Chain rubs against Rear Derailleur?!

monteverest

New Member
I just had my rear derailleur replaced. After one ride, I discovered that the chain actually rubs against the rear derailleur and chain while the chain is in the smallest chainring and either of the smallest two cogs. In these gears, the rear derailleur is actually parallel to the ground and the chain slides against it.

Before I apply self-help or take the bike back to lbs, does anyone know what the problem could be? My initial hunch is the derailleur cage is too short for the chain?
 
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SpartaBard

Well-Known Member
Team MTBNJ Halter's
I am far from an expert in the Shop Talk forum (as my avatar and sig line indicate), but an easy fix is to just not use the combo of the small chain ring and the small cog. Instead just move up to your middle ring. It is sometimes difficult to adjust the dérailleurs for that small cog.

First questions really should be this though: Do you remember bumping your rear der. on a recent ride?

Did you install it or your lbs? If your lbs did, you can always swing buy. They should be happy to fix it for you.
 

monteverest

New Member
Photo of Rear Derailleur

Thanks for your replies. Here are two pictures of the derailleur with the bike turned upside down. While in the smallest chainring and the two smallest cogs, the derailleur no longer extends but contract up, causing the chain to rub against the chain and rear derailleur.

I just bought this derailleur and the shop installed it. I'm taking the bike back to the shop tomorrow but would like to fix it myself if the problem is minor.

The other option is to stay off these gears (chaincrossing gears anyway) but sometimes I need the easy cog to climb.

I don't recall hitting anything; took it on just one ride after having it replaced.
 
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Mk1Racer

New Member
I'm certainly no expert, and I didn't even stay at a Holiday Inn Express last night, but my first guess, looking at the pictures, is that your chain is too long.

And you've already covered the obvious chain-crossing issue. And I'm curious, why would you use those gears to climb, rather than moving up to the middle ring and a cog further up the stack?
 

Norm

Mayor McCheese
Team MTBNJ Halter's
Looks like there's a big scrape on the derailleur so it may have wacked something. Chain could be too long. In general small-small combos are not the best idea.
 
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Stan LeCupp

Guest
Just take a link or two out of the chain. Be careful not to make it too short. You should still be able to shift into a big cog to big chain ring combo.
 

ChrisG

Unapologetic Lifer for Rock and Roll
Could be the chain is too long, but the key issue here is the cross-chain.

You should be able to get the same gear ratio in your middle ring with no issues.

Your chain and cogs will thank you.:)
 

pixychick

JORBA: Ringwood
JORBA.ORG
I too am no expert on this, nor have I stayed at Holiday Inn express, just an observer of mishaps of my own. In the picture the chain looks long, but the derailer looks wrong too. Could it just be your DR has jumped it's tab that hold it in place ? I once had a DR shift on me, after putting it on myself on vacation.

hopefully jdog will chime in soon. ?? If not, I would take it back to the shop to have them check, if you are not familiar with how to put a DR on.
 
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Stan LeCupp

Guest
This is just a thought but.. is it possible the shop replaced a long cage derailleur with a mid or short cage one. I'm not sure but if your running all 3 chain rings a mid cage may be border line. Short cage would most likely not work.
 

anrothar

entirely thrilled
i'm gonna go right ahead and say that i am an expert on this, and your chain is definitely too long.
 

ytc100

New Member
If a short cage derailleur was installed with the same length chain could the chain appear to be too long but not be?
In other words is it still the right length for big big combo but seems too long because of the shorter distance between der. pulleys when shifted onto the smaller gear combos?

How does the derailleur behave in the big big combo?
 

Frank

Sasquatch
i'm gonna go right ahead and say that i am an expert on this, and your chain is definitely too long.

Sean, I was totally disappointed in the fact that there was no "single speeds don't have this problem" comment.

And from the bikes I've owned, the chain will rub like that in granny frt and high rear.
 

TJYeti

Knows about bikes
Chain looks to be too long - and in need of lube. The shop the did the repair should have picked up on this. If you want to come down to me in denville I'll take care of it. Home and shop both in dville, let me know. Home = free, shop = give boss a few bucks. Looks like the cassette could be cleaned too, I hate rust!
 

monteverest

New Member
Removed Link from chain

Took the bike back to the shop and they removed a link from the chain. Also told me the cage is "long" so it must have been the chain. Maybe the chain got stretched somewhere between breaking the RD and installment of the new RD.


Haven't rode the bike yet but tomorrow will be the day of reckoning. The RD slants towards the handle bars when the gears are in large-large combo which I guess is normal.

Thanks for everyone's help ...
 

SpartaBard

Well-Known Member
Team MTBNJ Halter's
Took the bike back to the shop and they removed a link from the chain. Also told me the cage is "long" so it must have been the chain. Maybe the chain got stretched somewhere between breaking the RD and installment of the new RD.


Haven't rode the bike yet but tomorrow will be the day of reckoning. The RD slants towards the handle bars when the gears are in large-large combo which I guess is normal.

Thanks for everyone's help ...

There is really no need to ever be in a "large-large" or a "small-small" combo. If you find yourself using them, you should be in your middle ring.

Glad its all better for you. Now get out and ride!
 

Mk1Racer

New Member
Took the bike back to the shop and they removed a link from the chain. Also told me the cage is "long" so it must have been the chain. Maybe the chain got stretched somewhere between breaking the RD and installment of the new RD.


Haven't rode the bike yet but tomorrow will be the day of reckoning. The RD slants towards the handle bars when the gears are in large-large combo which I guess is normal.

Thanks for everyone's help ...

I'm surprised that they only took one link out. And the shop should have checked the chain when they put the new RD on. If it was stretched, they should have suggested a new chain. Regardless, it shouldn't have left the shop like that.
 

CycleBoy

Sussex Bike and Sport
Shop Keep
The reason the chain didn't rub with the old derailluer is because the spring was worn and not as strong as the spring on the new one. Also, any time you can avoid breaking an old stretched chain, the better. In your case, it was not so much an issue since you had a SRAM chain which uses the power link and not the lowsy connector pins like Shimano uses. The chain has been too long since you've had it. Chains stretch, but not that much. Hopefully that solved everything. Let me know if anything acts up. I'm not a fan of cross over gears either, but I guess you do what works for ya.
 
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