[Bubba74]

I recently went to a 24-36 2-ring setup with a new chain, new rear cassette, and new rear derailleur. The middle ring is an FSA CNC'd black anodized ring. When I am in granny and usually 2 to 4 gears down from the 34T cog I get chain suck usually when I'm going over very rough terrain (rear suspension being active). This does not happen when I'm on smooth ground, nor did it happen on the old drivetrain. I usually have to back pedal 1 or 2 revolutions to clear the problem and then I'm fine.

Any ideas?

BTW the chain has been thoroughly degreased and I lube it once a week or so.

 

[jyeager]

Chain suck? I thought chain suck was when it jumped between the top cog and the spokes. But you say it's not when you are on the 36, but rather a few down. So where is it being sucked?

Do you just mean it's jumping off the granny gear in the front?

 

[Bubba74]

Chain suck is when the chain does not release off of one of the front chainrings and starts to follow up and usually bind up the chain and scratch the chainstay. The granny chainring is usually the culprit. Chain suck doesn't occur on the rear cassette.

 

[b4 stealth]

Chain suck is where the chain doesn't release from the teeth on the front chain ring, but gets carried up and thus jammed in between the chainring and the chainstay. I don't know why this is happening, or have a fix , just clarifying for the above poster.

EDIT: grrrr... beat me to it

 

[Bubba74]

EDIT: grrrr... beat me to it

hehe, sry

BTW, I do know that the chain isn't binding with my frame. I have a C-dale prophet, so the elevated chainstay doesn't get in the way.

 

[4slomo]

Is your new chain the correct length for your new 2-ring drivetrain?

 

[Bubba74]

Is your new chain the correct length for your new 2-ring drivetrain?

Yep, big-big +2 links

 

[littlejohn]

have you check your chainline??

 

[Bubba74]

no different than it was before. In fact on smooth ground, I can run granny and the 13T or the 15T without problems (even though I don't normally run that ratio).

 

[piranhajon]

I'm having the same problem on my GT Zascar (hardtail). I just got a new chain and I measured it on the same way: Big chain ring in front and big cog in back plus a link (2 sections of a chain). It only sucks when I'm pedaling hard up hill, of course. After reading this link that has more than you would ever need to know about chain suck............
http://fagan.co.za/Bikes/Csuck/ there is no doubt that I need to replace my smallest chain ring in the front. At first I thought it could have been a bent rear derailleur hanger, but this link explains it all.

 

[Ericmopar]

The granny was not listed as a new part that was installed, so my first question is, is the the granny ring old or new?
If it's old, it's probably "hooked" and the new chain is catching on the worn teeth.
If it's new, then my next question will be. Did you install a Sram chain?
I've had so many drivetrain issues since Sram came out with their 900 series chains, that I finally went back to an all Shimano drivetrain after using Sram chains and cassettes for over two years.
I no longer have any chain suck, bent cassette teeth or other problems.
I just checked my chain the other day, and found I'm getting much less wear than before.
With all Shimano parts, my driveline is less sensitive to mixing old and new parts together as well.
I don't know what happened to Sram, but with the exception of their X.0 and X.9 dérailleurs, they don't have much to offer these days.
Since Shimano came out with their Shadow dérailleurs, the X.0 and X.9 aren't as appealing anymore.