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  1. #1
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    Chain suck and dropping issues - chain line issue?

    Sorry for the long post in advance...

    Ever since I have owned my current bike, I have had issues with chain suck and drop. It's not like it happens all the time but it's often enough that it has been very aggravating and once nearly dangerous as it dropped when moving through an intersections after being stopped at a light. When it drops it gets wedged in between the cranks and frame below the chain watcher on the SRAM Force 22 derailleur.

    This has been an issue since I purchased the bike - Pinerallo FP2 with full SRAM Rival 10spd. The LBS replaced the chain rings twice in the first 3 months. I purchased a SRAM Force 22 mech with the chainwatcher and it helped with the drops. Not so much with the chain suck - but that only occasionally happens. I also noticed that for some reason it really happens most right after I clean the drive train for whatever reasons I can't understand. I have also changed the cranks for Quarq's (no difference) and had different shops look at it - they always went with change the rings or front deraillure adjustment (even so far as to start causing the chain to drop outward)...

    I've lived with it since the LBS's never fixed it. But this weekend it happened again. As I was going off on the groupset manufacture swearing that this time I'm going to replace everything with Shimano, I stopped myself and started thinking things through and I thought maybe it's been the chain line all along.

    I started thinking about chain line and how it may be my issue.

    It stands to reason by my limited understanding, that if the chainline is too wide, it would definitely work to pull the chain in. I cleaned the chain and worked with a flashlight to listen for rubbing and I think I'm rubbing a bit on the rings from the angle of the chain to the cogs when I start to get near the 3rd or 4th lowest (largest) cogs. I always thought it was derailleur rub in those combinations but there is no contact.

    Since I've never dealt with evaluating chain line, what do I need to look for or is there a way or measurement for chain line? How wide is too wide? What behavior/symptoms is/are normally associated with poor chain line?

    Thanks in advance.

  2. #2
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    It's not chainline.
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  3. #3
    Russian Troll Farmer
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    Isn't "chain suck" specifically what happens when a worn and shark-toothed chainring holds the chain under load and causes it to double-under itself? Or is the term used for other issues today?
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  4. #4
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    I've had something almost exactly similar to what you're experiencing.

    A few questions:
    1. what size are front chainrings?
    2. what size is the cassette?
    3. is the rear derailleur a med/long cage? or short cage?
    4. is the chainsuck happening when shifting from big ring to small ring as you roll over bumpy surface?

    For me, the setup that caused me to drop my chain and chainsucking was:
    1. chainrings 36/50
    2. medium cage rear derailleur with a WEAK spring (Shimano RD-5701)
    3. only happened when going from big to small chainring and over bumpy surface at a speed where I COULDN'T put full tension on the chain (ie, rolling across intersection). This would NEVER happen if I'm on an uphill where there is always chain tension.
    4. And for me, chainsuck could happen even WITHOUT the chain dropping!

    After many months of living with this condition, I've finally narrowed down the issue and solved it. The issue was that there was not enough chain tension, thus causing the chain to bounce vigorously... and if you happen to shift (big to small ring) when the chain is bouncing violently, then the chain could drop... OR... the chain could be sucked from the bottom up into the frame and the crank... the reason is because a low tensioned chain bounces in BOTH the top and bottom parts. So, I needed to raise the overall tension of the chain, and I tried these 2 ways:

    1. cut the chain shorter by a couple links. This will raise tension, however, a too short of a chain may cause too high tension when you're in the big/big combo, and this too high chain tension will result in poorer shifting, louder chain noise, and push the limits of your rear derailleur. So depending on how long your chain is now, you may or may not want to try this route. A good way to judge is to put the chain in small/small combo, and if the chain is almost sagging or showing very low tension, then you may possibly can cut 2 links off and give it a go.

    2. get an mtb derailleur where the spring tension is stronger! After trying method #1 above, I went with this method. I put on a Shimano mtb derailleur which has higher spring tension and a "clutch". Clutch can lock out the chain and prevents it from bouncing completely, but this also result in a too stiff a chain, thus causing poor shifting and higher drivetrain friction, so I never use the clutch feature. However, just the high spring tension alone of the mtb derailleur is enough to solve my chain dropping and sucking issue completely.

    So that was my case.
    Last edited by aclinjury; 3 Weeks Ago at 02:00 PM.

  5. #5
    RoadBikeReview Member
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    Quote Originally Posted by No Time Toulouse View Post
    Isn't "chain suck" specifically what happens when a worn and shark-toothed chainring holds the chain under load and causes it to double-under itself? Or is the term used for other issues today?
    Chainsuck doesn't happen on road bikes much. But I know it happens more regularly on mtb bikes with long travel suspensions. In the case of mtb, the reason why a chain would be sucked up into itself is because the mtb suspension would bounce (as you go over bumps) and this bouncing suspension would cause chain line to grow and contract violent, and the longer the suspension, the harder the chain would bounce... to the point that the chain would fall off the chainrings completely and gets sucked into the crankset/bottom area. MTB derailleurs nowaday come with clutches to mitigate this.

    On a road bike, there is no suspension travel, so chain can't grow/contract via suspension travel. However, a too low-tensioned chainline on a road bike can still cause the chain to bounce as you go over bumps... to the point that the chain could drop off the chainring (usually the small ring, because chain tension is lowered when in small ring vs. when in big ring) and gets sucked into the bottom bracket area.

    Worn out chainrings "shark tooth" does increase the chances of a chain falling off thus increase chances of chainsuck too. But IMO, the primary culprit of chainsucks is chain bouncing and this relates to mean chain tension.
    Last edited by aclinjury; 3 Weeks Ago at 02:06 PM.

  6. #6
    'brifter' is a lame word.
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    Quote Originally Posted by No Time Toulouse View Post
    Isn't "chain suck" specifically what happens when a worn and shark-toothed chainring holds the chain under load and causes it to double-under itself? Or is the term used for other issues today?
    Correct. It can happen w/ parts that aren't worn out but usually it's an old, worn chainring hanging on to a chain when you're shifting...usually from the small ring to the big ring.
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  7. #7
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    Quote Originally Posted by cxwrench View Post
    It's not chainline.
    I agree. If you're using a chain with a master link, try using a chain that uses a pin instead. For some reason I'm thinking a master link might not be playing nice with the chainrings, even though I'd expect otherwise. Just trying to think outside the box.

  8. #8
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    Quote Originally Posted by tinball View Post
    The LBS replaced the chain rings twice in the first 3 months.
    oh boy. I'll give them a mulligan on the first time but if they think you wore out a second set in less than 3 months that's probably a pretty good indication they don't know what they are doing altogether.
    Not sure about the chain suck issue but incompetence is likely the issue with the chain drops.

    Are you using a uni-directional (Shimano) chain perhaps? Check to make sure it's on the right way if that's the case. Although I highly doubt that's an issue because you would be having rear shifting issues too. Well, I did the time I spaced out and put one on backwards. I caught it before I noticed what it did to front shifting.

  9. #9
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    Thanks everyone for looking into this with me.

    I remembered one more detail that may or may not matter. Twice in the past, I have had the chain drop from back pedaling once from zeroing out the power meter and once while stopped and just moving the cranks to get the right crank arm around to a slightly lower position without picking up the rear and pedaling forward. Don't know if i that matters or not.

    I'll post some pictures below of the drive train from the side for reference if anyone sees anything glaringly wrong.

    Quote Originally Posted by aclinjury View Post
    A few questions:
    1. what size are front chainrings?
    2. what size is the cassette?
    3. is the rear derailleur a med/long cage? or short cage?
    4. is the chainsuck happening when shifting from big ring to small ring as you roll over bumpy surface?
    1)Compact 50/34
    2)Sram 11/28 (chain is a sram PG1070)
    3)Sram standard Rival 10spd - I don't think they offered different size cages for the 10spd rival group - cxwrench may know. Pictures below may confirm what size.
    4)I believe the chainsuck is occurring when going big to small. Doesn't happen often but usually when I shift under some power or decent cadence. When it happens, it's rough and sudden.

    As far as chain tension, it looks like there may be the slightest of sag in the chain (see pics) but on big-big I may have a bit more room but it may stress the derailleur too much if I take a couple of links out. What do you think based on the pic? I like to hear thought before I shorten.

    I have been considering new rings and going to semi-compact but have been concerned with losing the 34/28 gear for climbing.

    Quote Originally Posted by Peter P. View Post
    ... If you're using a chain with a master link, try using a chain that uses a pin instead.
    Quote Originally Posted by Jay Strongbow View Post
    ... that's probably a pretty good indication they don't know what they are doing altogether.

    Are you using a uni-directional (Shimano) chain perhaps? .
    It's a Sram PG1070 with master link which is directional (the link not the chain if I recall correctly). I may try a Shimano Ultegra 10spd if I have one lying around or order one.

    It went to 3 different shops - we had 4 different LBS's in my area at the time now have 3. Pretty much the same response at the 3 I went to. I think it pretty much went like this... put it in the stand, spin the cranks and shift. Check cable, adjust derailleur, take the bike for a spin in the lot. Fail to get it to drop or chainsuck. Maybe recommend new rings or new cable. Charge for work and parts.

    Chain suck and dropping issues - chain line issue?-img_2032.jpgChain suck and dropping issues - chain line issue?-img_2030.jpgChain suck and dropping issues - chain line issue?-img_2031.jpg
    Chain suck and dropping issues - chain line issue?-img_2034.jpgChain suck and dropping issues - chain line issue?-img_2033.jpg

  10. #10
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    The chain looks fine in small/small. So I don't think it needs to be shorten.

    Here is what I'm thinking on top of my head of I'd do:

    1. change out the 34t small ring to a 36t ring. Smaller difference in chainring sizes means lesser chances of a drop, but will not eliminate dropping completely.

    2. adjust the chain catcher to be as close to the small ring as possible without touching the ring. For a chain to drop and slip thru the chain catcher tells me that your chain catcher is still too far away from the small ring.

    3. if you back pedal and the chain drops, then don't back pedal. There is no guide that will prevent this. In general, if the chainling angle is great (eg, caused by short chainstays), then this will tend to happen. In fact, even before the chain drop, you can already hear that it is trying to jump out of gear on the cassette. In my case, a different chain mitigate this backpedalling-chaindrop issue (apparently I was using a KMC chain when this happened, but switching to a Shimano chain greatly mitigate this, and gave me a much quieter drivetrain too!)

    that's all I can think of for now

  11. #11
    'brifter' is a lame word.
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    Quote Originally Posted by aclinjury View Post
    The chain looks fine in small/small. So I don't think it needs to be shorten.

    Here is what I'm thinking on top of my head of I'd do:

    1. change out the 34t small ring to a 36t ring. Smaller difference in chainring sizes means lesser chances of a drop, but will not eliminate dropping completely.

    2. adjust the chain catcher to be as close to the small ring as possible without touching the ring. For a chain to drop and slip thru the chain catcher tells me that your chain catcher is still too far away from the small ring.

    3. if you back pedal and the chain drops, then don't back pedal. There is no guide that will prevent this. In general, if the chainling angle is great (eg, caused by short chainstays), then this will tend to happen. In fact, even before the chain drop, you can already hear that it is trying to jump out of gear on the cassette. In my case, a different chain mitigate this backpedalling-chaindrop issue (apparently I was using a KMC chain when this happened, but switching to a Shimano chain greatly mitigate this, and gave me a much quieter drivetrain too!)

    that's all I can think of for now
    ^This is exactly what I would post^. The chainline is what it is...you can't adjust it. It can't really be 'wrong'...the chain can have take a slightly more severe angle to the chainring depending on what gear combination you're using and a short chainstay/wheelbase can accentuate this. It's not like the old days where you had bottom brackets w/ different axle lengths for different cranks and you could actually change or adjust chainline.
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  12. #12
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    This is a tough one. I was going to recommend ACLInjury's advice of shortening the chain, however, looking at your pics, it looks like you're as short as you can go without binding in the large/large combo. So nowhere to go there.

    Are you sure the limit screws are set correctly? Yes, I know the bike shop says they adjusted them, but they from my own experience, they usually adjust those wider than necessary.

    If all else fails, the only thing I can think of to reduce the chances of this happening is to downshift to the small ring before you get into the larger cassette cogs. It is less likely to happen when in the smaller cogs.
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  13. #13
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    Is the problem the chain is dropping when going from big to small?
    That usually means it misses the small ring and gets wedged between the inside of crank and bottom bracket.

    Or is it chain suck - that usually means it does not release from the front big ring when shifting to small. It wraps around the back of the big ring, and the chain comes up and gets stuck on the outside of the right frame chain stay. Usually you will see scrapes on the outside of the chain stay 1/2 back with bad chain suck.
    Or are you having both problems?
    I had chain suck on a new bike, it was always going from big front to small, usually also always at big in the rear.

  14. #14
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    Thanks everyone for the responses. Sorry for the delay in getting back to you all.

    Are you sure the limit screws are set correctly? Yes, I know the bike shop says they adjusted them, but they from my own experience, they usually adjust those wider than necessary.


    I believe that's what one of the bike shops did initially until I started doing it myself. I'm fairly confident they are correct or very close since -
    but I'll readily admit I could be wrong.

    I have the SRAM force yaw derailleur and started with following the SRAM install instructions. Then I found a GCN video which really simplified the installation/adjustment. It relies heavily on the limit screws to get the yaw set properly.
    Now I'm cringing waiting on cxwrench to blast me...

    It seems as if my derailleur with the yaw adjustment gets a little out of whack over time - could be from the wrenching it takes when it drops and yanks the chain past/through the catcher. I usually take it back to square one and re-adjust it every 6 months or so just incase.

    Or are you having both problems?
    I had chain suck on a new bike, it was always going from big front to small, usually also always at big in the rear.


    Both. Exactly the situation I am seeing.


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