achoo

That'd only be true if the chainring bolt isn't loose or overtightened. Once there was something wrong, the longer unsupported span would make catastrophic failure more likely. There'd be a LOT more twisting at the adjacent remaining attachment points when compared to a normal 5-point attachment.

Solid_Spoke

I purchased the bike as a complete from Co-Motion, and the bike shop who is a dealer put it together. I expect this to be fully covered. No excuse for a 6 month old $4500 bike with low miles to do this. Still waiting for Bike Gallery to get back to me.

zymphad

Could you please provide evidence that the if the chainring was tightened properly, 4 arm would more likely lead to that kind of catastrophic failure than 5 arm?

They better. If I were you, I wouldn't waste any time on the phone. Your LBS and Co-Motion should cover all costs for installation, replacement and repair, crank and frame. Good luck!

vwchad

I should have been more clear. More of a chain suck than drop I suppose. I have seen a chain get jammed up so bad that it actually cracked the chain stay and bent the chainring.

If the chain had been jammed up in the wrong way, when he stood on the pedal as he started from the light it may have put a load on the chainring in such a way that it caused this damage. Just speculation of course.

DXchulo

Let's say the bolt was loose. Would that show symptoms? I'd think you'd at least skip gears or something because it would be flexing around.

vwchad

Certainly. If it was loose, it would probably creak. I've had chainring bolts get loose on my own bike. Creaks like crazy. Not sure about skipping gears though. If it was loose enough for the chainring to flex, then maybe poor shifting or some rub on the front derailleur.

Take that a step further. If it was loose enough for the chainring to flex and possibly bend, even a little, then it may have been possible for the chain to fall between the chainrings. Partly on the small chainring and partly between the two would have caused it to bind up and maybe even cause the damage we see here. I suppose it could happen.

RollCNY

Chain would not skip. It would creak up until the bolts are so loose that they are not bearing any of the load. If you only ride centered on the cassette, you could ride awhile with loose bolts and not notice. I am talking years, and you would see the bolt holes elongate when you discovered it (don't ask me how I know). If you use the full range of the cassette, you would hear chain rub against the crank sooner and against the FD sooner on each end of the cassette (the ring would pull toward the angle of load). I have never taken one to failure in this case, but you would be doing cyclic bending load with every revolution. It would not like that. It would not like that at all.

Solid_Spoke

The Bike Gallery called. Shimano is shipping a new crankset today, and that is great, but I am far more concerned about my frame. I'll get another call back by today or tomorrow with more details.

vwchad

Well that is a step in the right direction for you.

Is the frame cracked or just dented? If they can verify that it is just dented then you can probably just touch up the paint and ride on from now until forever without an issue. If it is cracked, then that is a different story.

rpenmanparker 

Isn't is rather presumptuous of you to suggest someone should be satisfied with a damaged bike through no fault of his own just because it isn't likely to asplode? I could be wrong, but I think most people reading about this would like to believe that have the cojones to get their money's worth, not willingly accept being screwed over. To be sure, nothing like that has happened yet, but your suggestion that a viable option for OP is to just touch up the ding and ride it is IMO unrealistic. Who can happily accept such a screw job?

vwchad

I did not suggest that he just roll over and say "oh well". The intent of my post was to point out that should he be denied a replacement frame or repair by Shimano, Co-Motion, or the bike shop, that all is not lost. I would have thought it was obvious... I sincerely hope that he gets it fixed or replaced, but if nobody steps up to cover the cost of the frame or repair, then what are his options? Obviously this is a worst case scenario, but I was simply trying to suggest that the frame may not be doomed to the scrap bin. To be honest, I'm surprised that I would have to explain this...

OP, I hope you have not taken my post as sugguesting that you are just going to have to deal with it. Your thread caught my interest as it seems to be an unusual, and unfortunate, failure. I've offered my opinions for possible causes of this failure simply because I found it interesting and thought that just maybe my ideas could possibly be helpful in identifying a cause for this failure and a possible solution if you are left dealing with it on your own. As I stated above, I hope things work out well in the end and that you are able to get this all fixed withouth having to shell out your own hard earned cash. Please take my previous post simply as it was intended; to provide a possible solution to a worst case scenario, that is all.

Solid_Spoke

None taken, I understood

Solid_Spoke

Co-Motion lifetime warranty does not cover "acts of God". I completely understand that...but think that Shimano should have covered it. Thankfully the Bike Gallery in Beaverton, Oregon, has excellent service! They are getting the frame repaired and repainted. I will have my Nor'wester back in 2-4 weeks. I'm relieved that this ended in a positive way. It has been a stressful ~24 hours but I can rest now. Bike Gallery has a very enthusiastic customer who has shopped there for many years and will continue to do so!

vwchad

Glad someone did!

Slackerprince

Just curious why you went with the Co-Motion brand. I looked at their site and they seem expensive.

S

vwchad

Glad to hear this will soon be behind you. That is a shop worth spending your money at, that is for sure.

Solid_Spoke

Yes, I agree it is expensive. And owning one was a dream of mine for a long time. That is why I saved. Co-Motion is handmade in Eugene, OR. I like the idea of a quality bicycle made in the US by employees paid a living wage. Their frames are expertly crafted, welded, and painted.

jland

It looks like the chainring bolt sheared off, at which point the chainring buckled and snapped near the next bolt junction. There's almost no shoulder on the crank spider where the ring attaches... if there had been a proper shoulder there, the ring might have been prevented from buckling. What model crank is this? I had a 5600 series 105 crankset for a while and it seemed that the alloy of the chainrings had a "chintzy" sound to it... like a cheap, brittle alloy.

Out of curiosity, how much force were you putting on the pedals when this happened? Were you pushing with your right leg when it snapped?

Good to hear that the mfr will fix the frame...

shelbyfv

This is an excellent resolution for you and you've certainly found a shop worth patronizing. Paying for the repair of the collateral damage is way beyond what most would expect. Congratulations!

kleng

Are bike gallery going to replace the BB , chain stay and repaint the whole frame ?
or are they going to use putty and touch up ?

Solid_Spoke

Ultegra 6800, not sure how much force was pushed exactly, and it was my left foot that drives the pedal at a stop (right foot down).

Solid_Spoke

The frame is being sent back to Co-Motion, repairs and paint will be paid for by Bike Gallery.

Slackerprince

Yeah, that's cool. Granola power!

S

fstshrk

You have not heard about shift cable fraying and breaking yet?

Other than the hydro brake problems, I heard nothing bad about the SRAM 11 speed groups.

martinus

Meh. Happened to me once, loose chainring bolt, (may have already fallen out) stoped at red light... went to push off and pedal, bam! potatochip chainring. Missing/loose bolt must have lined up, just at the wrong time, alu. chainring never had a chance. ( i'm sure a geared bike chain line, didnt help. )