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  1. #1
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    how long to run chain after it is stretched

    This may be a dumb question, but If I measured right tonight, my chain has stretched 1/4". It seems a lot. I have ridden about 3,000 miles approx. so far this year. I already have a new set of chainrings. I need to purchase a new cassette, or is it just cheaper to buy the individual rings on the cassette?

    So, my question, is how much longer can I run the chain on my bike knowing that it will wear down the cassette and chainring more without causing additional damage?

    Could it damage the derailleur pulley wheels if it is left on too long?
    Last edited by gholt; 08-13-10 at 12:51 AM.

  2. #2
    sch
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    Sure you measured it correctly? That is a LOT of wear, enough that likely your entire drive line will need to be replaced. Chains don't 'stretch'
    they elongate by abrasive loss of metal between the pins and rollers. See http://sheldonbrown.com/chain-life.html and the referenced article
    http://sheldonbrown.com/chains.html for further on this. If it really is worn that much, no point in worrying about more damage.
    RD pulleys are less sensitive and seem to tolerate this abuse better, but an eyeball on the thoroly cleaned pulleys should help you decide. They
    are pretty squared off when new. New cassette is cheaper than individual rings, not many places sell such.
    Last edited by sch; 08-13-10 at 01:27 AM.

  3. #3
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    Stretched 1/4 inch over what length? The commonly recommended .5% elongation is 1/16" over 12 inches of chain, but if you measured the entire chain, it would be over 1/4" longer. If you lay a 12" rule on the edge of a pin, so you can see the whole pin, the pin at the opposite end will be covered, when the chain is new. .5% elongation would expose almost half of that covered pin and 1% would expose almost the entire pin.

    The purpose of recommending the chain to be changed at that point is to avoid wearing the cogs so much that you get chain skip with a new chain. The only way to know if that has happened is to install a new chain and try it. If the most-used cogs are overly worn, the chain will skip when you pedal with a large torque ( like when you pedal standing).
    Last edited by DaveSSS; 08-13-10 at 07:59 AM.

  4. #4
    DRF aka Thrifty Bill wrk101's Avatar
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    +1 By riding the chain that long, you probably will now need to replace the cassette, chain rings, and chain. You will find out that chain is cheap. So running it past its life really doesn't save you anything, if you end up damaging other parts.

    Hard to believe it would ride at all with that much stretch, hopefully the measurement is off. I am going to assume your measurement is off, so stop riding it now, and maybe you will save some parts.

    Buy a complete cassette, there are many inexpensive ones out there if you shop a bit.

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    You may need to replace the whole drive train. 1/16" is the point where the chain should be replaced.
    http://draco.nac.uci.edu/rbfaq/FAQ/8d.2.html

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    Senior Member MudPie's Avatar
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    Quote Originally Posted by sch View Post
    . If it really is worn that much, no point in worrying about more damage..
    +1. As long as you accept the fact that if you ever put a new chain on, you'll need a new cassette, chainring, and probably pulleys, I don't see why you can't keep riding it. Eventually, something will wear and fail, but not sure if there's been any reliable studies on such wear failure. Perhaps the cycling community can use this as data point #1.

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    Assuming you measured correctly, 1/4" over 12" or 2% stretch is well past the point where you can save anything by changing now.

    You said you replaced the chainrings, if that's the case, replace the chain and cassette immediately before the new rings are destroyed.

    Or if you still have the old rings, put them back on and run the entire old drivetrain until it just won't run at all anymore. At some point it'll start skipping, and you can then replace the chain, cassette and put the new chainrings back on.

    In industry, chains and sprockets are typically run until the chain has stretched 3% at which both the chain and sprockets are replaced, so you have a ways to go. Back in the Bronze age when freewheels were cheap, we operated this way, and I've run chains until they were stretched 4-5% before they started skipping.

    Don't worry about other consequential damage, because the only other thing that might be affected are the RD pulleys and they're forgiving, and cheap anyway.

    Going forward, you have 2 basic choices:

    1- maintain good chain wear protocol and replace chains at between 1/16" and 1/8" (over 12") stretch to protect the sprockets. Usually you'll replace between 3 and 5 chains this way before the cassette wears out.

    2- run the drivetrain together as you did, as long as possible, then replace everything together.

    Which is cheaper or smarter depends on the relative cost of the sprockets vs the chains, and your willingness to be bothered worrying about it. On my own bikes, I run some one way, and some, like my beater, the other.
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    I have new chainrings. I was planning on replacing them when I make the chain change, rather than installing them on the current setup. The bike rides fine. I will take a picture to ensure that the measurement is correct. When I first saw the measurement, I thought it could not have stretched that much in 3,000 miles, but anything is possible. I will post a picture tonight.

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    Quote Originally Posted by gholt View Post
    When I first saw the measurement, I thought it could not have stretched that much in 3,000 miles, but anything is possible.
    It's an awful lot of wear in so short a time, so I suggest you take more care in your choice of lube, and chain care procedure going forward. Between the "clean and lube daily" practice which is overkill, and the never lube or clean approach, find some common sense balance, using a lube of your preference, and you should easily get 2,000+ miles before reaching 1/2% stretch, (1/16" over 12") roughly 3-4 times the life you're getting now.

    BTW- you never said if the 1/4" was over the 4' length of the chain or over 1 foot. That's a 4:1 difference and, if the former, you're experiencing fairly normal wear, and just reaching the 1/2% stretch point where most diligent folks replace their chains.
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  10. #10
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    Quote Originally Posted by FBinNY View Post
    It's an awful lot of wear in so short a time, so I suggest you take more care in your choice of lube, and chain care procedure going forward. Between the "clean and lube daily" practice which is overkill, and the never lube or clean approach, find some common sense balance, using a lube of your preference, and you should easily get 2,000+ miles before reaching 1/2% stretch, (1/16" over 12") roughly 3-4 times the life you're getting now.

    BTW- you never said if the 1/4" was over the 4' length of the chain or over 1 foot. That's a 4:1 difference and, if the former, you're experiencing fairly normal wear, and just reaching the 1/2% stretch point where most diligent folks replace their chains.
    I will have my wife measure and take a picture this morning. I think the 1/4" was over 12 rivets. It was really late, 1AM, and I hope I measured it wrong.

  11. #11
    Senior Member MrCjolsen's Avatar
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    Quote Originally Posted by wrk101 View Post
    +1 By riding the chain that long, you probably will now need to replace the cassette, chain rings, and chain.
    Quote Originally Posted by MudPie View Post
    +1. As long as you accept the fact that if you ever put a new chain on, you'll need a new cassette, chainring, and probably pulleys,
    I disagree except for the cassette.

    I've worn a lot of chains beyond their expiration point. When I've replaced them, I've had to replace my cassette as well. But I've never had a problem with chainrings or pulleys.

    What I generally do is replace my cassette about ever third or 4th chain. On the last chain, I just run it as long as I can until I start to have skipping problems.

  12. #12
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    Chain at 1/2" pitch 12 rivets is 6" .. go for 2 dozen.

    Ride it to the LBS on a replace the works shopping trip.

  13. #13
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    I can't imagine how a chain with 1/4" "stretch" over 12" would even function. I think even my puny pins could bust that.
    Riding the Ohio MS Central Ohio Challenge tour, July 12th.

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    Well, here is the pics my wife took. I don't think they are of help as she didn't get the 1" lined up in the center of the rivet.
    Attached Images Attached Images

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    It doesn't matter where you line up the start, since every part repeats every inch, so take the reading at the corresponding point.

    Looking at the pics, it appears to be nearer to 1/8" or 1% stretch. If that's the case, there's a decent chance that the cassette will be OK, unless much of your riding is done using only one or two sprockets.

    You're at a decision point, you can decide that the cassette, and rings are likely toast, and continue as you are as long as possible. Or you can replace the chain, hoping for the best regarding the cassette, but being ready to replace it if needed.

    You might base the decision on a more careful measurement, below 1/8" = replace chain; over 1/8" = too late, continue as is.

    BTW- chain measurement is best taken on the upper loop, with a bit of tension from pedal pressure to ensure all the slack is out. If measuring the lower loop, torque the RD idler cage to tension it.
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  16. #16
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    I can't believe that for as long as I have been riding bikes that I can be that inept in measuring the chain. I'll measure it again tonight to make whether or not to replace the cassette and chainring. Can you tell by the picture if the chain rings up front are in need of replacement, or could the current ones still work well.

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    Quote Originally Posted by gholt View Post
    I can't believe that for as long as I have been riding bikes that I can be that inept in measuring the chain. I'll measure it again tonight to make whether or not to replace the cassette and chainring. Can you tell by the picture if the chain rings up front are in need of replacement, or could the current ones still work well.
    Can't tell for sure from the pictures, but rings though worn look like they'll be OK.

    I never make a judgment call on chainrings and sprockets. I let the chain tell me. If it runs smoothly, they pass - if not they go.

    BTW- I can't believe I'm saying this (you should see my bikes), but if you replace the chain, spend a few minutes cleaning some of the gunk off the chainrings, and probably the cassette, so it has a fresh start.
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  18. #18
    me have long head tube TallRider's Avatar
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    I thought the chainrings looked moderately shark-finned from your pictures. but only moderately.
    here is a truly badly-worn chainring, from my impractical brother's bike after he rode estimated 10,000 miles without changing his chain. needless to say his entire drivetrain was shot.
    Attached Images Attached Images

  19. #19
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    Semi-side note, inspired by pic above: I wonder how much it would cost to pin/ramp a chainring to run in both directions. That way, as the teeth start to wear from use in one direction, you could remove it and re-install it facing the other way, and get twice the mileage out of it. As an analogy, you can do that with drive sprockets on chainsaws that have a sprocket that's separate from the clutch drum. In a manner of speaking, we only use half of the "material" of our cogs and chainrings.

    Come to think of it, was this common practice in the pre-index days, when chainrings had no pins/ramps?

  20. #20
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    Quote Originally Posted by madpogue View Post
    Semi-side note, inspired by pic above: I wonder how much it would cost to pin/ramp a chainring to run in both directions. That way, as the teeth start to wear from use in one direction, you could remove it and re-install it facing the other way, and get twice the mileage out of it. As an analogy, you can do that with drive sprockets on chainsaws that have a sprocket that's separate from the clutch drum. In a manner of speaking, we only use half of the "material" of our cogs and chainrings.

    Come to think of it, was this common practice in the pre-index days, when chainrings had no pins/ramps?
    It's one of things that makes so much sense that no one will ever do it.

    Reversing chainrings would increase service though not quite double it. Besides the pins and ramps is the problem that the bolt holes are counter-bored so the bolt head will be flush. If you counter-bored both sides there wouldn't be enough left in the middle. That could probably be designed around though.

    Many of the steel grannies used for mtb weren't counter bored and were held on with cap screws, so they could be reversed, but to my knowledge not that many people did.
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    Quote Originally Posted by FBinNY View Post
    It's one of things that makes so much sense that no one will ever do it.

    Reversing chainrings would increase service though not quite double it. Besides the pins and ramps is the problem that the bolt holes are counter-bored so the bolt head will be flush. If you counter-bored both sides there wouldn't be enough left in the middle. That could probably be designed around though.
    I flipped over the large chainring on my road bike when the teeth became too worn on one of the edges. It was a Specialized 52-tooth ring that didn't have any special ramps, so the only modification required was to knock off the pin that keeps the chain from falling between the ring and the crank. The bolt holes did have the counter-boring, so the bolt heads were sticking out slightly with it reversed, but hardly enough to notice.

    I had gotten almost 60 kmiles of use out of that ring in the original orientation and got another 35 kmiles after I flipped it. At that point it started skipping again so I replaced it with a 50-tooth ring that had previously been the small ring on another bike (wanted a larger range so I had replaced it with a 42 while it was still pretty new). This one also lacks any ramps and doesn't even have that pin that fits behind the crank so it will be easy to flip over once it gets worn down too far.

    I agree with MrCJolson that a worn chain is clearly bad for the life of the cassette/freewheel, but I haven't noticed that issue with chainrings. So once I decide that I'll be replacing the cogs I'll run the chain quite a bit longer than I would otherwise.

  22. #22
    Single-serving poster electrik's Avatar
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    Useful tips... back when i started cycling i just ran chains till the cows came home - i was baffled as to what the skipping and exploding chain was... finally the chain became too short to run and i had to replace everything

    It is a good idea to keep your somewhat worn-out chains, then you can rotate "down" the wear on a cassette/chainring until the point of exploding chains.

    If you ask me, the chain is garbage when you can't hammer the pedals w/o skipping or snappage, but rotating chains seems like a way to save cash, though admittedly i haven't worked it out.

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    Quote Originally Posted by gholt View Post
    Could it damage the derailleur pulley wheels if it is left on too long?
    The load on the derailler pulleys is low. Chain wear is probably a non-issue for these fairly-cheap-to-replace parts.

  24. #24
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    Have you priced an 11 speed chain? A bike shop might want $60-80 and the cheapest from Euro sources is around $40. Getting the same mileage from 3 chains and one cassette as others get from 6 chains saves enough money to buy the next cassette I need.

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    Put the new chain on and it seems to work fine. I haven't taken it on the road. One other Q. Can the master pin be used on the new chain and be saved as a spare master chain?

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