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Discussion Starter · #1 ·
My girlfriend bought a new road bike with a complete Shimano 105 9 speed group. She wanted a compact crank, so I bought and installed a Truvativ Rouleur GXP 50-36 crankset. Everything is brand new.

Keep in mind I am hearing this noise on the trainer......

Everything runs smoothly until shifting into the 4 outermost gears on the cassette. At that point you can feel and slightly hear a grinding noise. Almost the sound you get when a bearing is missing. Shifts well, rear derailleur seems to line up well, and the chain is also clear of the front derailleur.

Am I missing something obvious? This is my first go'round with a compact crank, but I didn't think there were any compatibility issues.

Thanks~
 

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Possibilities

morgan1819 said:
Everything runs smoothly until shifting into the 4 outermost gears on the cassette. At that point you can feel and slightly hear a grinding noise. Almost the sound you get when a bearing is missing. Shifts well, rear derailleur seems to line up well, and the chain is also clear of the front derailleur.
When you say everything is brand new, can we assume chain and cassette? If not, the first suspect would be a worn (and therefore elongated) chain not seating well on the chainrings. If the chain is new, it might be that you still have the factory wax on there instead of real chain lube (ProLink or 4 parts Odorless Mineral Spirits:1 part motor oil are popular favorites). Also, you might try turning the RD barrel adjuster 1/4 turn in either direction and see if that helps. If it gets better, turn some more to optimize. If it gets worse, go back in the other direction. There is no inherent incompatibility with compact cranks.
 

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You might check to see if the cassette lockring is loose.
 

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Resident Dutchbag
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morgan1819 said:
My girlfriend bought a new road bike with a complete Shimano 105 9 speed group. She wanted a compact crank, so I bought and installed a Truvativ Rouleur GXP 50-36 crankset. Everything is brand new.

Keep in mind I am hearing this noise on the trainer......

Everything runs smoothly until shifting into the 4 outermost gears on the cassette. At that point you can feel and slightly hear a grinding noise. Almost the sound you get when a bearing is missing. Shifts well, rear derailleur seems to line up well, and the chain is also clear of the front derailleur.

Am I missing something obvious? This is my first go'round with a compact crank, but I didn't think there were any compatibility issues.

Thanks~

This may be a bit redundant but sometimes these things are overlooked. When you exchange cranksets you most likely end up with a different chainline and you have to adjust your RD a little.
 

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Palm trees & sunshine!
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rogger said:
This may be a bit redundant but sometimes these things are overlooked. When you exchange cranksets you most likely end up with a different chainline and you have to adjust your RD a little.
That would be my first look.
 

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Squirrel Hunter
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Chainring Rub?

morgan1819 said:
...50-36 crankset...
...the chain is also clear of the front derailleur...
When in the small chainring and crosschaining could the chain be rubbing against the lower portion on the inside of the big chainring? When you consider the chain angle, flex and gap between the 50-36 it may be something to look at.
 

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The chain should be shortened if you switch from a standard crank to compact. If it is too long the der may not be able to take up the slack and the chain can rub against the der cage. Select the smallest gear ration possible and look at the der from the side. Ensure that once the chain exits the lwr der pulley that it doesn't come in contact with the der again on its way back to the front chainring.
 

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catskillclimber said:
The chain should be shortened if you switch from a standard crank to compact. If it is too long the der may not be able to take up the slack and the chain can rub against the der cage. Select the smallest gear ration possible and look at the der from the side. Ensure that once the chain exits the lwr der pulley that it doesn't come in contact with the der again on its way back to the front chainring.
That's my vote--the top jockey wheel in the der. is probably bumping the cassette as the chain lengthens. Tightening the screw that controls the angle of the derailler so it's more extended should help. Wish I had the terminology to be really helpful, but maybe you get the idea.
 

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Discussion Starter · #9 ·
bingo..

thanks for the help everyone. it does appear the chain needs to be shortened a bit. i adjusted the rear derailleur as much as i could in order to prevent the pulley from making contact with the cassette, but it wasn't quite enough.
 
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