New cassette worn down after only 400 miles of road use
 

I have a mid-level name-brand 11-speed carbon-fibre road bike with a Shimano 105 cassette, KMC chain, and Praxis crank. I bought the bike new from an authorized dealer 3 months ago and have put around 400 miles on it, almost entirely on paved New Jersey (read: non-mountainous) roads in good weather. I keep my bike clean and well-lubricated. I'm not a racer.

My LBS discovered that the three smallest cogs of the cassette are badly worn away, to the point that the cassette already needs to be replaced. The other cogs are like new.

The LBS says I must be using those three smallest cogs "too much," whatever that means. I'm not a particularly strong rider, so I can't imagine that I'm riding in the highest gears all that often, particularly not when I'm powering up hills and putting the most pressure on the cassette. And no, I don't cross-chain.

How can three cogs of a nearly brand-new, name-brand, factory-installed cassette be shot after only 400 miles? Does that really happen? Or could there be something wrong with the frame or another component that might have caused the cassette to degrade so quickly? I tried asking these questions to the bike manufacturer, but they told me it's really not their problem.

Only 400 miles on a 105 cassette and as you claim well lubricated and not hard use would tell me something is very wrong. As far as using cogs too much I do big ring-small cog cross chaining frequently which would cause more wear and still get around 12k miles out of a 105 10sp cassette. I'm wondering if a used cassette was on there when you bought it. Could also be a freak factory defect from Shimano. Also do a google search for "105 11sp cassette defects" or "excessive wear" etc. and see if this is a common problem with other riders.

I find this highly unlikely, I assume you took the bike back to the same store you bought it from for the "FREE new bike tune-up". Or was there a problem you noticed riding the bike? Does the chain "skip" when using these 3 cogs and pedaling under high load (standing on the pedals going uphill)? Does the drivetrain make any unusual loud noises when in these 3 cogs?

It is really hard to tell visually when a cassette is worn; there is a lot of shaping of the cogs that can be interpreted as wear when in fact they are manufactured that way to facilitate quick shifting. Before you do anything, have them disassemble the cassette and then lay the individual 3 smallest "worn" cogs next to "new" identical cogs. Bet they look the same.

If there is no shifting issue when riding, then I would go to another store and get their opinion. Better yet, find a rider you trust (and that has no financial reason to sell you something) and have them look at the cassette and ride the bike.

Ask them how long a single speed cog last and whether single speed riders use their one gear too much.

Then get them to change the cassette under warranty.

Then find a different shop.


-Tim-

+1 to all of the above. I get 6000 -7000 miles on a 105 cassette and chain, all in a hilly area, and I use the 16T cog a LOT. Even at that distance the shifting is still fine when I replace them. I don't think Superman could wear out a cassette in 400 miles. As Tim said, you need a different shop.

Nope. Not unless something is really really wrong, which you certainly would've noticed in performance. So:

1. Maybe it's not really worn out and the LBS is wrong. Probability 99%
2. Maybe the LBS put a used cassette on your new bike. Probability 1%
3. Maybe something is wrong with your new chain that caused premature wear. Probability <1%
4. Maybe it was a defective cassette that was doomed to fail regardless of your use. Probability <1%

Is your LBS the authorized dealer you bought the bike from? If not, that sounds like either they're pulling a fast one on you or simple incompetence. If they are one and the same, I'd raise the warrantee issue. Yes, those cogs are wear parts. But what they are telling you doens't happen that fast unless you really work at it.

Ben

Why is a bike with only 400 miles on it back in the shop? What problem are you trying to solve?

Odd. Why was the bike in the shop at all with such low miles on it? I trust no bad jamming of the chain at any point. Double check for any recalls on the bike or the mech. Can you post a pic of the supposedly worn cogs?

Many LBS are outstanding but our LBS is sadly known for upselling as much as they possibly can

Is a complimentary new bike check-up not something that most shops do? Or are people just not aware of the concept?

Come on, now somebody say, "You should have ridden it more before getting your free check-up."

No the "complimentary check up" is not done here. Can't imagine anyone I know taking the time to bring their bike in if there was nothing wrong with it either.

Come on, now say, "It's impossible for an LBS to use complimentary check ups to sell and upsell things you don't need..."

So why be snotty instead of posting the photo that would allow people to answer the question you posted?

Forgive me while I let the OP speak for themself in response to some reasonable questions, rather than extrapolate and guess.


It's premature of you to advocate that without knowing the terms of the assumed free check-up.

I suppose just to pile on, but I've got 4k miles on a 105 cassette and.....it's fine. Most people honestly never really wear them out.

Of course we can all understand that motivation - but the complimentary check-up up-sell is usually focused on accessories and such - very odd that they would recommend replacing a cassette on a new bike that they just sold.

I hypothesize it was one guy, very low on the experience spectrum, who didn't know what he was looking at... and hopefully not a problem with the LBS as a business.

Presuming you have a name brand bike, warranty service can be had from any dealer who handles that brand. Stores and the home office are real used to the idea that Customer X had a bad experience with Dealer Y. Bike is still under warranty.

What problems made you take it to the LBS?

400 miles is in the ball park for when I'd expect to have to adjust the front and back derailleurs on a new bike or new groupset. And for the LBS's around me, a free tune-up of the DR's and functional check of the bike as a whole is what's expected and offered by them when you buy a new bike from them.

OP here. Everybody take a deep breath, please.

To answer the question of why such a new bike would be in the shop, this was actually the second time I brought the bike in. The first time was for the 10-hour adjustment that the shop I bought the bike from recommends (and provides free of charge) to index the gears if any cable-stretching has happened and to make sure everything is honkey dorey. This time I brought the bike in because it had developed a creaking noise, and the cassette problem was an incidental finding that appears to be unrelated to the creaking because the creaking is timed to the pedal stroke and happens when going uphill and on the large cogs, not the small ones. (Let's leave the creaking issue for another thread, though. We're slowly working through the causes by process of elimination.)

After much back-and-forth, the LBS owner was able to convince Shimano to replace the cassette free of charge, but that offer came with a warning that "next time" it won't be covered. The LBS also replaced the chain, proactively, and without charge. The bike manufacturer was entirely and utterly useless, providing absolutely no support or help and totally disavowing any responsibility for their product, as if I had bought a bag of parts instead of an actual bike. (While the manufacturer has totally let me down, I have to say that the LBS seems to be acting in my best interest and is standing behind the product they sold me.)

Here are a few picture of what I'm told is the worn cassette. (EDIT: I'm told I can't post pictures because I don't have enough points, whatever that means. Oh well. Maybe this will work: The pictures of the cassette are at imgur.com/mQIMju9, imgur.com/bivMgRD, and imgur.com/bzKDXC5 .)

The bike still makes noise. That's next -- and not for this thread.

https://cimg0.ibsrv.net/gimg/bikefor...ae4f5b382c.jpg

New Shimano CS5800
https://cimg2.ibsrv.net/gimg/bikefor...b3f0af2f92.jpg

New Shimano CS 5800


Not sure that I see any wear. The pics above are my new spare that I just pulled out of the box. All I see in your pics is the normal profiling and shaping of the teeth which is alarming to those that don't realize how drastic Shimano and others get with individually profiling almost every tooth.

However the finish quality of the sprockets doesn't quite look like shimano. Are you certain that's a shimano cassette in your pics?

Here are your pics.............

https://cimg8.ibsrv.net/gimg/bikefor...9870e6c3b0.jpg
https://cimg9.ibsrv.net/gimg/bikefor...cf64479362.jpg
https://cimg1.ibsrv.net/gimg/bikefor...12d5915127.jpg

I also don't think it's possible to wear out a cassette in 400 miles, even if you were actively trying to do so. Cassette looks fine to me. And the real thing here is, if the cassette were indeed worn, the chain would be absolutely shot. If the bike shop didn't recommend replacing both, they're just trying to make a quick sale for no reason. Maybe they have a take-off 5800 cassette in the back that they'll try to put on your bike for retail.

Beyond all that, when I pull a cassette because it's noticeably worn (that is, shifting has begun to suffer,) the 11, 12, and 13 are usually in pretty good shape, because they don't get used nearly as often as the 5 cogs in the middle.

I have no reason not to trust my LBS. My bike's specs say Shimano CS-HG700-11 cassette, and I have absolutely no reason to suspect the bike shop would have installed a different cassette when they assembled the bike for me. That would be fraud, and I can't believe it would happen. The LBS has been around a long time, has several locations, and is very reputable. I didn't get to keep the old cassette (it has to be returned to Shimano for warranty coverage, per the LBS), and the black cap ring that should say "Shimano" is upside-down in all the pictures I took. But again, I can't imagine that it's not what it was supposed to be.

If you mean "knock-off," no, that didn't happen. The replacement cassette that is now on my bike clearly says "Shimano," which I never doubted, and I didn't have to pay for it.

I don't have much experience looking closely at cassettes, so I can't tell how worn the old one was. But the LBS owner and his mechanics are all very experienced, and if they tell me the inner cogs are shot, I have to believe them. Since they're sending the cassette back to Shimano for inspection, they're obviously quite certain about it.

...And that's what's so strange here. The mechanic was certain that I was riding only on the smallest cogs because those are the only ones that appeared worn to him. I know I don't do that. While it makes no sense that any cogs would wear out so quickly, it makes particularly no sense that it would be the smallest cogs. That's why I posted the question, to see if anyone has a theory how this could have happened. The bottom line is that it did happen, and I'm trying to get a handle on why.

A bad NJ LBS? I'm shocked. Okay, not really. I had a Pinarello dealer cut down a fork for me only they didn't seat it correctly in the frame. I had a colnago dealer tell me how badly my bike needed a tune up by a professional and give it back to me with the brakes so badly aligned they were squealing like a stuck pig. I've found that I'm better off buying whatever Park tool I need and just doing it myself.

Then there's the local shop I had rebuild a wheel for me. I told them I wanted back the zipp hub that came off it. They lost it instead.

I did not read all the posts, however was a new chain installed with the original cassette and tested for skipping?

Had a customer back in 1999 that bought a new Rockhopper from us to commute with. He used the bottom 3 gears. Period, never shifted to lower gears. Within 500 miles he wore them out, hooked and ugly. Smallest cogs wear the quickest, and if used the majority of the time, it will show, but I never take a cog checker or mechanic's eye for fact, I throw a new chain on and try to get those little guys to skip. If they don't then why are they judged as worn out?

Has that really been established? Your photos don't show any obvious wear.

No, I mean a take-off: someone bought a bike and had the cassette swapped, so they would put that on your bike as "new," even if it had a handful of miles on it.

If you have a new chain, or just a few links taken off of a shortened chain, you can wrap them around those cogs and find out if they are genuinely worn. If they are, the chain won't want to engage the teeth, or the chain won't sit all the way down to the bottom of the teeth. If the links slide right on, the cogs are fine.