I have a Sugar 2+ disc and I have a chain issue that won't go away.
The the bike has less than 1000 total miles. I replaced the chain last year cause I kept getting chain suck and finally bent the chain so bad it wouldn't spin without skipping.

New chain didn't seem to be working, so I took it to the LBS and they tuned it up and I thought all was well. Well the magic only lasted 2 rides. Last ride on a freeride trail in JH, WY with about 300 total yards of climbing my chain snapped in half while pedaling up a pretty small hill. I couldn't believe it.

My theories
-Possibly worn out bushings in rear end (is this common?)
-Maybe I cracked the rear swingarm and don't know it (I can't see any visible cracks)

I know the chainline on the Sugar's isn't really good, but I take extremely good care of my equipment and didn't have problems the couple of years I owned the bike. I don't really jump (freeride trail was just for fun as others in group had D/H bikes) very much.

I literally have only gone riding a few times in the last two years as I'm sick of having my equipment let me down.

I would take bike to LBS that worked on it, but I moved. (Anyone know a good shop in SLC, UT)

First-- and you may have already-- search the forum archives for posts, there are a bunch posts on this.

Next, official line from Trek/GF:

"Chain suck is very elusive and in some cases impossible to solve.
However, it can be controlled and minimized. Before we can solve chain
suck we must first identify what type(s) of chain suck you're having.
Outlined below are some of the more common causes of chain suck:

1). Shifting the ft. derailleur under heavy loads or while out of the
saddle. What happens here is the chain will wedge itself on to the two
rings so tightly that it won't release from either chain ring. The only
way I know to solve this type of chain suck is by educating the rider,
and explain how and why it's happening. Once you know how or why it
happens you can take steps to adjust your riding style to avoid chain
suck.

2). Dirty or worn out chains, chain rings or derailleurs. Maintenance
and replacing any suspect component.

3). Inadvertent chain slap; this is where the lower horizontal section
of chain will bounce up and down hitting the chain stay. If the chain
slides off the chain stay to the outside it can be caught up by the
chain rings and get sucked up between the chain stay and the chain
rings. The best solution I've found for this type of chain suck is a
simple tip tie. Place the zip tie on the chain stay just behind the
middle and large chain rings. The zip tie knuckle should be positioned
under and to the out side of the chain stay. The zip tie acts as an
anti-chain suck device keeping the chain out of the space between the
chain rings and chain stay.

4). Bent or warped chain rings, a chain ring can get bent for any number
of reasons. Inspect them on a regular basis, and replace them when
necessary.

5). Chain drop or over shifting due to ft. derailleur adjustment and or
maintenance. Chain drop isn't really chain suck but it can be seen as
chain suck because the end result is the same, the chain gets picked up
and jambs between the stay and the crank set.

6). Chain drop or over shifting due to frame alignment. Not really chain
suck but the end result is the same. Your retailer can measure and
evaluate the frame alignment and the solution would be to either align
the frame or have it replaced. A shorter bottom bracket may help but it
not the best solution for the long term.

7). Mixed chain rings; e.g. two different brands of chain rings. Because
each manufactures have their own designs for shifting gates even a small
amount of tooth phase difference can and will cause shifting
difficulties and chain suck. Solution; match the chain rings. "

-------

Some frames (earlier for the most part IIRC) had alignment issues. A dealer should be able to tell if your frame is out of alignment. (Or so I've read)

IMO, the source is probably more related to the chainline issue. Many have solved this issue by changing the BB to achieve a smaller chainline, 50mm to 47.5, I believe. This means you will be using a shorter spindle to move the chainrings closer to the midline of the bike.

I'm about to move mine in, so I can't personally speak on whether it solved it for me. There's obviously a lot of factors that can play into it, so going thru the list that GFbikes provides is a good place to start. Oh, check the chainrings, too. The middle chainring did have a issue, if it's stamped w/ a part # w/ a V3, that has been superceded by a different part #, a V5. This may now be superceded by something else. I'm going to try new rings (non-Bontrager) _and_ changing the chainline, as new rings (LX) didn't totally fix it for me, although that did help a bit.

Shifting technique does have a lot to do with minimizing it, but also didn't totally fix it for me.

I'm probably missing something, but here's a start. It's one of the first topics that I came to the board for, so I hope it helps you out. Good luck.

3). Inadvertent chain slap; this is where the lower horizontal section
of chain will bounce up and down hitting the chain stay. If the chain
slides off the chain stay to the outside it can be caught up by the
chain rings and get sucked up between the chain stay and the chain
rings. The best solution I've found for this type of chain suck is a
simple tip tie. Place the zip tie on the chain stay just behind the
middle and large chain rings. The zip tie knuckle should be positioned
under and to the out side of the chain stay. The zip tie acts as an
anti-chain suck device keeping the chain out of the space between the
chain rings and chain stay.



BRILLIANT! - i'm THERE! thanks!

I see this is a old thread, but I also have a sugar 2+ with the same issues...any update on what has helped or not helped. I am about to swith out to new chain again, and with it this time go with a set of Race Face chainrings and a new cassette.... I feel the majority of my problems are incorrect shifting and bent/wore chainrings but any help would be great....

anyone try the Heim 3guide yet>??

side note: I broke my rear triangle on my sugar 4+

just got it back from Fisher with a CARBON FIBER REAR END!!! YUS!!!

aaron

Where at did it break? Did it break completely apart or did you notice stress cracks before it came completely apart?

Also did the zip tie work?????

it broke @ the bottom of the hole section that runs right behind the BB - i actually had it covered up w/ a piece of tube to prevent slap/suck and it was only when I gave it a good cleaning that I noticed it. It was a close to 1" crack running along this "tube" - I had started to get tire rub on the opposite side and could not figure it out, thought it was my rear wheel bearings...but nope.....crack'd! If I'd really torque on it up hills it would RUB - so for about 5-6 good hard rides it had been broke. Then I got my stinky and kinda shelved the sugar....then went to SELL it.....good thing these warranties, good thing!

I have a sugar 2+. I replaced my cranks w/ XT through-axle cranks. I used some spacers also.. but.. anyway.. havent had chain suck in the last couple years.

something also to check for a chain breaking is a bend in the chain. often if you get chainsuck it bends the chain slightly. That bend can cause the chain to break in places even far from the bend. Examine the chain closely and if you see any bend, replace it. Also.. my personal experience is I have better luck w/ shimano chains than sram as far as breakage.