# broken teeth on chainring



## brainer23 (Sep 6, 2012)

So this is my first bike and I bought it new from my LBS a few months ago. Maybe 2 months ago the chain occasionally starting slipping off the front chainrings while I was riding. Now the chain has a hard time shifting from little ring to big ring in the front. What sometimes also happens when the bike does finally shift, It will feel as if the chain skips a few teeth, then grabs again So I was going to bring it into my LBS to have them flip the stem and check everything over. When i was cleaning the bike I realized the teeth on the big chainring were broken and worn down. 

Can anyone help me out and maybe give me some insight as to what could have caused this. I want to go into my LBS knowing a few things about this rather than look like an idiot. Not sure If i was doing something wrong or could have been something else.

Oh BTW its a '13 CAAD10 with 105

Thanks


IMG_2889 by maiettad054, on Flickr


IMG_2888 by maiettad054, on Flickr


IMG_2890 by maiettad054, on Flickr


IMG_2892 by maiettad054, on Flickr


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## AndrwSwitch (May 28, 2009)

Your bike may have 105 other places, but that crank is not.

I actually don't think there's anything wrong with your chainring teeth beyond that I don't really like FSA. I think you're looking at the teeth that are shorter by design, in order to facilitate shifting up.

Does the chain actually slip when it's in a gear, or only during shifts? Rereading your post, it sounds like it's while you're JRA. Does it try to shift down, or skip a tooth? Who made your rear hub?


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## tihsepa (Nov 27, 2008)

Andrw is right. Those teeth are made that way. it sounds like it is a touch out of adjustment or you are trying to shift at a slow cadence under power.


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## brainer23 (Sep 6, 2012)

CRANK: FSA GOSSAMER, BB30, 53/39
HUBS: SHIMANO RS-10

chain occasionally slips when shifting

Whats JRA?

feels as if the chain is trying to settle in place on the teeth but slips and keeps slipping. If I stop pedaling and coast for a second or two, then start pedaling again the chain falls into place on the teeth better.


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## brainer23 (Sep 6, 2012)

i keep my cadence pretty high, so im guessing just needs adjustments.

so you guys think the bigger chainring is supposed to have all different sized/shaped teeth?

Thanks for the replies, I race quads so seeing teeth on the chainrings like this looked wrong


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## cxwrench (Nov 9, 2004)

your chainring is completely normal. i don't think i've ever seen a road bike w/ 'broken' chainring teeth. that just doesn't happen. there is NO WAY you've worn out any thing on that bike in 2 months. chainring teeth have different shapes and profiles all the way around the ring. usually a chainring is divided into 2 180* halves, and the shape of the teeth will change almost every tooth.


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## AndrwSwitch (May 28, 2009)

brainer23 said:


> CRANK: FSA GOSSAMER, BB30, 53/39
> HUBS: SHIMANO RS-10
> 
> chain occasionally slips when shifting
> ...


Just Riding Along. As opposed to, say, shifting.

If you're having trouble with shifting, it's a problem with adjustment of your front derailleur or technique. You need to back off a little on the power you're developing when you shift and/or tighten up your front derailleur cable a bit. At least, that's my armchair guess without seeing the bike.


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## cxwrench (Nov 9, 2004)

AndrwSwitch said:


> Just Riding Along. As opposed to, say, shifting.
> 
> If you're having trouble with shifting, it's a problem with adjustment of your front derailleur or technique. You need to back off a little on the power you're developing when you shift and/or tighten up your front derailleur cable a bit. At least, that's my armchair guess without seeing the bike.


JRA is just riding along, yes. not necessarily 'as opposed to shifting', though. shifting is a normal part of riding. JRA is invoked by industry folks to joke about bikes that were obviously crashed, run over by trains, dropped from planes, set fire, attacked by chainsaws, run into brick walls...and then the owner says "i was just riding along..."


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## AndrwSwitch (May 28, 2009)

Maybe the owner was just riding along...

in a C-130 with the cargo hatch open...

and a Bengal tiger.


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## cxwrench (Nov 9, 2004)

brainer23 said:


> i keep my cadence pretty high, so im guessing just needs adjustments.
> 
> so you guys think the bigger chainring is supposed to have all different sized/shaped teeth?
> 
> Thanks for the replies, I race quads so seeing teeth on the chainrings like this looked wrong


yes, adjustment should take care of that. i'm absolutely 100% positive your chainrings look fine.


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## MR_GRUMPY (Aug 21, 2002)

I was just riding along when my front wheel got all funny..........

Can you replace it under warranty???
.
.
.
.
.


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## logbiter (Sep 14, 2005)

echo what others said, but since you're relatively new to cycling, it sounds like you might be "cross chaining" which can cause the symptoms you describe. 

Cross chaining refers to the relative position of the chain on the front & rear cogs (or rear cogs & chainring (front)). If you have your gears set so that the chain is on the big-big or small-small cogs, you're cross chaining, setting the chain at an extreme angle on the cogs. Aside from being inefficient & noisy, this can cause the chain to rub on the front derailleur &/or chainrings and can also cause the chain to jump around.
Basically, avoid using the smallest rear cog with the smallest front ring, or the largest rear cog and the largest front ring. 

Here's an image from Park tool & link to article on chainline.


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## NJgreyhead (Jun 27, 2009)

brainer23 said:


> CRANK: FSA GOSSAMER, BB30, 53/39
> HUBS: SHIMANO RS-10
> 
> chain occasionally slips when shifting
> ...


Minor point, maybe irrelevant:
Pics show 50/34, not 53/39.

Was the 53/39 from the spec sheet?
Possible the crankset was changed out before the sale?


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## DrSmile (Jul 22, 2006)

I'm pretty sure Gossamer cranks use stamped chainrings. They aren't going to shift as well as machined ones. It was noticeable enough on my Centaur crank that I upgraded the rings. I'd try upgrading the big ring, that's the most important one. It's not a big deal if they're mismatched.


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## cxwrench (Nov 9, 2004)

DrSmile said:


> I'm pretty sure Gossamer cranks use stamped chainrings. They aren't going to shift as well as machined ones. It was noticeable enough on my Centaur crank that I upgraded the rings. I'd try upgrading the big ring, that's the most important one. It's not a big deal if they're mismatched.


you're gonna look at those chainrings in the photos and say they're stamped? :shocked:


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## UrbanPrimitive (Jun 14, 2009)

cxwrench said:


> you're gonna look at those chainrings in the photos and say they're stamped? :shocked:


Took the words right out of my mouth. As for broken chainring teeth, I have seen it. Once. Still don't know how the guy did it as he never gave anyone a straight answer. Then again he was pretty loaded at the time so I'm not surprised. He said he "might have hit it on that curb or something". Definitely a JRA moment.


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## brainer23 (Sep 6, 2012)

Took it to my LBS and explained the situation. He brought it to the shop area and said the derailleur was a little out of adjustment. Now i was thinking that out of adjustment could be his preference compared to another mechanics, right?

And i was looking at what logbiter said and i do find myself doing this at times. But my LBS said that cross chaining would not cause my chain to fall off, just prematurely wear and damage the components. Hopefully him readjusting the derailleur solved the problem... Time will tell.

Thanks for your help guys


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## AndrwSwitch (May 28, 2009)

My MTB's big ring is missing a few teeth. Generally rock strikes. Interestingly, they're mostly gone from the part of the ring that faces down when my right foot is front. I wonder which of my feet is dominant...

Actually hasn't effected the function yet, except for one that broke a little jaggedly and needed to be dressed with a file.


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## Jwiffle (Mar 18, 2005)

brainer23 said:


> Took it to my LBS and explained the situation. He brought it to the shop area and said the derailleur was a little out of adjustment. Now i was thinking that out of adjustment could be his preference compared to another mechanics, right?
> 
> And i was looking at what logbiter said and i do find myself doing this at times. But my LBS said that cross chaining would not cause my chain to fall off, just prematurely wear and damage the components. Hopefully him readjusting the derailleur solved the problem... Time will tell.
> 
> Thanks for your help guys


Out of adjustment is out of adjustment. Most likely it just needed a turn or two of the barrel adjuster to take some slack out of the front derailleur cable. It's not a preference thing...if it's adjusted properly, it will shift smooth; if it's out of adjustment, it will shift poorly. Cables stretch (or housing settles, whichever you want to call it), etc, and so the derailleurs need adjustment from time to time to keep functioning properly.


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## brainer23 (Sep 6, 2012)

Thanks for everyone input. Went for a ride after LBS adjusted the derailleur and problem has been solved! Bike shifts great and im trying not to cross chain now.


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## Mr. Versatile (Nov 24, 2005)

The front shift is always going to be harder to execute than the rear. Pedaling slowly (slow cadence) will make it more difficult as will trying to shift when climbing a hill. For a smooth shift between chain rings you need to be pedaling at fairly fast rpm, ease off the pedals, but don't stop pedaling, then shift.


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