Opinion needed

[Dec66]

The mess didn't start at the cassette. That had nothing to do with it. The problem was at the front. Had the mess started at the cassette and the chain popped a link open back there with an open plate facing forward, it would have ripped the front derailer off but not bent the chainring. Had the chain broken open with a forward-facing open plate and it had cleared the FD, it would have hooked on the RD cage and ripped that out.

A bent chainring is a sure sign of a chain jamming between the FD and chainring. Careful examination of the FD will show the necessary scarring.

Perfectly in-plane, chainrings are extremely rigid. This can be demonstrated by standing next to the bike, pulling the front brake and jumping down on a crank. This test is done by mechanics to identify a worn rear sprocket or worn hub pawls with no ill effects on the chain or chainring.

Hang on. The only reason I mentioned the cassette is because you said (with no supporting evidence) that he's not properly engaged the gear.

So, taking your unsupported hypothesis, he's either between gears on his cassette (which would make the chain jump); he's not engaged one or other of his front rings (in which case his chain jumps, or jams); or, rarely, the chain breaks (which it did).

On no account, ever, should the ring bend, unless you're an African bull elephant.

 

[Jody]

On no account, ever, should the ring bend, unless you're an African bull elephant.

edit: Funny bit has now been edited by the mods

 

[Yellow Saddle]

Hang on. The only reason I mentioned the cassette is because you said (with no supporting evidence) that he's not properly engaged the gear.

So, taking your unsupported hypothesis, he's either between gears on his cassette (which would make the chain jump); he's not engaged one or other of his front rings (in which case his chain jumps, or jams); or, rarely, the chain breaks (which it did).

On no account, ever, should the ring bend, unless you're an African bull elephant.

Mentioning the cassette confuses the issue. Take it out of the equation. "The gear" in question is the front, not the back. I've explained the sequence of events and the implausible sequence of events.

The chain jammed and lodged between chainrings, putting it at an angle. This angle is easily exploited by an even moderate force on the pedals to create a sideways force that bends a chainring. A chainring is only 2mm thick and made from alumiinium. It is easily bent laterally - you can do that by fitting a 150mm shifting spanner over the blade and with one hand, bend it over. A bull elephant is not needed and a leg is certainly up to the job if a hand is. However, to make it bend sideways by putting an in-plane force on it is neigh impossible. I've already explained what test you can perform to attempt such a bend.

 

[Ajax Bay]

...

@User - why is it (ie what is the rationale for) your opinion that clearly the chainring is/was defective?

 

[Yellow Saddle]

That wasn't the OP, who hasn't posted since page 1.

Duly noted.

 

[Jody]

As others have pointed out, the chain ring should not have bent under the conditions described in the OP. That would indicate it was defective.

Surely if its defective due to materials or the manufacturing process there will be evidence. Same goes for damage or mis-use.

 

[mickle]

I purchased a new road bike recently from Ribble with a Shimano Ultegra Groupset. I've done about 150 miles on it, then during a ride at weekend my chain snapped and when my local bike shop looked at it they said the front large ring had also bent - they had no idea why the circumstances of the chain incident would have caused such a result and suggested I contact my bike supplier. FYI I was pulling away on a slight incline and was on large ring on front and 4 or 5 on rear cassette, when this happened.

I was told by Ribble that cause of the failure was misuse of the equipment as I was in the wrong gear and had put the chain under too much strain.

This response feels completely ridiculous to me. I would be interested what more experienced cylists think about this?

This, quite clearly, is not the whole story.

I'm no cheerleader for Shi**no - but Ultegra chain rings are mass produced by robots and are subject to very rigorous quality assurance. They don't vary. Shi**no don't produce a batch of sh!t ones on a Friday afternoon. And Ribble are clutching at straws too.

Could the failure of the chain have caused the damage to the chain ring? It could conceivably bend a tooth or two but not the ring. So nope. Could a bent chain ring cause the chain to fail? Definitely not. Which leaves us with the only likely secenario: That the event that caused the chain to fail also damaged the chain ring. or put another way; the event that bent the chain ring also damaged the chain. The bike's been dropped onto its ring or bashed by another bike's pedal.

 

[Dec66]

A chainring is only 2mm thick and made from alumiinium. It is easily bent laterally - you can do that by fitting a 150mm shifting spanner over the blade and with one hand, bend it over

Because sticking a spanner on the ring at a right angle and pushing down is just like a chain being slightly out of kilter, yes?

 

[jonny jeez]

Call me suspicious.

But a new member coming onto an internationally visited cycle forum only to complain about a particular brand.

Has a slight whiff to it.

 

[Levo-Lon]

As above...could be sour grapes

 

[MiK1138]

Call me suspicious.

But a new member coming onto an internationally visited cycle forum only to complain about a particular brand.

Has a slight whiff to it.

To be fair we can only reasonably complain about the brands we use.

 

[MiK1138]

Don't be silly now... we should be complaining about the suppliers we haven't used....

Sorry, I forgot where i was for a moment there...

 

[2clepto]

im appreciating the bickering from the senior members, it gets us to half the meat which is crucial and sometimes very very funny.

imo i think someone could have maliciously bent the chainring with a foot for some reason...ive also only had cheap £3.50 chains snap on me and i cross chain alot, preferring the flexibility at the expense of the wear, i also like to push the parts within reason to really see how far theyll go. i did most of my destructive mistakes messing with bikes when i was younger. altho a year ago i buy an ultegra chain on sale for £15, use it a few months, service hte bike, forgot the chain was in the degreaser while trying a stronger degrease mix and the chain lost all its sheen and looks a little tatty. it went back on though and is still operating very well.

i just cant see how the OP would not notice a bent chainring before the event.

i think theres alot of accuracy in what yellow saddle said and it sounds plausible.

i have had a few chainrings bent on bikes ive bought but one i remember was resting on the chainrings as it came with no wheels and i see a few people selling various bikes in this way, but the OP purchased a new bike and rode it a few months? so it can only be a event with the OP because he wouldve returned the bike when noticing the bent chainring, unless he had a bent chainring that functioned well, which i havent seen before, maybe once, i cant recall with any accuracy, but rarely if ever.

the only time ive bent a chainring is with a vice. and ive clattered a few off rocks and things.

ive had a mid range ribble racer frramset before and didnt like it.

 

[jonny jeez]

To be fair we can only reasonably complain about the brands we use.

Sure but to start an account simply to do so seem a trifle odd.

 

[2clepto]

"seem a trifle odd" lol the odd are the majority.