Drive chain problem
 

I'm having problems with:

DRIVETRAIN:
Shimano 105, 30-speed Shifters and Derailleurs
FSA Vero 3-Piece Aluminum Crankset with 50/39/30T CNC 7075/T6 Aluminum Chainrings

and am pretty much a noob at this. I'm sure the bike shop will fix it for me, but I'd really like to become more self-reliant.

The middle gear of the front gearset is losing the chain every rotation. The chain isn't hitting the derailer at all... it's just that every cycle of the gear the chain loses its seating and starts riding on top of the teeth rather than set down between them. This causes one of two things to happen... either the chain clicks back into place with a small jerk, or the petals simply spin under the chain causing a grinding sound and difficulty pedalling. It seems to be worse when the rear gear is set to the middle gears rather than the very large or very small.... pretty much right when you should be using that gear. The larger and smaller front gear are not having this problem.

Any hints before I take it to the shop?

Check the cable tension. It may be too slack.

The cable to the front derailer? It's not the derailer hitting the chain... it's just the chain slipping off the gear. Again... I've had my bike about a month... so all this stuff is pretty new to me.

Further info... one of the teeth in the middle gear is noticably bent in towards the smaller gear... probably a 15 degree bend. The chain will not go on this tooth, but rides on top of it. Is that normal?

The derailleur moves the chain to set points - over the chainring. There are stops that limit the inner and outer movement and those are set with screw adjustment. Cables stretch from use, usually when new. That tends to have the largest impact on the middle chainring of a triple set up. You can check it out and make adjustmenst per here:

http://www.parktool.com/repair/readhowto.asp?id=75

Some of the teeth will have special shapes to enhance shifting, but if you have only one "bent" tooth you may well have a defective chainring. It may be better to have it replaced rather than trying to straighten it. This does not sound like a derailleur adjustment problem to me.

Al

I have had this same problem on my Giant OCR2 TWICE :eek:, which uses this exact same FSA setup you describe. After the first time, it was replaced with a brand new middle ring of the same type. (Both times , I was in the middle of 200K brevet which made it a lot more interesting to finish with only two working rings... :notamused: )

The fact that it happened twice makes me believe that there is some kind of design problem with the setup in general. After the second time, I got my LBS to put on a Shimano crankset and rings, and they managed to get it warrantied through Giant. I have about 450 miles on this setup with no signs of trouble.

(Side Note: The new Shimano is 52-42-30, which seems to require a lot less shifting in the front rings then the original 50-39-30 setup did)

The tooth on the gear was straightened out and the gear now holds the chain. I'm hoping the gear wasn't weakened, but for a free repair it seemed to hold up pretty well.