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  1. #1
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    change to compact chainring without changing cranks

    I have Shimano Dura-Ace cranks and standard 53/39 chainring. I want to change my chainrings to compact chainrings. Is it possibel to change the chain rings without changing the cranks?

  2. #2
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    Quote Originally Posted by khachkar
    I have Shimano Dura-Ace cranks and standard 53/39 chainring. I want to change my chainrings to compact chainrings. Is it possibel to change the chain rings without changing the cranks?
    No. The chainrings wont fit. The bolt circle on your crank is 130mm. On a compact crank the bolt circle is 110mm (that's what makes it "compact") With the smaller bolt circle you can run a smaller inside ring (ie a 34 instead of a 39).

  3. #3
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    right

    Quote Originally Posted by BunnV
    No. The chainrings wont fit. The bolt circle on your crank is 130mm. On a compact crank the bolt circle is 110mm (that's what makes it "compact") With the smaller bolt circle you can run a smaller inside ring (ie a 34 instead of a 39).

    If you look at your inner ring you can see why. The bolt holes are about as far out to the edge as they can be. If the ring were much smaller the bolt holes would be beyond the edge. There are some 38-tooth rings for 130mm bcd cranks, but no smaller.

  4. #4
    kytyree
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    and you can go a little smaller on the outer ring as well

  5. #5
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    Thanks guys. I was hoping it would work. But now that gives me an excuse to buy a whole new crankset. Any good suggestions on carbon? I heard that the SRAM red's have had problems? I also heard that some of the FSA cranks had problems with where the pedal mounts are?

  6. #6
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    R700 - $104

    If your Dura Ace cranks are external BB (7800 or 7900) these are about the easiest swap possible. $104 shipped to you. R700 (Ultegra-ish level) 172.5mm only 50/34. Loosen the pinch bolts, unscrew the bearing adjustment nut, remove old cranks. Reverse the process with the new cranks and adjust the Front Derailler. Go ride.

    Cheap R700 Cranks

  7. #7
    Squirrel Hunter
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    Looking Back

    Quote Originally Posted by khachkar
    I have Shimano Dura-Ace cranks and standard 53/39 chainring. I want to change my chainrings to compact chainrings. Is it possibel to change the chain rings without changing the cranks?
    What cogs are you running now? You may be able to change cassettes and get the gearing you need. Cassettes are far cheaper than cranks.

    So what cassette are you running right now? What gears do you wish you had? What chainrings and cogs do you plan to run with the compact you are lusting after?
    Luck is the intersection of preparation and opportunity.

  8. #8
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    There is a French company Specialites TA that makes a chainring that will become the middle ring and has bolt holes for a 74 BCD ring as the granny gear. http://www.peterwhitecycles.com/chainrings.asp look for the "conversion" chainrings

    Peter_wcc

  9. #9
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    Quote Originally Posted by Peter_wcc
    There is a French company Specialites TA that makes a chainring that will become the middle ring and has bolt holes for a 74 BCD ring as the granny gear. http://www.peterwhitecycles.com/chainrings.asp look for the "conversion" chainrings

    Peter_wcc
    Interesting piece, but the OP seems to want to gear down only slightly (standard to compact) instead of going full bore down to a triple. Besides, at those prices, it might be more expensive to convert to a triple than buy a new compact as per some earlier posts in this thread.

  10. #10
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    I didn't look for it but maybe they have an outer ring 130BCD with a 110 BCD bolt pattern for the inner ring?

  11. #11
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    Took alook at Harris Cyclery site
    http://sheldonbrown.com/harris/chainrings/130.html#ta

    You might be able to use the "Triplizer" ring with pins for the outer and mount a 74 BCD inside of it.

  12. #12
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    It's even less expensive now! Cheap enough to buy the whole crankset rather than new rings for mine. Only have 172.5 mm though so I'll have to resell the crank arms

    Beware there is a noticeable difference in stiffness between this & DuraAce. I think the main reason for this is that Dura Ace (at least 7800) uses a steel axle & the R700 is aluminum.

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