Dakar XC rear derailluer issue

[Jamis-XLT]

On our way to one of our far away trails in Miami, Oleta park. We stopped at a LBS to pick up a helmet for my daughter. We walked by a white 2008 Jamis Dakar XC 17 inch and my daughter instantly fell in love with it. The dealer worked out a great deal for the bike and helmet, tuned the bike and off we were to the trails. As we hit the first trail, I heard some banging noise coming from her bike. It turned out that the rear Deore derailleur was banging against the bottom of the swing arm. I fiddled with it and then shifted it to the big ring up front, which helped a little. I noticed the paint was chipping where the derailleur had smack the swing arm, so we called it very short day.

I returned to the bike shop where I bought the bike and we compared it to another bike of the same size and model. Both had the same issue. The dealer worked on it for about an hour, replacing the shifter cable and then put a longer chain on. This seemed to have resolved the problem, but the chain seems to be a bit too long when in both small rings. I later compared this with my wife's 2006 Dakar XC and her Deore derailleur seems to have a stop built in to prevent it from this. My XLT 3.0 has an XTR derailleur on it so I really can't compare it to that one.

Is this common out there with the newer Jamis bikes? Can any other (closer) Jamis dealer work on this? I kinda pissed that my daughter thinking her old Schwinn S-40 is a better built bike then her new one.

[MartinsMental]

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[debusama]

I have a 08 19” Dakar XC, and I had the same problem. I Temporarily zip-tied a piece of tire tube to the chain stay so that it won’t chip the paint, and it does quiet down the knocking. I’ve also been asking around about this problem, and people seems to think a little bit of rattling is no normal, but I don’t think they would say that if they heard it… It really knocks hard! The shifting in the rear is pretty crunchy; particularly under load (the chain has fallen off on me a few times while climbing and down-shifting) the drive train seems to be a week link on this bike. That KMC chain is notoriously bad, the rear cassette is cheap and heavy, and that derailleur really swings around a lot. I noticed that I could make it knock just by lifting the rear of the bike by the seat and shaking it a little. I was going to get a new cassette, chain and derailleur anyway. I love the bike, but I don’t think the Jamis people were thinking too much when they decided to match that particular derailleur with this bike. The combination of the low sweeping chain stay and the floppy derailleur just isn’t a winner.

I bought the bike because I had ridden a Dakar before and I really loved the way it handled and how there wasn’t any noticeable bob when I stand and hammer up a hill. I had already planned on replacing a lot of the components, but at least I could ride and train on the ones that came with the bike while I save up the cash. Only having paid $650 for the bike, I knew I’d have to spend another 500 to get the weight down, and to make it ride the way I want. Even still, it isn’t as if I could have gotten a better full suspension cross-country bike for $1150. It is a bummer though, to have and issue do deal with on a brand new bike.

[ATBScott]

Sounds to me like the "B" adjustment screw is not screwed in far enough, and that the chain is likely too LONG More tension on the chain will tend to pull the rear derailleur's jockey roller down, and away from the frame (bottom of the chainstay) and it will also move away from the frame as you shift to a larger rear cog. Specialized with the Horst link will tend to do this - my bike came with the rubber bumper that the Big S shipped with the Enduros years ago - but some careful adjusting of chain length has not had it hitting. A friend of mine has a Dakar, and has no problems with this - so likely it is just a set-up issue.

[Hip]

I have an 08' Komodo 2 with the same problem. I wrapped black tape around the frame and it beat right through it.