# Broken teeth on cassette??



## tystevens (Jul 10, 2008)

Had a new chain, der. hanger and some maintenance done on my bike at the new LBS last wednesday (spent more than I wanted b/c they apparently only had a DA chain in stock and I wanted it done and ready to go for my trip). My bike has a newer Ultegra cassette which I had put on last September. The tech had the bike up on the stand looking at what needed to be done, said the cassette looked fine, and I told him it was fairly new and should be ok. Picked up the bike and went out of town. Drove Thursday, so no riding. Took off on a ride I'd been looking forward to doing early Friday (around Bear Lake on the Idaho/Utah border, about 51 miles -- fun ride!). After about 2 miles of going thru the little town at a slower pace, I got out on the road and started to crank a little bit. Immediately I noticed that there was a problem with my 3rd smallest cog holding the chain -- I got off to look at it is missing 3 teeth -- broken right off. I didn't hear or feel anything that I could interpret as the teeth breaking off. Bummer. I completed the ride, but it was incredibly annoying (that cog puts me right at 18mph w/ a comfortable cadence, and as the ride is quite flat, it was the cog I would have used the most!) I called the LBS this morning -- tech said he didn't remember anything but to bring it in and they'll look at it.

Any ideas what could have caused this? Could I have broken them just by pedaling or did they do something at the LBS that they didn't tell me about? By the way, I rode the day before it went into the shop, and while it was shifting like crap, I didn't notice any problems with the cassette, so it either happened at the shop or in a couple miles of riding (and honestly I don't think I was on that cog at all while in the little town -- I had probably only been on it for a few hundred feet when I noticed the problem). Besides, I would be surprised and disappointed if a tech was working on my rear der. for shifting problems and didn't notice 3 teeth missing on the cassette! I don't want to be a jerk about it if it was my fault, but I just don't see how it could have broken on my ride.

Also, is it a problem to ride until it is fixed? If I just stay off that cog? I want to at least keep commuting, but I don't want to do additional damage to my new chain or anything like that.


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## EMB145 Driver (Aug 17, 2006)

Could you have bumped the wheel or bike while loading/unloading for your trip? I'd guess you'd be more likely to break off teeth that way than with normal riding.


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## tystevens (Jul 10, 2008)

Thanks for the response. I guess that is kind of my question -- could this have happened riding or was it likely from another cause?

I don't recall anything unusual while loading/unloading. But I'm quite certain nothing unusual happened on my ride before I noticed the problem.


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## JimP (Dec 18, 2001)

Could you show us a picture of the cassette?


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## FatTireFred (Jan 31, 2005)

truly broken off or "profiled"?


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## tystevens (Jul 10, 2008)

Pretty much gone -- just jagged metal where 3 teeth used to be. Certainly no profile of the old teeth left, not at all like the other teeth on the cog. Sorry, can't post picture now, maybe when I get home.


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## MR_GRUMPY (Aug 21, 2002)

Sometin's "funny" here.
I've never seen anything like this. Teeth don't break off under impact, they will bend first.
The only way I can see this happening, is if you took the cassette apart, and put a cog in a vise, and use a channel-lock to break off three teeth.


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## Dave Hickey (Jan 27, 2002)

MR_GRUMPY said:


> Sometin's "funny" here.
> I've never seen anything like this. Teeth don't break off under impact, they will bend first.
> The only way I can see this happening, is if you took the cassette apart, and put a cog in a vise, and use a channel-lock to break off three teeth.



+1 agree...

To the OP: Shimano cassette cogs have a couple of shark teeth to aid in shifting....are you sure that's not what you are looking at?


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## tystevens (Jul 10, 2008)

I wish I could post a picture. You all are being very helpful, and I got nuthin!

Are the "shark teeth" only on the 3rd smallest cog? 'Cause the 3rd smallest cog definitely looks different than the others. 

What do you think about riding it "as-is" until I get it fixed? I actually rode it to work today, taking care not to use that cog at all. What about riding it to the shop, rather than putting it on the car? Any harm to be done there?


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## spyro (Aug 3, 2004)

what is even weirder is that even missing teeth shouldn't usually mess things up too much. Broke teeth off the chainring of my MTB (in a vise trying to straighten them after bending them on a rock.) i put the chainring back on and rode it for another year


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## wim (Feb 28, 2005)

Actual broken teeth on a cassette cog are almost unheard of. As said by others, you could be looking at shifting aids, like these "shark's teeth" in the photo below. Other shifting aids are factory-twisted teeth and/or a number of shorter teeth at certain intervals among the longer ones. One company even offers "missing teeth" as a shifting aid—a large gap.


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## Tugboat (Jul 17, 2006)

It happens... I've broken teeth off cassettes before. Like you no noticeable event that it happened. At first I actually thought that my crankset was loose, but the irregular motion was only in one gear and was as a result of two teeth breaking off that cog.

I'd replace the cassette as soon as possible as it's a sign that it's pretty well worn and continuing to use it will accelerate chain wear which in turn will degrade other parts of the drivetrain.


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## California L33 (Jan 20, 2006)

MR_GRUMPY said:


> Sometin's "funny" here.
> I've never seen anything like this. Teeth don't break off under impact, they will bend first.
> The only way I can see this happening, is if you took the cassette apart, and put a cog in a vise, and use a channel-lock to break off three teeth.


Maybe the shop tech is new and accidentally did that  

I stripped 3 teeth off the ring gear of a Chevy 10 bolt rear-end once, but that was with the aid of a very serious big block.


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## wim (Feb 28, 2005)

Tugboat said:


> it's a sign that it's pretty well worn and continuing to use it will accelerate chain wear which in turn will degrade other parts of the drivetrain.


The OP's cassette is about 10 months old. Chances are good it's not worn.


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## tystevens (Jul 10, 2008)

Yeah, about 10 months and 1200 - 1500 miles on it. Its an Ultegra cassette, so it should be at least decent quality. The broken cog is probably is the cog I tend to use the most, but .... As I mentioned, the LBS tech had it up on the stand and we were looking at it to see what the shifting problems were. He said the cassette and chain rings looked fine, but the chain and der. hanger were in need of replacement.


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## Hooben (Aug 22, 2004)

It's really hard to describe to you, but could it be that your wrench has misplaced your ultegra cassette and given you a SRAM cassette. Mechanics will very often be in a rush and grab the wrong cassette and don't notice. 
SRAM cassettes work with shimano and are identified by their seemingly broken teeth on some of the cogs. They have teeth missing and curves just like the one you pictured. I hope that you have your reciept! It may be that the wrench place only one or two SRAM cogs on your cassette. Never the less that is what you have.
Look carefully at the red highlighted area and you can see the pronounced groove that you have pictured.


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## ukbloke (Sep 1, 2007)

Do you know if the mechanic took the cassette off the wheel, or had any reason to take it off? I'm wondering if inappropriate use of a chain whip on a small cog might cause this.

If it was me I'd take it back to the LBS and explain the facts without causing a big fuss, and see how they handle it. If it were me, I probably wouldn't ride the bike any more until its fixed. However, as long as the rest of the cassette looks good and you avoid that cog (and don't shift through that cog either) I don't see a problem.


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## rodar y rodar (Jul 20, 2007)

I`m waiting for the pics- I had a neighbor`s bike with one broken tooth ona her cassette and was also wondering how the heck that could happen. Granted, it was a cheapo- nothing like Ultegra, but it still posed a problem because there`s no way (not even Loose Screws) I could find another cassette to fit that hub and she didn`t want to buy a whole wheel. Yeah, wierd.


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## tystevens (Jul 10, 2008)

Update/end of the story -- I inspected the cassette a little more closely two nights ago (I took pictures, but they would not upload to RBR). The cog looks kind of like the broken one above, just with 3 consecutive cogs missing. One of the first things I noticed was that it wasn't an Ultegra cassette that was on my bike. I don't know if the LBS that installed it meant equivalent to Ultegra or what, but it was made by Miche, not Shimano. Anyone heard of that brand before? 

Anyway, I went back to the new LBS where I had work done last week, after which I noticed the problem, and discussed it with them. They said they had never seen that before, but that the Miche cassette was cheap and they didn't use them, so they weren't surprised it broke. Of course, he said he didn't break it. I said my hang-up was 2 mechanics inspected the cassette at the time I dropped it off and said it looked fine, and then the next day it was broken -- if they inspected it, what were they inspecting if not to see if the teeth were fine or in need of repair? He said they can't catch everything, and they either missed it at the time or I broke it after I left. I replied, sure, you cant catch everything, but that part was specifically inspected when I dropped it off and said it looked fine -- the one thing we know is that we had a concensus agreement by the bike shop that it was "fine" when I dropped it off. While I could have broken it after I left the shop, it also could have fallen off the stand or something while it was here. Anyway, we went back and forth for 15 minutes or so. He went and talked to the manager and then agreed to put on an actual Ultegra cassette for $70, which I agreed to. So that is what I have now. I'll try again to put up a pic tonite when I get home -- I did keep the cassette for that purpose.


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## California L33 (Jan 20, 2006)

tystevens said:


> Update/end of the story -- I inspected the cassette a little more closely two nights ago (I took pictures, but they would not upload to RBR). The cog looks kind of like the broken one above, just with 3 consecutive cogs missing. One of the first things I noticed was that it wasn't an Ultegra cassette that was on my bike. I don't know if the LBS that installed it meant equivalent to Ultegra or what, but it was made by Miche, not Shimano. Anyone heard of that brand before?
> 
> Anyway, I went back to the new LBS where I had work done last week, after which I noticed the problem, and discussed it with them. They said they had never seen that before, but that the Miche cassette was cheap and they didn't use them, so they weren't surprised it broke. Of course, he said he didn't break it. I said my hang-up was 2 mechanics inspected the cassette at the time I dropped it off and said it looked fine, and then the next day it was broken -- if they inspected it, what were they inspecting if not to see if the teeth were fine or in need of repair? He said they can't catch everything, and they either missed it at the time or I broke it after I left. I replied, sure, you cant catch everything, but that part was specifically inspected when I dropped it off and said it looked fine -- the one thing we know is that we had a concensus agreement by the bike shop that it was "fine" when I dropped it off. While I could have broken it after I left the shop, it also could have fallen off the stand or something while it was here. Anyway, we went back and forth for 15 minutes or so. He went and talked to the manager and then agreed to put on an actual Ultegra cassette for $70, which I agreed to. So that is what I have now. I'll try again to put up a pic tonite when I get home -- I did keep the cassette for that purpose.


I'd like to see the pics. Keep in mind that RBR had size limits (both pixel and memory) for pics. If you've taken it with a standard digital camera you'll need to shrink and compress it to post it.


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## JCavilia (Sep 12, 2005)

> it was made by Miche, not Shimano. Anyone heard of that brand before?


Miche is an Italian company that has been around since at least the '30's. I don't know if that particular part was cheap, but the company makes many high-quality components.


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## rodar y rodar (Jul 20, 2007)

I wonder if it could have had a hairline crack from a manufacturing defect that was somehow allowing the teeth to squirm and then finally disintegrated after the shop checked it out. That one could have easilly been missed by the mechanics, but I can`t imagine them not noticing three missing teeth while they were specifically checking for a drive train problem.


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## tystevens (Jul 10, 2008)

I took the pics with my wife's nice Canon digital SLR. I put it on the lowest setting, but maybe that was still too big. I tried to use the cheap pocket camera, but it wasn't focusing on the teeth very well at close range. I'll play around with it tonite.

As far as the Miche part, I paid $80 or $90 for it last year. The new LBS said it was kind of a unique set-up where all of the cogs were replaceable, mostly for unique gearing setups. Rather than wait for them to special order a single cog for $20 or so, I didn't want to be without my bike for a week, so I just had them throw the Ultegra part on there so I can get back to riding. Oh well, water under the bridge, I guess ...


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## Lowend (Mar 29, 2002)

Do you have the receipt for the Ultrega you thought they installed last year? Get the exact wording and if it says Ultrega, question them on that.
I hope you have other LBS in your area. I wouldn't be happy with thier response.


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## Doolab (Feb 13, 2008)

Have you considered that maybe your new DA chain was responsible for the broken teeth? seeing how the new chain would not have been worn with the cassette, and if there was even a slight mismatch between the chain and the cassette teeth profile, it may have stressed the cog and snapped those teeth.... Just some food for thought.


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## tystevens (Jul 10, 2008)

To Lowend: No, I don't have the receipt. No, I'm not going back to that particular shop anymore. Nothing they ever fixed was ever fixed, and I got tired of going back to get things re-adjusted. The owner is a nice guy, and I'd love to keep giving him business, but enough was enough. I went to this new place in part b/c it is close to my work (if I need anything and am commuting on the bike, I can just swing by), and in part b/c they sell both Specialized and Felt bikes, and the two bikes I covet the most right now happen to be the Roubaix and the Z25. So I thought they might be good to get to know. I don't know ... I was happy enough with the new LBS's response and deal on the new cassette -- I'll probably go back to them, but yeah, a little frustrated. I'm reasonable enough to see their point of view, too -- they missed the broken teeth when the bike came in, and should have caught that, but the damage didn't happen while in the shop, so it wasn't their fault. I don't know for certain the damage wasn't there when I dropped it off -- I'm not meticulous with my maintenance/cleaning/inspections (as evidenced by the fact that I thought I had an Ultegra cassette and I didn't), and possibly I had just never noticed it -- and I can't really prove anything to the contrary, except for the fact that they put at least 2 sets of eyes (plus mine) on the cassette in order to determine if it was in good shape or not, and declared that it was fine. Or maybe I broke it in the first couple miles of my ride. Who knows.

Doolab: I wondered about that, and the tech mentioned that compatibility between the cassette and chain was questionable, although upon further questioning, he had only seen incompatibility issues cause premature wear, not break teeth. He did say that Miche is more of a replacement/alternative brand for Campy parts more than Shimano, and that he doesn't know why they would have installed that cassette on my Shimano 105 spec'd bike. It seemed to occur to him to make that part of his defense after I brought up possible compatibilty questions, but he conceded that was probably not the cause after I asked him why he put an expensive DA chain on a cassette not compatible with Shimano parts. 

After taking the broken cassette completely apart, it sure looks alot like blunt force trauma than wear issues. I would think I would have noticed teeth snapping under power, and I just don't recall anything like that on my ride before the point I noticed the slippage. But who knows -- one of those mysteries that will never be answered. Like I said earlier, water under the bridge. I'm not to worried about it now -- w/ the new drivetrain parts, the shifting is snappy, the drivetrain almost silent, and I had a great ride to work this morning. That's more important than a few bucks to me!


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## wbcummock (Jul 25, 2009)

i just had a similar problem on my hack. it's really strange and i'm kinda relieved to see it isn't just me this has happened to!

i've lost loads of teeth from my favourite sprocket. maybe it has something to with metal fatigue as it is the one i use most often. the offending article is a 6 speed suntour winner freewheel. it was from the '80s but only very lightly worn.

particularly annoying as ultra-spaced 6 speed freewheels are getting harder to find at a reasonable price.


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