Dura-Ace chainring replacement queston
#1
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Dura-Ace chainring replacement queston
My bike has a Dura-Ace FC-7900 crankset of 53-39T configuration. The spec sheet from Shimano says that the "Bolt circle diameter" is 130mm. The Dura-Ace FC-7950 compact crankset, which only comes in one configuration, (50-34T), and with a "Bolt circle diameter" of 110mm. The spec sheet for the FC-7950 says that the 34T chainring (part number Y-1KZ 34000) is Interchangable with the FC-7900 crankset. In fact, the footnotes at the bottom of the FC-7950 spec sheet says, "Same parts".
Is this true? I'm at the age (60 this August), and am pretty big (6' 200lb.) that I could use a little bit of help getting up the steeper, longer hills. Can I swap the FC-7950 34T chainring for my existing FC-7900 39T chainring, (knowing that the FC-7950 specsheet says "Same part", but the "Bolt circle diameter" are different)?
Thank you.
p.s. I really like the 53T and don't want to swap it out for a 50-34T compact crankset.
Is this true? I'm at the age (60 this August), and am pretty big (6' 200lb.) that I could use a little bit of help getting up the steeper, longer hills. Can I swap the FC-7950 34T chainring for my existing FC-7900 39T chainring, (knowing that the FC-7950 specsheet says "Same part", but the "Bolt circle diameter" are different)?
Thank you.
p.s. I really like the 53T and don't want to swap it out for a 50-34T compact crankset.
#2
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Nope. 130 is too large for anything smaller than 38t. FWIW, the tech docs for the 7950 on Shimano's site specify "B" interchangeability with FC6650/6650G (i.e., other compacts).
#3
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smallest that will fit on a 130mm bolt circle is a 38T if you can find one. maybe it's time to go to a wider range cassete with a midcage rear derrailleur?
#4
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Thanks guys. The bike came with an 12-27 cluster and I changed it to an 11-27, (by adding an 11T and removing the 16T). The largest Dura-Ace rear sprocket available is a 28T. Not worth the cost for one extra tooth. Maybe it's time to go with a 50-34T compact crank.
Is the right-hand crank easy and quick enough enough to swap back and forth, (depending on the ride I'll be doing), between the 53-39T and a 50-34T?
Is the right-hand crank easy and quick enough enough to swap back and forth, (depending on the ride I'll be doing), between the 53-39T and a 50-34T?
#5
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Never mind. At $500, I'll live with the 53-39T. I'll just have to get into better shape to pull the hills.
#6
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(6 feet and 140 pounds here)
#7
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