Chain falls off front derailleur AND rubs?
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I have an unusual problem with my bike. It is a Scattante R660 road bike with full Ultegra 6600 components and a Truvativ Rouleur crankset (53/39 double). When I have the bike on the smallest gear (small chainring on the front, large chainring in the back), the chain rubs against the inside of the front derailleur (FD) cage. However, when I shift from large to small chainring in the FD with the rear derailleur on the smallest setting (largest chainring closest to the bike), the chain overshoots every 2-3 times I shift, even though the chain is rubbing against the FD cage as I mentioned before. What's more is that the low adjustment is as far as it can go, so I can't really adjust the FD any more, even if I wanted to (which I don't, since the chain rubs pretty hard). I took it to my local bike shop, and they said they couldn't do anything about it. Their suggestion was to buy a plastic chain guard like the dog fang. Has anyone else had this problem?
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Answer:
I'm going to try and keep this short. 1st a lot of bikes tend to have the chain come off at times if you have the chain on the largest cog in back before you shift the front down to the 39. The chain line causes this. This shifting pattern you explained is something I don't do and is not common with seasoned riders. Try planning your shifting a little more in advance. Next the rubbing and the fact you can't adjust the shifter any further in is a problem. This could indicate a mis-aligned front shifter cage. Your ft. cage should be aligned with the chain while on a middle cog in back. It's possible you need to adjust this alignment. A 2nd possibility is that your chain rings are aligned too far out-board. That is if you flip you bike over pull the chain off the chain rings and look at them by lining up your eye from behind the middle rear cog. (got that?) Your chain rings should be lined up in the middle of your cassette. If they aren't you have an alignment problem. This could be that the drive side crank arm isn't tight or properly seated on the BB spindle. Or it's even possible your frame is off. If someone put this bike together or replaced a crank or BB, it's possible that the wrong spindle length was used. I hope I was clear in what I said. Did your LBS say why it was happening? Not all shops are alike. Some employ kids with little experience and don't work on high end bikes much. If fact a friend of mine brought his bike in to a high end shop for a new crank and BB install. He supplied the parts. He didn't know had purchased the wrong length spindle. A poor mechanic couldn't figure out the alignment problem. The bike was there 3 days. He went back and talked about it with another mechanic. This other guy spotted the wrong sized spindle in a minute. He had the correct size and just traded my friend his for the one the store supplied. He left 20 minutes later with a good working bike. The moral of the story? Get more than 1 opinion. - I guess I couldn't keep it short.
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Other answers
I have the same problem with my road bike, My advice is find the gears you are most comfortable riding in & dial your gears in to that. I find that I do not use all the gears & they run smoother if I make that kind of adjustment.
m_2x4
Because of M R's thorough response I can keep mine real short. M R is correct on this one, I would try another shop. AT least a different mechanic if the same shop.
McG
I can tell you exactly whats wrong, but you probably are not going to like it especially with Truvativ. This will require a VERY experienced mechanic to complete. The chainline issue is the key. You will need to have a 2.0 or 2.5mm spacer placed between the bottom bracket and the drive side bearing cup. If you are lucky the non-drive cup can be screwed in further to take up the slack. If you are NOT lucky then the bottom bracket will need to be faced on the non-drive side to make a width of 66mm and possibly rethreaded, then everything put back together. This is a FRAME QUALITY issue and should be covered under the frame warranty. If the shop where you bought it balks at the idea I would take the issue up the management ladder until you get satisfaction. The FD spacing between large chainring and cage should be at no more than 1/16" (2mm). EDIT: M R... good catch on the chainline, but new Truvativ doubles only have one spindle length being an integrated BB. Scattante frames are pretttty bad when it comes to this.
bikeworks
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