Chain Suck ???

Discussion in 'Bicycle Mechanics and Repairs' started by Gary D, 3 Oct 2007.

  1. Gary D

    Gary D Well-Known Member

    What is Chain Suck?

    What are the causes and effects?

  2. col

    col Veteran

    I think its the turm used when the chain bounces up on the lower part and hits or jams in the frame between chainwheel and frame?
  3. summerdays

    summerdays Cycling in the sun Moderator

    Don't know why but my bike has suffered from this from shortly after I bought it last August. They changed the front rings at the free service, and it still occasionally does it... but I know the noise/sensation and stop before it gets well and truely jammed up now. However after it has done it it then makes me very cautious going up hills (which is when it seems to happen to me), and the LBS say its something to do with my technique when changing gear when cycling up-hill, that I put too much pressure on (how else am I meant to get up the hills in Bristol), and that I should kind of stop pedaling a bit as I change down.

    Its a horrible sensation as the bike literally lurches to a stop immediately. One time it took my hubby and a passing cyclist about 10 mins to free the chain from between the rings and frame.
  4. col

    col Veteran

    This doesnt seem to be chain suck,is the chain coming off when you change gear and jamming on the top of the crank inside the chainring?
  5. summerdays

    summerdays Cycling in the sun Moderator

    No the bottom part of the chain comes up instead of heading for the rear wheel, and becomes trapped between the rings and the horizontal bar going to the back wheel (I know very technical terms I have used), the chain is not off either the front or the reach mechanisms, just pulled up into a place it should not be in... Is that chain suck?
  6. found this here

    The chain fails to disengage from the bottom teeth of a front chain-ring ; instead the teeth snag the chain and carry it up and around the rear circumference of the ring, winding it back onto itself, and jamming it between the chain-rings and chain-stay.

    Because it usually occurs unexpectedly during forceful pedalling, the chain can be permanently twisted, teeth can be damaged, and chain-stays of aluminium or carbon-fibre can also be damaged by the chain being wedged hard against them.

    It occurs most frequently with small chain-rings (granny-rings) of triple-ring MOUNTAIN BIKES, but does also occur with larger rings, and on ROAD BIKES. There are two main forms of chain suck :
    1-ring suck : the chain is snagged by teeth on a single ring during normal
    pedalling (usually the granny-ring)

    2-ring suck : the chain snags on teeth across two rings when changing
    gears (usually from the middle ring to the granny)

    the link goes into more detail.
  7. summerdays

    summerdays Cycling in the sun Moderator

    Thats right ... that is what happens to me when I am going up-hill and usually when changing from the middle to the granny ring.
  8. col

    col Veteran

    If your on a smooth road while this happens,it shouldnt really?I believe its the bouncing of the bike on the rough that can encourage this,there are gizmo's for mountain bikes to stop this happening,but on the road?Im wondering if the set up isnt entirely right,if its a regular occurance?
  9. summerdays

    summerdays Cycling in the sun Moderator

    Mines a Dawes Saratoga - not sure if it would be the bike I would of bought now if I was buying again, but it gets me around the different parts of Bristol I need to commute to. Its a couple of months since I had one of those nearly moments... perhaps I don't lubricate it enough - although considering how black my trouser bottoms always get I don't see how. I will have to look at the chain the next time it does happen to see if its dirt/lubrication related.

    I have had to commute up the Muller Road recently, my most hated hill in Bristol and I haven't had the problem - probably too worn out to put too much pressure on the pedals. The only hill where I love Red traffic lights cos I can catch my breath and rest my legs.
  10. Arch

    Arch Married to Night Train

    Salford, UK
    If the chain is failing to disengage properly, it might be worth checking a) that the chain isn't too long (and therefore loose) and ;) that it (and the teeth of the chainwheels) aren't too dirty and clogged with oil and dust or maybe c) that the rear derailleur is keeping enough tension on the chain when you change. Oh, and d) that you don't have any 'sticky links' - parts of the chain that don't swivel on each other so freely - this can be due to rust, too much crud, or an overtight pin joining the links... Rotate the pedals, and check the parts of the chain you can reach to see if it is freely bendy... (Does that make sense?)

    Extra lubrication may not be the thing to do without cleaning the bits first. Excess oil tends to pick up dust from the road and become sticky, which might cause the problem.

    It is a good idea not to be changing gear under maximum strain - if necessary change your style a little in order to change down a little earlier and spin for a bit longer, so that you aren't straining too badly when you do change.
  11. OP
    Gary D

    Gary D Well-Known Member

    Thanks everyone for the replies. Especially pw91 for the helpful link.

    I asked the question because my wife has experienced a couple of "chain off" moments during the last 2 rides she has done. Interestingly, also on a Dawes (Discovery) but probably coincidence. Trying to get her to describe exactly how/what circumstances it occurred is difficult - but she did say it happened when on the granny ring.

    However, after reading the article, I think it was most probably caused by a dirty chain and chainrings also in need of lubrication. Although they aren't really bad, I think it is enough to cause the problem.

  12. Tynan

    Tynan Veteran

    unless you're some sort of maniac freak this sounds unacceptable on a new bike to me
  13. yenrod

    yenrod Guest

    Cause and Effect...Ive been riding my bike since new from April I think and had a tad of this once...

    I feel to stay on top of this you've got to, clean between EVERY tooth, clean the chain, clean the sprockets, time consuming yeah; but worth it esp. if a fair distance away from home...

    Gonna have to sort a big clean of my bike even thoght not encrusted with crap..its best to keep it pretty good rather than pretty ok,....

    Though, to put it straight its quite 'heavy' to think you'd have to replace the rings AND block AND chain when every so often; the question is...

    Ive always thought that the C.Rings are quite durable...thoough what comes to mind is narrow chains !

    Remeber when shimano 1st started narrowing the chains on the 7sp. stuff and they got narrower and what they are now: to fit 10sp. Pretty obvious really ????????????

    Add in road dirt and stick 'old' lube and....
  14. woohoo

    woohoo Veteran

    I've had the chain jam between the small chainwheel and the frame on both my MTB and my road bike (when they were both new). On the MTB, the problem appeared to be the chain tension and I removed a link which solved the problem. On the road bike, which has a 34/50 compact chainset, the front changer was shifting too far inward with the chain was coming off and catching the inside of the small chainwheel. It took ages to get the adjustment right on that one.
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