Chain Suck

[caleb]

I've been having some trouble with chain suck.

The crank is a Chorus UT CT 50/34, the chain is Chorus 10, and the cassette is Centaur 11-25.

I occationally have a problem when I dump the front ring and downshift in the rear.

I know shifting more smoothly is an answer, but it's not an answer I like. I want to race this bike next summer, so it can't blink.

Moreover, I can do this same sort of shift on a Shimano 9 setup with a Ritchey or Shimano compact crank.

Any thoughts?

[swoop]

are you well lubed? how is your chain line?

[caleb]

Lube: Always :beer:

Chainline: I haven't checked. But I can't adjust it anyway, can I?

[swoop]

did you try a different back wheel?

[Kevan]

existing wax lube? Remove it and relube.

Too much chain, too many links?

[Samster]

your chain must suck.

<sorry.>

[navclbiker]

Hey there. I'm new to biking jargon. Please tell me what chain suck is. I may have experienced this just a few days ago.
-Dave

[swoop]

do a google search "chain suck". i'm too lazy to type and the things that come up are spot on!

[caleb]

Two different wheels - same issue.

Chain is about as short as it can be.

Went from a long cage derailleur to a short cage.

Tried a couple of different lubes.

So, I've tried about everything there is to try.

Should I try a new chain?

[thwart]

Well... is the thing called a dog fang? Anyway, you mount this on your seat tube near the small chainring and it prevents chain drop episodes... popular in 'Cross from what I hear.

If you've tried everything else...

But BTW, what type of FD?

[Richard]

Ususally caused by a munged up tooth. Either a rock hit or a full power shift tweaked a tooth on the chainwheel and it doesn't quite release. Inspect them very carefully. Try new ones.

[93LegendTG]

Dropping a chain during a shift and chain suck are two completely different things. If you're talking about dropping your chain down to the BB as a result of an overshift, the Deda Dog Fang is a product that will solve your problem. I use them on my cross bike and road bikes with compact cranks.

[csm]

if it's a dropped chain, it should be an easy enough fix.

[gdw]

Check out this site:
http://www.fagan.co.za/Bikes/Csuck/

Make sure to keep your drivetrain clean as well as lubed and practice smooth shifting. The 16 tooth difference between the two rings creates quite a bit of slack in the chain especially if you're also shifting to a smaller cog. The rear derailleur is really being pushed to it's limits and isn't taking up the tension in the chain instantaneously. The slack chain can bounce up and catch in the teeth, facing the rear of the bike, of the smaller chainring and be "sucked" back into itself and jam the drivetrain.

[caleb]

Okay, so I think the next step is to reduce the distance between the rings and get a new outer chainring to make sure all the teeth are good.

Problem is, these rings are proprietary.

Anyone know if these Stronglight rings are compatible?

http://www.xxcycle.com/110-compact-ct2-special-campagnolo-1,,en.php

[regularguy412]

Check out this site:
http://www.fagan.co.za/Bikes/Csuck/

Make sure to keep your drivetrain clean as well as lubed and practice smooth shifting. The 16 tooth difference between the two rings creates quite a bit of slack in the chain especially if you're also shifting to a smaller cog. The rear derailleur is really being pushed to it's limits and isn't taking up the tension in the chain instantaneously. The slack chain can bounce up and catch in the teeth, facing the rear of the bike, of the smaller chainring and be "sucked" back into itself and jam the drivetrain.

I agree with gdw on this one. The rear der. only has just 'so' much spring tension available. Changing both ders at the same time while going over rough pavement and/or heeled over in a turn is asking quite a lot -- even with today's better-shifting systems. My suggestion would be to first shift _UP_ to the harder gear with whichever der you need to do that and then shift the other der _DOWN_ to accomplish the complete double shift. Allow a second or two in between the two shifts. Generally, an experienced racer will be able to anticipate the next gear change and accomodate the ders. If done properly, the one or two second delay in getting the gears changed won't negatively affect your performance or race outcome. This is also easier on equipment, since while racing you're already thrashing the bike around anyway. If you break it, you're performance suffers most. A wise person once said: "To finish first, one must first finish".

Mike in AR

[Dave]

Okay, so I think the next step is to reduce the distance between the rings and get a new outer chainring to make sure all the teeth are good.

Problem is, these rings are proprietary.

Anyone know if these Stronglight rings are compatible?

http://www.xxcycle.com/110-compact-ct2-special-campagnolo-1,,en.php

How did you come to that conclusion? Big ring chain suck would be rare and even more rare with a relatively new UT crank. Reducing the distance between the rings is not practical, nor should it be necessary. I suppose you could have a defective ring or hit it on something, bending a tooth.

There's no off-brand of ring that will shift any better than a Campy ring. Chainrings for the Record and Chorus cranks have one bolt hole that is either 112 or 113mm instead of the normal 110mm. Both Stronglight and TA make compatible rings. The link you've posted says the rings are Campy compatible.

Are you sure you know how to adjust the chain length? It should be set, so it's as LONG as possible, in the little ring and smallest cog. If it's too long, then the chain will either hang loose or rub on the RD's upper pulley chain guide tab. Remove 1 inch at a time until you get the maximum length.

You could also have a RD problem, where the cage is not moving freely with proper spring tension.

[caleb]

How did you come to that conclusion? Big ring chain suck would be rare and even more rare with a relatively new UT crank. Reducing the distance between the rings is not practical, nor should it be necessary. I suppose you could have a defective ring or hit it on something, bending a tooth.

There's no off-brand of ring that will shift any better than a Campy ring. Chainrings for the Record and Chorus cranks have one bolt hole that is either 112 or 113mm instead of the normal 110mm. Both Stronglight and TA make compatible rings. The link you've posted says the rings are Campy compatible.

Are you sure you know how to adjust the chain length? It should be set, so it's as LONG as possible, in the little ring and smallest cog. If it's too long, then the chain will either hang loose or rub on the RD's upper pulley chain guide tab. Remove 1 inch at a time until you get the maximum length.

You could also have a RD problem, where the cage is not moving freely with proper spring tension.

Basically I've done everything else - chain and derailleur. The only thing left are the rings. I'm guessing I got a bad ring. I bought the crank new on eBay from a guy who was blowing out a bunch of new stuff, and I'm guessing I got a chainring that didn't make it through quality control.

I ordered the Stronglight rings in 48/36 for two reasons:

First, it's the gearing I want. Unless you ride in the mountains or are a terrible climber/overweight there's no reason for a 16 tooth gap on a crankset. And, if you spin at about 90rpms and tend to ride 18-22 mph (like many, many cyclists do), you spend lots of time cross chained. I like having a smaller big ring because I can't sprint at 40+mph, but I don't need gearing to climb the Galiber either. 48/36 with an 11-25 gets me there.

Second, that 16 tooth gap gives the chain lots of reason to bounce when downshifting. Less gap should make for smoother, quicker shifting between the rings, at least in my estimation.