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Are the two pulleys on a Shimano Dura Ace 9 speed rear derailleur interchangable (i.e., are they exactly the same)? Are they generally interchangable on other rear derailleurs?

Thanks!
 

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The top pulley is usually a ceramic (high end) or steel bushing design. It is made to float side to side a bit and still run smooth so that there is a little forgiveness with the STI shifting to keep things quiet. The bottom pulleys are sealed bearing or bushings with no side to side float because it isn't needed.
 

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most old friction derailler pulleys are.

I put some suntour sealed bearing pulleys in my mavic 851 derailler and had to slide the pulley cage down about a centimeter bc the suntour pulleys were fatter than the mavics and were making contact with where the pulley cage attaches to the main body.

I've swapped out other pulleys in the past and never had a problem. The above wasn't really a problem either, just made my pulleys slightly further from the cogs.

and actually your ? asks within a given derailler I think and that I believe the answer is yes (which was already stated).

babble babble babble....
 

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Learn by looking

MPH74 said:
Are the two pulleys on a Shimano Dura Ace 9 speed rear derailleur interchangable (i.e., are they exactly the same)? Are they generally interchangable on other rear derailleurs?
An awful lot about bicycles can be determined by simple inspection. If you look at the pulleys on a modern derailleur, you will see that they are marked very differently. One may have a directional arrow on it, and the other may be marked specifically for 10s or 9s. These differences alone would suggest that they cannot be swapped. A simple wiggle will also show you that the top pulley can slide from side to side (what Shimano used to call Centertron, or something like that) while the bottom one does not move.
 
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