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Old 12-28-03, 05:42 AM   #1
specialized
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Chain alignment

Specialized epic comp 2004. Problem: on center cog (front) and small cog (rear) the chain catches on the inside of the large front cog causing the chain to lift slightly and make unwanted noise.
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Old 12-28-03, 11:40 AM   #2
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Is your middle chainring 'in line' with the middle of your rear cassette? If you have a 9 speed cassette, the 5th cog should be in line with your middle chainring.
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Old 12-29-03, 12:16 AM   #3
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Chain alignment

The middle of ring 4&5 (counting from small side) is in line with the middle front ring. The bike is fresh out of the box from specialized. Any ideas?
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Old 12-29-03, 12:22 AM   #4
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Originally Posted by specialized
Specialized epic comp 2004. Problem: on center cog (front) and small cog (rear) the chain catches on the inside of the large front cog causing the chain to lift slightly and make unwanted noise.
You probably already checked this one, but are you sure it's not the mis-aligned front deralliur that is rubbing? If not, then possibly your bottom bracket spindle length is too narrow, but I can't imagine that a new bike would have this issue.
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Old 12-29-03, 12:45 AM   #5
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Originally Posted by specialized
Specialized epic comp 2004. Problem: on center cog (front) and small cog (rear) the chain catches on the inside of the large front cog causing the chain to lift slightly and make unwanted noise.
I would first reccomend making sure the chainline on the bike is accurate. is your bb shell width correct for the bb you are using. is the spindle length correct for the arms you are using. is everything tight. if all this is good i would then put some small micro shims in between the spider and the big ring, this will space the big ring a bit further out hopefully eliminating the rub. anothe simpler answer would be to avoid using that gear, it is not an extreme but is close enough to give some rub problems. good luck.
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Old 12-29-03, 08:35 AM   #6
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Quote:
Originally Posted by Mtn Mike
You probably already checked this one, but are you sure it's not the mis-aligned front deralliur that is rubbing? If not, then possibly your bottom bracket spindle length is too narrow, but I can't imagine that a new bike would have this issue.
I concur with Mtn Mike. I had a friend bring his Felt over to the garage with the same exact symptom. The chain would "lift" periodically while on the center ring. When it would lift it would then skip. It only happened on the middle ring (though I believe it can happen on any of the three). In this case the inside of the front derailluer cage was occassionally making contact with the chain. But in this case the contact was at the part of the inside cage plate that is designed to lift the chain for shifting. There could be other more exotic causes for your problem, but the most likely is a front derailluer adjustment issue.
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Old 12-29-03, 12:34 PM   #7
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Thanks all, a thin washer inserted between the middle and large front rings has done the trick. The problem spot on the ring where the chain lifted was the area designed for lifting but was not a deraleur probelm. The middle and large rings appear to simply be too close together for the width of the chain. I am still puzzled that specialized can ship a bike with this problem?
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Old 12-29-03, 12:58 PM   #8
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Quote:
Originally Posted by specialized
Thanks all, a thin washer inserted between the middle and large front rings has done the trick. The problem spot on the ring where the chain lifted was the area designed for lifting but was not a deraleur probelm. The middle and large rings appear to simply be too close together for the width of the chain. I am still puzzled that specialized can ship a bike with this problem?
Wait a minute! Something's wrong here. Those thin washers are not suppose to "fix" the problem you're experiencing. Are you sure your chain is a 9-speed chain originally supplied with the bike?
Also check to see if the large chainring is not bent inward.
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Old 12-29-03, 01:45 PM   #9
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Bike parts are as supplied by specialized! Eyball view of the large ring looks straight but I will take a closer look. Why cant the washers be the solution?
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Old 12-29-03, 01:53 PM   #10
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Originally Posted by specialized
Bike parts are as supplied by specialized! Eyball view of the large ring looks straight but I will take a closer look. Why cant the washers be the solution?
Are these washers specifically made for this application? Are you sure by adding these spacers, you didn't loose the big ring's concentricity?
If you bought this bike from your LBS, have you taken it back to them for a look?
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Old 12-30-03, 05:17 PM   #11
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Good discussion here, but don't all bikes tend to make this noise when running the middle or inner ring with the small cog in back? Thought most everyone avoided these extreme cross-chain combos. Even if you can fine-tune out the noise, I don't believe it's good for the drivetrain, and it's not quite as efficient either as simply shifting up to the big ring and keeping the chain pull perpendicular with the rear axle.
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Old 12-31-03, 08:01 AM   #12
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Originally Posted by HarryK
Good discussion here, but don't all bikes tend to make this noise when running the middle or inner ring with the small cog in back? Thought most everyone avoided these extreme cross-chain combos. Even if you can fine-tune out the noise, I don't believe it's good for the drivetrain, and it's not quite as efficient either as simply shifting up to the big ring and keeping the chain pull perpendicular with the rear axle.
No.

The middle chainring on a three ring crankset wil generally run silent when matched with any of the rear cogs.
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Old 12-31-03, 09:31 AM   #13
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Originally Posted by Don Cook
No.

The middle chainring on a three ring crankset wil generally run silent when matched with any of the rear cogs.
OK, will have to check this out on my new triple bike. Still, not something I'll do as a matter of routine since I don't think it's good for the drivetrain.

Besides, I need every % of the (meager) chain pull I generate making torque, not trying to pull my rear axle to the left!
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Old 01-04-04, 07:27 PM   #14
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OK, will have to check this out on my new triple bike. Still, not something I'll do as a matter of routine since I don't think it's good for the drivetrain.

Besides, I need every % of the (meager) chain pull I generate making torque, not trying to pull my rear axle to the left!
Tried the 39/12 combo today. It works, with just a little jingling noise from the chain hitting the inside of the big ring. I'll normally be in the big ring instead at this speed with 53/17....that is a straight chain lineup for me.
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Old 01-05-04, 06:26 AM   #15
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I had a strange noise in the drivetrain recently that I (and the lbs) couldn't track down. It turned out to be a slightly bent middle chain ring. Seems like that could cause this problem as well. Mine was bent so slightly that it was not that noticeable and only found it when I changed the chainring for other reasons.

Al
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Old 01-06-04, 06:55 PM   #16
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Typically when running a double crank you will experience chain rub on the inside of the large chainring when using the first two (smaller) cogs on the cassette. Shimano and Campy even warn of this in their installation instructions. The triple set-up should give you the second cog with little to no rub, but the smallest cog brings the chain into a angle that will rub on the inside of the large chainring.

Marc
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