Russ Roth

Headed up to lake Ontario to visit family and do some hill climbing with my oldest, the ride was a bit of a failure. One of the steeper climbs the crank started to make a creaking noise as I stood up to climb, next thing I know the chain falls off, followed by a crunch from the rear wheel. From what I can figure, a chainring bolt must have somehow worked its way loose, not certain how since the crank is factory and I haven't used the small ring since last Oct or Nov, no real climbs on LI to warrant using it. Two of the chainring bolts ripped out of the crank, found one with lots of aluminum still attached where it ripped out. I'm guessing the other one disappeared to where ever the missing piece of chainring went to, and the smaller of the two pieces was still bolted to the crank. While I have bent chainrings on the MTB, and bent cassette cogs, this is the first time I've ever had a gear disintegrate. Either way the sudden loss of tension on the chain let the rear der whip around and the chain ended up caught in the rear wheel which ripped the rear der in half. Wheel survived with some scrapes in the black spoke finish and the chain is straight, but don't think the der is repairable. Unfortunately the parts were bought April of 2020 so outside the 3 year warranty though the bike wasn't built till the end of Aug and hasn't been my primary bike. Have to say, I'm not impressed with modern campy quality.

georges1

I am really stunned to see thisIs it the latest record or chorus stuff from 2020???

Mackers

I've had two 11S Chorus rear mechs break on me.
Top jockey wheel bolt somehow worked itself loose with predictable results.

One on its maiden ride.

Shifted up, thinking to myself, boy this is some crisp shifting, shifted down, some noise, shifted up again and suddenly got a whole lot of slack in the chain

Russ Roth

Yup, newest 12sp. Turns out this destroys both chainrings since the small on chorus bolts into the large ring. Perfectly good crank now in need of 200+ worth of chainrings.

Last year I noticed my downshifting went to crap. Front der had the outer plate snap at the curve from the top to the front. Not sure how but assume it was a kid knocking over the bike. If it wasn't so expensive to replace the whole set I would with something shimano or sram.

georges1

I prefer shimano with the dura ace 7800-7900 series of cranks because they are much more robust than campy stuff even though the dura ace 9000-9070-9100 series of crank being less aesthetic than the former versions, they are far more reliable than anything campy. I am not talking about campagnolo wheels and hubs which have a tendancy to be very fragile and finnicky as well as being not so reliable over time.

mpetry912 

golly ! that is terrible.

sorry about the warranty

if you bought from a shop, make sure the rep hears about this.

how the mighty have fallen

/markp

Barry2 

In days of old, all I wanted was Campag parts, but I'd settle for Shimano.

Now, all I want is Ultegra parts and I'll settle for Shimano!

Barry

mpetry912 

somebody whose judgement I respect said this looked like a loose fastener problem, like a loose chainring bolt.

In 40 years on the bike I have never seen a failure like that one.

Do I have it right, the outer (large) ring bolts to the crank spider and then the inner ring bolts to the outer ? Terrible design.

that is a lot of stress on those "ears" that attach to the to the crank spider.

and five attach points are more stable than 4 especially if there are side loads imposed by large chain angle

/markp

tomato coupe

Yep, sounds like a maintenance problem.

mattcalifornia

I had an issue with my Chorus 12-speed chainring bolts too. On two different rides, the bolts worked themselves loose and I dropped the small chainring. Campy replaced the whole crankset under warranty about 2 years ago, and I haven't had any problems since then. Not sure if this is a design or manufacturing issue (or both). Also not sure if they corrected it. Yours was definitely worse than mine. My chainring never broke or bent -- it just fell off. And I had no collateral damage. Other than that (admittedly serious issue), I have loved the Chorus-12 groupset.

GhostRider62

Blue loctite works pretty good

Russ Roth

You have the attachment situation right, agree 5 bolts would be better

Yeah, but not one you would look for or typically find. In ove 26 years of fixing bikes I've never seen factory chainring bolts work themselves loose. When it has happened that bolts came loose after replacing rings or a teardown for a complete clean the issue is more obvious since it effects the large ring too. These bolts only secure the small ring and I haven't needed that since last year. Gave it a tune at the end of cross season and it didn't have issues or noises at that time.

There was some form of loctite on the bolt that was still in the crank.

big john

I have had chainring bolts come loose and even fall out on a Chorus crank and a mountain bike crank. Seen a guy fold a chainring after a bolt fell out. I always use a bit of blue Loctite on chainring bolts now. I also like to go over bolts to check torque occasionally.

I had a problem with the suspension pivots coming loose on my mountain bike, even after I Loctited them and torqued them to spec. Ended up over torquing them with lots of Loctite which solved the problem.

Any assembly subject to torque or other forces will be weaker with loose or missing fasteners. In 40+ years of working on cars for a living I've seen many examples of this.

mpetry912 

seems to me there are two problems with this design.

First, four bolts (vice 5) means that the line of chord between two adjacent crank bolts subtends a larger portion of the chainring circle, that is, where the loads are applied. See the red line in the edited pic below.

As a result there is a "folding" action acting on the chainring, a side force is applied (especially on an 11 or 12 speed rear especially where chain angle or cross - chaining is large) and I can see how a crank bolt could work loose and allow this to happen. The inner ring shows evidence of folding at the failure point (see red arrows)

2nd, the use of TWO sets of crank bolts - just a very clumsy design. One set of bolts fixes the large chainring to the crank spider, and the other set mounts the inner ring to the outer. This design puts a lot of load on the "ears" of the large chainring (see red circles).

Given the prices they are asking for these parts, they should be better designed and more reliable. I'm not surprised that there is only one team at the Tour this year riding Campagnolo.

/markp

mattcalifornia

Thanks for the engineering explanation. Doesn't Shimano also use a 4-bolt pattern? I think Campy switched to this new 4-bolt when they introduced smaller/compact chainrings and needed a smaller BCD for the inner ring. I'm not saying the new design is a good design, but I think that was the reason. Previously, they used an assymetrical 5-bolt pattern with one of the bolts hidden behind the crank-arm, so it looked like a 4-bolt pattern.

What is your engineering opinion of cinch-mounted chainrings? I have an Easton crankset (same as Race Face) on my gravel bike with Wolftooth cinch-mounted chainrings in a 1x configuration.

mpetry912 

I'm just engaging in semi - informed speculation. not familiar with "cinch mounted" chainrings. post a pic, let's have a look.

/markp

mattcalifornia

Also called "direct mount." Looks like some SRAM systems use them too. Also looks like some SRAM systems use 4-bolt: https://www.wolftoothcomponents.com/...yclocross-road

mpetry912 

no opinion on those really. No experience and somewhat dependent on use case or more properly application.

/markp

Pratt

Bummer, glad you weren't hurt.
On the positive side, you can claim real animal status, with the wrecked hardware to prove it.

TiHabanero

Oh boy, I best get busy and sell my Campy 11 speed drive train! It only has 6000 miles on it and has been flawless, but its gonna fail, I just know it. I just know it. I just know it....

But wait, Shimano uses 4 bolt along with plenty of others. Hmmmmm, something else is going on here. I wonder what it could be...maintenance?

mattcalifornia

I actually think there is a design or manufacturing flaw in the 12-speed cranksets. I think the bolts don't go deep enough to get sufficient grip (I'm not an engineer, so I may not have any idea what I'm talking about). It's not maintenance though. I discussed my situation with Campy USA and 2 local Campy dealers, and all of them agreed it was some kind of defect. None of them thought maintenance had anything to do with it. BTW, I'm a huge Campy fan and have been riding their gear since the 80s. But I think this particular part is not their best work. However, since they replaced it, it's been trouble-free for 2 years.

mpetry912 

yes I think you are on to something here. when the bolts loosen to allow side play / flex on the chainrings, that's when things get ugly

you had a warranty replacement ? Care to share what happened ?

/markp

Russ Roth

Do you think shimano holds them in with no more threads than what can fit in the thickness of the chainring?
Had a better look at the large ring today, looking at the remaining bolt the chainring bolt doesn't even come close to flush with the far edge of the chainring it bolts into, That's too little thread holding things.

mattcalifornia

Not much to tell. The chainring bolts came undone causing me to drop the small chainring mid-ride. After the first time, I had my mechanic inspect it. he couldn't see anything wrong, so he put in new bolts with loc-tite. Happened again a few weeks later. I contacted Campy. They told me to take it to a specific local shop to inspect it. They sent me a new crankset and had the shop install it. That was 2 years ago, and I haven't had any problems since then.

easyupbug 

Hearing squeaking, creaking, rattle, etc. from the chainring is a common indicator of a loose bolt(s) including my son-in-laws new FC-R8000 crankset, it is just maintenance as TiHabanero said.