soft alloy caused other issues. AFAIK Brandt went directly from steel cottered to Campy NR/SR, not riding anything else until eventually switching to 7400. Like pretty much every one else. It's not like there was some big variety of choices BITD in pro level cranksets. Different time. He told me he preferred the old steel cranks. May have been an off the cuff comment.

Aluminum fatigues with enough cycles. I had worse luck with other brands.

All fair enough, but I'm hoping that those who post in reply will be kind enough to note how their cranks failed, and that they were part of the pre C-Record, Record family.

Folks cropping up in here telling half the story about their crank failure (or bringing up a crank of a completely different design and barely mentioning the difference in their horror story) make it very difficult to infer worthwhile qualitative information, and the previous thread is full of it.

By comparison, this thread's title is pretty specific to one crank. I'm just trying to put down some good ground rules for failure reporting.

-Kurt

Not a Campy, but my Dad had a spindle on an Ofmega Mistral bottom bracket snap in half in the middle of a sprint.

OK, one failure technically. Campy NR. Classic web crack. I rode it for at least a year after it got the crack, probably longer, maybe 100 miles/week. Eventually pulled it off. I've never actually seen a complete failure from the web crack, except that one that turned out to be a university fatigue test.

But isn’t it worth knowing about failures of other cranks, too? All cranks share some design features (female threads cut to receive a pedal with a flat interface prone to fretting) and are unique in other respects, e.g., spider design. And there are user factors, particularly the abrasion by toe straps and tightening force applied to the pedal, which are independent of design and maker. Yet other user factors are correlated with design and maker: cranks used for serious racing are clustered in a few models and can be expected to have higher loss rates...because they are meant to have a hard life.

Statisticians tell us that anything that can happen eventually does. (Healthy people under 30 hardly ever die of Coronavirus but a 28-y.o. doctor in training just did.). So no surprise that a few BF-ers have broken NR/SR cranks. If the answer had been zero, I would have said the polling space is either too small or is skewed against finding broken cranks, like looking for Clinton supporters at a QAnon rally.

We all “know” that “NR cranks break.” There is a certain status you get from breaking one, which ensures they will be talked about. Breaking the crank that came on a Chinese BSO, not so much. You’d lose style points for admitting you were even riding one in the first place, so you’d start out in the hole, pre-break. So ferreting out stories of other cranks breaking is important for comparison in context. You can’t make much inference from haphazard samples of convenience but still, “Any Al crank can break and driven long enough eventually will,” is more useful than “NR cranks break.”

Besides, getting us to follow ground rules is like herding cats. 🐈🐈🐈🐆

Absolutely. But again, if it's just some story about someone's crank breaking (What type? Where?), it's just a lot of pointless guesswork that doesn't do much except fan the fearmongering flames.

Status quo for any room of over 2 people.

-Kurt

Not really sure what this proves, but I too have had an NR crank develop a crack at the spider. No failure, but that's because it made creaking noises under load and so I took it off my bike.