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I am looking to replace 2 of the 3 chainrings on my Ultegra triple. I want to replace the 52 and 42 with a 53 and 39. All I have found are 53/39 replacement chainrings for double cranksets. Will these work on my triple?
 

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The double 39 ring does not have the ramps and pins to assist the chain to shift up from the granny 30 to the 39. TA Specialties (Alize) and FSA have chainirngs designed to run in the middle. I replaced the chainirngs on my wife's Ultegra triple with TA Specialties Alize rings, 28-39-49. It took some fine tuning to get the shifting smoothed out but they work well now.
The Ultegra 9-speed tripple front derailleur is designed to work best with a 10-tooth differential between the big and middle rings. The 9-speed triple Dura-Ace derailleur was designed to run with 30-39-53 rings. I believe I'd try staying with the 52.
I bought my TA Alize rings from Sheldon Brown / Harris Cyclery. They are also available from Peter White.

Al
 

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Al1943 said:
The Ultegra 9-speed tripple front derailleur is designed to work best with a 10-tooth differential between the big and middle rings. The 9-speed triple Dura-Ace derailleur was designed to run with 30-39-53 rings. I believe I'd try staying with the 52.
I had an Ultegra 9-speed triple derailleur and then switched to a 52-38-30 setup (I bought a TA middle ring). Shifting was bad and it was hard to eliminate chain rub in the middle ring since the derailleur was designed for a 10-tooth difference. The cage gets narrower below the level where the chain would be on the 42T chainring.

I bought an Ultegra 10-speed derailleur, which is designed for (I think) 52-39-30. It works OK, but the cage is slightly narrower, so I end up with some gear combos where the chain rubs no matter what I do.

Long story short: if you make this change, shifting may suffer unless you get a 9-speed Dura-Ace derailleur.
 
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