SamSam77

I am trying to figure out what is happening. I must be doing something wrong, but I don’t know what it could be.

Last year, I noticed that my nearly 2-year-old chain was very worn (1.5% stretch) and needed to be replaced. When I replaced it, the new chain began skipping, a lot, even under very mild to moderate peddling forces. This is not entirely surprising given the extreme chain wear and it was concluded that my cassette and front sprocket were also worn out. I replaced the entire rear cassette and middle-ring front sprocket (only the middle ring since the chain was not skipping on the larger ring and I never use the smallest ring). This fixed the problem. So, in summary, one year ago all three: chain, rear cassette, and front sprocket were replaced with brand new components. Since my negligence was to blame for the excessive wear, I resolved not to let that happen again and to be extremely diligent about chain maintenance. I took special care to keep the chain clean and lubricated as much as practical and to monitor its stretch.

Now fast forward 12 months…
I noticed that my chain now is getting close to needing replaced again. Using a wear gauge, the chain had exceeded 0.5% stretch and was getting close to 0.75% but was not quite there yet. Proactively, I replaced the chain before it got to 0.75% stretch, which I understood to be the typical “safe”-wear limit. Unfortunately, after replacing the chain, now it is skipping again when I peddle.

The skipping happens independent of the front sprocket position and occurs predominantly on my most-used rear cassette gears, which seems to indicate that it is skipping on the cassette. The chain skips most frequently under moderate and high peddling force, which indicates to me that it is not quite as bad as the problem I experienced last year with the extremely worn gears, but it is still a major problem.

What could be happening here? It cannot be normal to burn through a cassette (or at least several sprockets of a cassette) in only one year’s and one chain’s life cycle? I kept things pretty clean and lubricated, and did not even let it get to 0.75% stretch.

DrIsotope

The potential lifespan of a chain, measured in units of time, could approach infinity. Simply never install it, and it will never wear out.

How many miles does the drivetrain have on it? What conditions were ridden in? How many speeds? --a 6-speed chain is gonna outlast an 11-speed, all other things being equal.

I will personally never, ever get a year out of a chain, because I ride ~800 miles a month. Spread between several bikes, I go through 3-5 chains a year.

There is no magic number for how long a chain should or will last. Some MTB'ers get a few hundred miles out of their chains before they're done. Wizards on recumbents with 17 foot long chains might approach 10,000 miles.

SamSam77

Point taken. I did not intend to give so much emphasis on the length of time in my initial post. I recognize that this is only anectodal. If I had not ridden the bike at all for a year, everything would still be new. It is not the length of time that concerns me, it is more that the time- and usage-independent factor of chain stretch seemed to be within the acceptable margins (i.e., <0.75%) and this still occured. Maybe I get to this stretch point faster or slower than some other people, and that will be usage dependent, but that is still the "rule of thumb" replacement point, as I understood it. Is the lesson that I am supposed to be learning here that I need to replace at 0.5% stretch?

It was a 9-speed KMC X9-EPT chain on a Shimano CS-HG400-9 (11-25t) cassette.

alcjphil

Anther factor affecting cassette wear: If you almost always use only a couple of cogs, they will wear out much faster

Bill Kapaun

Most chain checkers tend to be conservative, causing people to replace prematurely.
However, maybe you have a fluke chain checker that goes against the norm?
I use a chain checker as a preliminary check because I KNOW it's conservative. IF it shows "worn", then I get my hands dirty.
Measure you chain with a ruler and calculate an actual number. basically you are calibrating the checker too, so you know what it really means.
I measure a 3' section of chain to give 3X the resolution of measuring a 1' section.
I use the 1" & 37" marks of my tape measure to avoid any error from a bent/uncalibrated end piece.

You didn't mention miles & riding conditions. If you ride in wet conditions with water/grit getting tossed on the chain you'd naturally expect a shorter life than clean/dry conditions.
IF you are heavy & mash, you may putting some hellacious stresses on some relatively small surfaces. If you never get out of the saddle, you'll probably get longer life.

You also didn't mention any cleaning/lube regime.

DrIsotope

As I still don't know what kind of mileage or conditions we're dealing with here, I'll just say that sub-$25 for a chain is a still a cheap chain. If you were wearing out KMC X11SL chains in short order, I can see that being a real problem.

As mentioned above, measure with a steel rule and not a chain checker. Chain checkers are only looking at a few links. Chain must also be measured under tension-- a completely worn out but "relaxed" chain could read as unworn.

SamSam77

I am taking as a given that my chain is worn and that the chain checker (in my case, a new Park Tool CC-3.2) is either accurately gauging the chain or, as suggested above, overestimating its stretch. I had not considered the possibility that the chain checker was underestimating the chain stretch, however unlikely that possibility may be. I will check this out tomorrow using a measuring tape and a longer segment of chain.

The fact that the chain is worn, however, is not the surprising thing to me. The chain is the "consumable" part, after all and is meant to be replaced regularly. Or at least more regularly than the other components of the drive train. However quickly I reached this state, be it X months or Y miles, to me does not seem to matter. What I did not expect was for the cassette to also wear out in the same amount of time/miles. In my mind, I thought that even though the chain and cassette both operate in the same environment (comparable levels of dirt, moisture, etc.), the cassette is more durable and the chain wears out more quickly, which can then wear on the cassette teeth to match its ever-growing stretch. Implicitly, I am assuming that the primary wear mechanism for the casette is a worn chain. If I am wrong, please correct me.

As mentioned by "alcjphil," if I am constantly using only a couple of the cogs on the cassette, these cogs will wear more quickly. I agree, and that seems to be what i have observed, with the skipping happening more frequently (but note exclusively) on these cogs. Don't think that I never change gears or anything like that; I definitely do. These extra-worn cogs are the ones in the middle of rhe cassette, which to me seems reasonable to spend more time in the middle than on the extreme ends.

base2 

I've got as few as 500 miles at 1.5%-2% stretch on my mountain bike & 2500-3000 miles at .75% stretch on my road bike. So much depends on conditions & pedaling style, there is no hard & fast rule to life expectancy.

I find I like Squirt chain wax & AbsoluteBlack chain rings. Things seem to last longer than standard mineral oil/ChainL/Wd40/Triflow, etc...

So at least 1 to 2 chains per year per bike. A cassette lasts around 3 years, & chain rings last ...I dunno, I've never worn one out. I usually just end up changing them just for kicks.

Work on a higher cadence, a well rounded pedal stroke, & avoid cross-chaining--my significant other at 70 rpm churned through a 15,000 mile set of chainrings in 1300 miles, most of which cross chained. I suspect you are similar in technique

conspiratemus1

i replace our chains when the inside-measurement blades of a caliper set to 132.60 mm will fit between two rollers. (In practice this means to open to 130 mm, drop the blades in between two sets of outer links, and open the blades until they butt up against the rollers.). If even one of several measurements reaches 132.60, replace the chain. This is actually easier than measuring between 24 rivets with a ruler but does indeed usually equate to 1/16” over 12”, or 0.5%. Measuring a longer section requires removing the chain and making sure there is enough tension in it to get an accurate measurement. Ideally you don’t want to remove a chain until you know you are going to replace it.

Even on the tandem, our cassettes last a long long time, a chain a season and a half. We shift gears a lot and I do bias toward the big ring on the larger half of the 9-speed cassette and away from the middle ring and the smaller sprockets, for that reason.

Lube only when really necessary. On a road bike, a chain should never get so dirty that you have to remove it to remove the dirt attracted to it by over-oiling. The black stuff that builds up on chains unavoidably is steel dust — it’s magnetic, try it! — from wear. If there is grit from sand, too, you are adding abrasive material to the chain that is harder than steel.

Leebo

Ummm, stuff wears out? Depends on miles and riding conditions.

Eggman84

I can understand a chain wearing out in one year, but find it odd that the cassette would be worn out after just 1 chain that was not worn beyond 0.75% (as you imply). You didn't mention which cog(s) this was happening on. If you ride on one or 2 of the smallest cogs, maybe this could happen. What cassette are you using and what cogs appear to be worn (skipping"?

Barry2 

Chain wear has to be really bad to result in skipping.
Assuming you do know how to adjust a rear derailleur.... is your hanger bent?

Barry

shelbyfv

It does seem odd that you can't get more than one chain per cassette. However, it seems that this happened before and replacing the cassette resolved it. Maybe something about your riding style, but it is what it is. I would suggest you stop preemptively replacing the chain and just ride the chain/cassette combo until it malfunctions, then replace as a pair. This isn't a good plan for most folks but might be the most economical for you.

trailangel

How many miles and what riding conditions???

SamSam77

First, the results from my tape measure chain stretch measurements...
I measured three chains: New chain (should be next to no stretch), old chain (the subject of this discussion), and very old chain (extremely worn, very bad). To measure, I tied the ends of each chain to weights (to provide tension) that were draped over the edge of a table on which the chain rested. I measured the distance between 45 or 46 outer links of the chain. I took each measurement twice, once in metric (0.5 mm) and once in imperial units(1/32") with a measuring tape stretched out (and taped) next to the chain. The results were:So the plot thickens...the actual stretch of the old chain is quite moderate when measured in such a manner. Nevertheless, the chain checker tool definitely falls through the links at the 0.5% setting (but not 0.75%), and the skipping when using the new chain is very real. As expected, the new chain is barely stretched from its ideal value (1" per period), and the very old chain is >1.5%, as I already knew from a measurement long ago.

To clarify, are you suggesting that 70 RPM is a slow pedaling cadence and chain wear would decrease at a higher cadence? I am honestly now sure what my usual cadence is but 70 RPM might not be a bad guess. I do try to avoid cross-chaining. Perhaps I can use the cogs on which the chain is skipping the worst now as some kind of indicator of this, in which case my most worn cogs are right in the middle of the cassett when I am using the middle front sproket (i.e., not cross-chained).

Exactly, that's what I a having a hard time understanding too. Under "normal' wear and tear conditions, one might expect the cassette to last through several chain replacement cycles, from new to some upper threshold (say 0.75%) multiple times, while here mine only lasted 1 cycle, or perhap even less.
The chain skipping happens more frequrntly in the middle of the cassette and less frequently (barely at all) at the extreme big/small ends. Skipping probability is something like a bell curve centered near the middle. Nothing looks worn to the eye, but my eyes are not a good judge of such things.

I dot not have a lot of practice making such adjustments. i do not think that it is bent but I will investigate more carefully. If it is bent, would that explain why it skips on the new chain but not on the old chain? Seems like if a bent derailleur is the cause then it should skip on both chains, especially since the old chain is actually not that worn,

While it is possible that my riding style could certainly play a role here, when it happened before that was due to inexperience and lack of attention. I kept using that (very old) chain way too long without realizing it was already worn out. While paying more careful attention, I now have one chain's worth of experience in terms of trying to replace it "on time."
Going with the double replacement strategy you suggested has certainly crossed my mind now. Before replacing the chain, everything seemed to work find; I had no complains, I just replaced it to prevent untimely wear on the other parts. But if the cassette is already worn, I'd be fine just sticking the old chain back on and continuing to ride...except then I fear having to do another triple replacement in the future, where I have to replace the chain, cassette, and front sprocket(s) all together. I am not sure about the economics of that plan, not to mention the labor on my own part.

DrIsotope

As it's become pretty clear we're never going to get a "mileage and conditions" related answer,

davidad

https://www.sheldonbrown.com/brandt/chain-care.html

base2 

Yes. That is exactly what I am suggesting. The higher the rpm, the less work is done per revolution. Meaning the load on the chain/drivetrain will be lighter.

I suppose from a drivetrain wear perspective, the worst case scenario would be to stand & stomp at 40-50 rpm while climbing a steep rise or something. Conversely, a best case scenario would be absolute perfectly even 360 degree round stroke at 110 rpm. Not that anyone really achieves either. Just illustrating extremes, here.

I think you've implied (or maybe stated outright) that you have a triple. I suggest you plug your cog & crankset sizes into a gear calculator to see visually how everything relates so that you can make better choices in gear selection. I like: gear-calculator.com
I set it to imperial units, & gear inches because that is what makes the most sense to me.

I suggest this because with triples, (or particularly flat locations) it's not uncommon to leave the cassette in 1, 2, or 3 gears in the back & then use it as a 3 speed by shifting the crankset. This obviously disproportionatly affects the 3 favored cogs. If you combine this with a slower & more piston like pedal stroke, we may have a recipe for the kind of abnormal wear you are experiencing.

As far as actual mileage I think that is not as important at this stage. Cassettes should always last many, many chains. It's almost definitely a thing you are doing.

Base2

Edit: It's also a good idea to clean, degrease, & re-lube your chain as soon as you notice "scissoring" noises when you pedal. This can & will be as soon as 1-200 miles or sooner in some conditions.

Eggman84

We all are assuming the :skipping" is happening on the cassette. But chainrings also wear, particularly because they are typically made of aluminum, some can be relatively small, and frequently some riders will use just one (whereas they will use all the rear cogs though not uniformly). With the first chain so worn, there should be considerable wear of one or more of your chainrings, which will skip just as well as worn cogs with a new chain. Or as someone suggested above it could be a poorly adjusted rear derailleur, though you would expect to hear a lot of "rattling" as the chain catches on an adjacent cog even under relatively no load. Have you looked at the pictures on Sheldon Brown's website showing new and old chainring and cog teeth. Maybe of some help to compare them. Same can be done with a new component in hand and comparing it to the existing. Maybe visit your LBS and ask to compare new and old.. Final, thought, is it the freewheel slipping; I have an older Shimano XT hub and it slips randomly when first applying pressure to the pedals (after a stop r even coasting). I keep meaning to replace the freehub with a spare but it never seems to get worse the last 3 years so I just ignore it, Good luck.

SamSam77

I had not really considered this aspect too deeply before, but I follow your logic, it seems to make sense to me. It was raining today but tomorrow I will try to go out and get a more accurate estimate of my usual pedaling cadence, I know I am definitely above 40-50 RPM, and I am never out of the saddle, so at least I am not at one extreme end of the spectrum.

I have never come across such a calculator before. I will need to study it some more to make more sense of it.
As I said/implied earlier, on the front I have three spockets: big middle, and small. I never use the smallest, and I am in the middle ring about 70% of the time, shifting across a big range of the read cassette.

I am pretty certain that the skipping is happening on the rear cassette, but you are right to point out the possibility of it being somewhere else.
After replacing my very old, extremely worn chain I also replaced the old front ring and rear cassette, so they all start out as new at the same time. Now, with the new chain, the skipping happens independent of the front ring position but varies in frequency based on the rear cassette cog. To me this is a strong indicator of it being a problem with the rear cassette and not the front ring.

I inspected the derailleur carefully. it does not look bent or otherwise damaged. I don't think it is an issue here.
Also, purely coincidentally, I also have a new freewheel, installed a couple weeks before the chain replacement, so I am pretty sure that is also not a factor in the skipping.

.I agree. Mileage is a secondary consideration at this point since, as you and others have pointed out, the cassette lifetime should be much longer than a single chain's lifetime under normal circumstances. As long as the chain doesn't get too worn, one might expect the cassette to last through several chain replacement cycles. Here, the cassette didn't even last one full chain lifetime.

As you said, it might well be my pedaling style, which somehow ages the cassette much faster than the chain.
Following that line of reasoning, aside from too low of a cadence, cross-chaining and shifting under high tension would seem to be prime candidates, though I don't think I am bad offender of these actions. I will be even more mindful going forward; maybe I am doing it unconsciously.

I put the old, partially worn chain back on the bike to eliminate the skipping problem. Let's say I take the suggestion from "shelbyfv" and don't replace it or the cassette and just keep riding on it. The next thing one would expect to wear out would be the front sprocket(s). Even then, as long as everything is aging/wearing together, as a set, it will still function alright. At what point am I going to have a real problem? Eventually something is going to wear out to a point where ignorance is no longer bliss. What problem would I have far down the line? Chain breakage?

ShannonM

Some thoughts:

Which cassette did you buy? The lighter they are, the faster they wear out. This would also be true for chains, if there are significant weight differences in chains.

You said you're basically riding in three or four gears most of the time, almost always in the middle chainring. Why is this the case? If your big ring is so tall it's unusable, replace it with a smaller one and you'll use it more, which will reduce wear on your middle ring. If you're not using your inner ring at all, and you don't live where it's flat, you may want to try consciously doing so. You will have to learn to double shift, but it's not hard. Just weird at first.
I'd recommend using a gear calculator with your current setup and seeing where your gearing is and comparing it to how you ride. (I like this graphical one, because it makes the gaps and shift patterns easier to see.) You will probably notice some things that you can use going forward.

The more you can vary the gears you use and the cadence and force with which you pedal, the better overall, IMO.

--Shannon

headwind15

NEWSFLASH: Lubrication of a bicycle chain is separate from stretching. I do not care how much lubricant/ what kind/ how clean you keep your chain, if you hang an elephant from it, it will stretch more/ faster than if you were to hang a mouse from it, period. End of discussion.

SamSam77

As stated earlier, it is a 9-speed KMC X9-EPT chain on a Shimano CS-HG400-9 (11-25t) cassette, neither of which is a particularly high-end component,

Maybe I was not clear before, but to try and correct the record, no I am definitely using more than just three or four gears when riding.
On the front I have three sprockets and on the back I have a 9-sprocket cassette, so 27 possibilities. I never use the smallest ring on the front, it is just too small (too easy to pedal), so that takes me down to 18 practical possible gear combinations. Of these, I'd say I use 10 to 12 of them regularly: using the middle ring on the front with cogs 3 to 9 on the back, and the big ring on the front with cogs 5 to 9 on the back. As such, cogs 5 and 6, in the middle of the rear cassette range, get a lot of use, which is also where I experience most of the chain skip.
As to replacing the gears to get a more appropriate set of ratios for my riding style and home terrain, that is what I did last year when I replaced the cassette. Still, I should study that gear ratio calculator that you and "base2" recommended, to see what insights that might be able to offer me.

DaveSSS 

More news. Chains don't stretch. They get longer due to the wear between the pins and the bushings formed into the inner side plates. High chain tension is caused by pedaling in a too big gear at low cadence, but also due to more tension on the chain, whenever the little ring is used. Chain tension is proportional to it's diameter. If you do a lot of climbing like I do, average cadence will be lower and the time spent in the little ring will be longer.

ShannonM

So you're basically riding the bike as a 52/42 x 11-21 7-speed double? And it's the 15 and the 17 that are getting the most wear?

If all that is right, you might like the 11-21. (11-12-13-14-15-16-17-19-21 vs 11-12-13-15-17-19-21-23-25) You trade the 23 and 25 that you don't use for a 14 and a 16 that you'd probably use a lot. If you keep the triple, and there's no reason not to unless you just want a double on the bike, you have the 30/17-19-21 as bailout gears if you ever need them. Might be a good fit for the way you ride.

--Shannon