Bicycle Mechanics - Rubbing while in middle chain-ring
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I understand that if you are in a gear that is cross-chaining, you can expect some amount of rubbing. However, when I'm in the middle chain-ring, the chain seems to be rubbing on the inside of the front derailleur on the largest 2-3 cogs (on an 8-speed cassette). This isn't normal is it? I don't know much about bicycle maintenance beyond a simple flat-repair and basic cleaning/lubing, so if you guys have any suggestions (worded for a complete newbie to this), I'd greatly appreciate it. Beyond being annoying (since I'm in the middle ring and largest 5 or so cogs most of the time - it's pretty flat where I ride), I can't imagine it's very good for the chain or derailleur.
Let me know if more information is needed. Thanks in advance.
06-26-07, 03:28 AM
Back the cable tension off just a bit with the barrel adjusters. Screw them in to decrease tension and out to increase it. Make small adjustments and be sure to count them so you can go back if things get worse. If that doesn't help it may be that you need to do a full alignment with limit screws and cable tension, but if you're no having trouble shifting from chainring to chainring I think cable adjustments will work.
06-26-07, 04:54 AM
If that doesn't work then find a good LBS mechanic to properly adjust the FD position. I end up adjusting a lot of derailluers for friends where the alignment and height above the large chain ring is too much. The first thing to do is what the first answer says.
Ok, I'll try the cable adjustment first, thanks for the suggestion. And no, I don't seem to be having any trouble shifting.
What kind of shifters do you have? A lot of them actually have two positions or "clicks" for the middle ring so that you can "trim" your front derailleur to stop the scraping. Even my wife's low-end Trek Navigator has a couple of intermediate positions between the "1" and "2" front rings that are helpful for this condition.
I have Shimano Sora STI. I think I read somewhere that you cannot trim a triple with the Sora's :(
Right -- that's one reason why I swapped my Soras for ST-R500s that do have the trimming feature. With the standard Sora you might just have to accept that it will rub at one extreme or the other, but then there are always other gear combos using the inner or outer ring that are equivalent to the middle ring with the larger or smaller cogs. So you just might have to shift rings more often. ;)
Yeah, I'll definately shy away from Sora's in the future, but this is my first road bike and I wanted to make sure I stuck with it before spending a ton of money.
Also, I definately accept (and expect) rubbing in the extremes, but on a triple, I would think the middle ring and the first 3 large cogs would not be cross-chained and should not cause rubbing like if I was in the small ring to small cog or large ring to large cog.
Anyways, I'll start with the minor adjustment suggested earlier when I get home...
Ok, I backed the tension off the cable a bit as suggested, and it seems that if I loosen it up enough to where the chain stops rubbing, then when I go to shift, going from the middle ring to smallest works, but it won't go back from the small ring to the middle ring. I increased the tension enough so that the shift worked, but then it was back to rubbing :-/
Anything else I can try? I don't mind taking it in to the shop and supporting my local wrench, but I was hoping to learn how to do some of these seemingly routine adjustments myself...
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