Changing 52 to 50 on DA 7800 triple chainset

normanp
normanp Posts: 279
edited July 2011 in Workshop
Is this possible? The 52 is a bit big. I'm not sure whether this: http://www.amazon.com/Shimano-Dura-Ace-FC-7800-10-Speed-Chainring/dp/B001GSSBQK would be OK. What does 'B-Type' mean?
Thanks

Comments

  • Rule74Please
    Rule74Please Posts: 307
    How is the 52 a bit big?

    A 50 will just be the same as using 1 gear lower.

    If the 52 is a bit big stay on the 39
    Don't know the Rules?

    http://www.velominati.com/blog/the-rules/
  • avoidingmyphd
    avoidingmyphd Posts: 1,154
    A and B is to do with the gadgets on the chainrings that make shifting smoother. They are aligned so A rings shift smoothly to other A rings and B rings to other B rings.

    Sheldon will explain http://sheldonbrown.com/dura-ace.html
  • Bobbinogs
    Bobbinogs Posts: 4,841
    Might be a lot cheaper looking at changing the cassette, particularly if you drop to Ultegra or something equivilent.
  • satanas
    satanas Posts: 1,303
    Shrinking the outer ring by 2 teeth is going to make sod all difference to the gearing, but is quite likely to stuff up front shifting. Apart from the shifting ramps and pins not lining up, you may need to change the front derailleur to one intended for a 50x39 combo as the DA 7800 mech might not shift down off the big ring properly unless lowered, and if you lower it the inner cage plate is likely to foul the middle ring. Better to change the cassette to one with a larger small cog (i.e., Ultegra 13-25), and quite possibly cheaper too. Or just don't use top gear. Or get a different crankset with all 3 rings smaller.

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