Noob question of the week: what's the deal with chain suck?

[Tom Goodmann]

So, my naive question this week is: why do so many frames bear the scars of chain suck?  I make no boasts about my own riding, none at all, in terms of distance, longevity, or rigor. but I can't think of more than a couple of times I've ever thrown a chain.  What causes the chain suck?  Over-shifting? (missing a gear or two or three)  Shifting hard on a climb?  Is this an issue that has gone away for those riding with indexed shifting, and so more of an issue with friction-shifters?  Really just wondering.  If this question is too dumb for words, you can reply off-line: tgoodmann-at-gmail, etc.

[Jim Thill - Hiawatha Cyclery]

Chain suck is primarily caused by a combination of chain/chainring wear, filth, and lack of finesse in one's shifting technique.

[PATRICK MOORE]

Not a dumb question at all. I just came across this:

http://fagan.co.za/Bikes/Csuck/

Haven't read it, but it's a Sheldon referral, so likely to be good. (I
plan to read it myself.)

The general reason is that the chain does not disengage from the
bottom of the inner chainring; thus the chain gets pulled up and
(don't know the reason for *this part*) and also moves inward and
jammed between ring and stay. But being pulled up on the bottom of the
inner ring is one of the general conditions.
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Patrick Moore, Ph.D, MBA, ACRW, Albuquerque, NM, USA
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[dougP]

Tom:

My experiences with chain suck have occurred when shifting between the middle & inner chainring.  When it happens, the chain is mostly on the inner ring BUT some of it has gotten "sucked" between the middle ring & chainstay, resulting in paint removal at the least & much tugging & cursing at the worst.  Jim has suggested specific conditions, and I concur with the technique issue.  Mine almost always happen when faced with an unexpected need for granny over middle, such as rounding a corner & seeing an "oh crap" grade change, and just flopping the shift lever & hoping for the best.  Wear, lubrication, maintenance, are also possible culprits but I'll lay most of my experiences to simply being clumsy.  Covers a lot of other sins as well. 

There was a recent thread discussing chain ring spacing that got me to looking at my set-up & there is visually more space between my middle & inner than middle & outer.  I intend to pursue this question but getting around to actually measuring & figuring out some spacers, etc., is a project for "one of these days". 

The quick fix is a bottle of touch up paint. 

dougP

[Deacon Patrick]

Until today, the only chain suck I've had was user ineptitude. But I managed to gunk up my chain rings on a gloriously sloppy ride and they too a few miles to self-clean (the primary means my Hunqa has of getting clean).

With abandon,

Patrick

[Steve Palincsar]

On Thu, 2013-03-07 at 19:24 -0800, Deacon Patrick wrote:
> Until today, the only chain suck I've had was user ineptitude. But I
> managed to gunk up my chain rings on a gloriously sloppy ride and they
> too a few miles to self-clean (the primary means my Hunqa has of
> getting clean).

A friend of mine had a serious chain suck problem on a road bike that
turned out to be a bent tooth on the chain ring. She must have hit the
ring on a concrete step getting down into the basement.

[Garth]

I've been riding triples since the early 80's ... never once have I experienced "chain suck" .   I keep my FD perfectly tuned however, and I guess I must have good enough technique to not to have experienced it ;) 

[Joe Bernard]

Bad chainrings, bad derailer adjustment, bad shifting technique, bad karma...the causes are endless, but they all lead back to one common denominator: Triple cranks. I'm so tired of the issue that I eschewed triples and front derailers altogether, and put a 2-speed FSA Patterson Transmission crank on my Saluki. No more moving the chain around, no more chain suck.

 

Joe Bernard

Vallejo, CA.

[Shoji Takahashi]

There are devices to protect against chain suck. Essentially, they block the chain from coming up with the chain ring. RR36 has a few pics of commercially available devices (don't know if they're still around) and a homemade zip-tie version. Seems like some cranks/chain ring combos are more prone to chain suck than others. 

[PATRICK MOORE]

I had one of these -- forget maker -- installed by a LBS after the
last disastrous (bent not only chainring but chain!) suck event.
$14.99 full retail, IIRC. Should have installed one the first time
suck happened.

I've made ad hoc suck prevention devices out of hose clamps
strategically placed; the end of the tightening bolt, placed close to
the small ring, kept the chain from being sucked up.

__________________________________________________________________________

BUSINESS BUILDING COME-ON!!
$300 off a $600 resume + letter or Linked In profile package with
referral that leads to full price sale! Refer two full-pay clients and
you get the package for free!

I am not cheap, but I am very good. So they say.

Patrick Moore, Ph.D, MBA, ACRW, Albuquerque, NM, USA
http://resumespecialties.com/index.html * patric...@resumespecialties.com
__________________________________________________________________________

[Cyclofiend Jim]

A lot of times, you can flip the ring and remount - watch for bolt heads contacting the frame if one side has recesses for the bolts.

- J

[Cyclofiend Jim]

Hmmm... downhill with low-load and brand new components is definitely weird.  I'd suspect a stiff chain link before blaming an inherent design flaw.

(And just to restate it, we're talking about chainsuck with the chain not letting go of the chainring from the 6 o'clock position, and climbing up into the chainstay from below.  Not simply jumping off the ring during a shift.)

On the other hand, it may have something to do with where the bottom bracket is with respect to the shifty bits...

Most mtb's have reasonably high bottom brackets - certainly when compared to the RBW designs.  And Grant's bikes have lengthy chainstays.  Combine that with wide range gearing and you probably end up with a bit more slack and less tension in the drivetrain.  So, you are coming from a "lower" point, which could wrap an extra tooth or two.  With no chain tension drawing the chain towards the derailleur, you start wrapping things up.  It's less than a 1/4 turn of the cranks, so it can happen fast.

Any "sharkfinning" on the chainring would of course exacerbate that.

Pure, unadulterated conjecture on my part.

- Jim / cyclofiend.com

On Sunday, March 10, 2013 11:54:11 PM UTC-7, samh wrote:

>I guess I must have good enough technique to not to have experienced it ;)<

I really don't think it has anything to do with shifting technique.  I have triple's on mountain bikes that get muddy, and I've never experienced chain suck while riding them. Sometimes my mountain bikes are sporting worn chainrings, cog sets, or chains.  Sometimes those components are new.  I have doubles on my other road bikes, and they've never experienced chain suck.  

I've switched gears in every conceivable situation, high load, low load, wrong direction, right direction, while double shifting, or single shifting--no chain suck ever.  I've snapped chains while mountain biking due to bad shift choices, but I've never experienced chain suck.  However, while riding my Rivendell on its maiden voyage, I experienced chain suck during a low load shift while riding downhill.  Based on all the damaged chain stays I see in pictures of used Rivendells, it appears to be a common problem.

That's been my experience.  I'd welcome a commercially available device to prevent chain suck on my Rivendell.  Perhaps they should be standard equipment?

On Friday, March 8, 2013 8:05:20 AM UTC-7, Garth wrote:

I've been riding triples since the early 80's ... never once have I experienced "chain suck" .   I keep my FD perfectly tuned however, and I guess I must have good enough technique to not to have experienced it ;)  

[Tom Goodmann]

Your conjecture makes a lot of sense to me, Jim: chain slack might be the leading element, suggesting careful maintenance in that regard.  I'm new to Rivendells, and as I check out frames for sale, I can't help but notice the frequency of scarring to the drive-side stay, so I asked.

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[Shoji Takahashi]

Thanks, Jim, RE: conjecture. Does chain suck happen more often with certain types of derailers? I would guess that ones with weaker chain-tensioner springs would chain suck more often. (Perhaps something w/long cage vs short cage given the chain angle.) Seems like the chain-suck descriptions I'm familiar with (=not many) don't mention the rear derailer used. 

Then again, this is probably starting to over think the situation, and I need to go out and ride more. :)

[dougP]

Another consideration may be chain length.  Sheldon has a procedure for optimizing chain length.  I followed it a time or two but it only required taking out a link or 2, so I went back to just installing them as-is out of the packaging.  Thinking back on it, I can't recall a chain suck event with the chain properly lubricated, and when it did happen the chain was always really dry & I couldn't recall its last lube session.  I'm going with lubrication as the culprit.

dougP

[Jude]

On Mar 11, 2:31 pm, Cyclofiend Jim <cyclofi...@earthlink.net> wrote:
> Hmmm... downhill with low-load and brand new components is definitely
> weird.  I'd suspect a stiff chain link before blaming an inherent design
> flaw.

Count me as another user who experienced this. Maiden voyage of my
Atlantis. Very easy riding, just checking out the gears, flat ground,
zero load, normal shift into the granny ... CRUNCH!!!

Everything was new and built up by Rivendell. One additional data
point. It was darn cold that day (which I've heard can be a
contributing factor).

Chain suck has happened to me maybe a dozen times in the five years
since. I could install an anti-suck device but the damage has been
done (over and over). I just stomp the chain out (cringe) and keep
riding. Once, it was so bad I had to pull the crank (that was ugly,
extra hard stomps didn't work) luckily I was close to home.

I can usually avoid the problem with an extra careful shift. But when
I'm tired and forget to be gentle ... CRUNCH!! I think it's probably
a combination of Triple / small granny / shaped chainstays.

-Jude

[PATRICK MOORE]

Be careful with this method. I've done that and ended up with a
severely bent chainring and permanently deformed (twisted) chain, not
to mention new gouges on the chainstay. I finally installed a
preventer device.

On Wed, Mar 13, 2013 at 9:24 AM, Jude <jei...@gmail.com> wrote:
>
> On Mar 11, 2:31 pm, Cyclofiend Jim <cyclofi...@earthlink.net> wrote:
> I could install an anti-suck device but the damage has been
> done (over and over). I just stomp the chain out (cringe) and keep
> riding. Once, it was so bad I had to pull the crank (that was ugly,
> extra hard stomps didn't work) luckily I was close to home.

--

[Garth]

On Monday, March 11, 2013 4:41:22 PM UTC-4, Shoji Takahashi wrote:

Thanks, Jim, RE: conjecture. Does chain suck happen more often with certain types of derailers? I would guess that ones with weaker chain-tensioner springs would chain suck more often. (Perhaps something w/long cage vs short cage given the chain angle.) Seems like the chain-suck descriptions I'm familiar with (=not many) don't mention the rear derailer used. 

Then again, this is probably starting to over think the situation, and I need to go out and ride more. :)

 That may be part of it, as well as "monkey see problem in another, monkey start to have problem".  The springs in modern derailers are weak compared to those from even the 7,8 speed ones.  I have a Shimano LX rear 9sp. that flops the chain all over the place with bumps, but an XT 8 speed and older Shimano from the 80's do not.

That said, I still have not experienced , ever ... lol. 

[William]

Chainsuck definitely is a huge bummer.  It would be an even more huge a bummer to have it happen on a brand new bike.  Like Garth, I'm grateful to have never had a bad instance of it.  As a shop mechanic, I've seen it plenty.  If somebody challenged me to force it to happen on a brand new bike, I wouldn't bet a lot of money that I could force it to happen.  If I had to make a chainsuck happen to save my life, and I only had one shot at it, I would shift from big ring to middle ring in front, one of the smaller cogs in back, under heavy load.

[Cyclofiend]

On Mar 13, 2013, at 10:22 AM, Garth wrote:

 That may be part of it, as well as "monkey see problem in another, monkey start to have problem".  The springs in modern derailers are weak compared to those from even the 7,8 speed ones.  I have a Shimano LX rear 9sp. that flops the chain all over the place with bumps, but an XT 8 speed and older Shimano from the 80's do not.

Yep.  Those of us who suffered through the "bassworms" and other return spring tension solutions in trying to use SRAM mtb shifters with Shimano rear derailleurs know that the later seriously lightened the spring tension throughout their designs in the 90's.