Advertise on Bikeforums.net



User Tag List

Results 1 to 8 of 8
  1. #1
    weirdo
    Join Date
    Jan 2006
    Location
    Louisville, KY
    My Bikes
    Viner Pro Carbon,Fat Chance Yo-Eddie, Specialized S-Works (epic), Voodoo Rada, Trek 830 setup SS for commuting.
    Posts
    97
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Chainring compatability

    I am replacing the chainrings on an old 21-speed (7-speed w/ tripple). If I replace the Big and Middle rings with 9-speed rings, will I need to space them out to run a 7/8 speed chain, or is the spacing on the spider.

  2. #2
    Your mom
    Join Date
    Aug 2006
    Posts
    2,546
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Chainring spacing is generally universal by manufacturer. I think Shimano likes a 110 BCD (bolt center diameter) and Campy 144. But don't quote me. So, the most important thing is to do some research to find the BCD of your current crank (Sheldon has a database), and to get chainrings with the same BCD. Chainrings are not speed-specific.

  3. #3
    weirdo
    Join Date
    Jan 2006
    Location
    Louisville, KY
    My Bikes
    Viner Pro Carbon,Fat Chance Yo-Eddie, Specialized S-Works (epic), Voodoo Rada, Trek 830 setup SS for commuting.
    Posts
    97
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I'm not talking about the BCD spacing, I am talking about the spacing between the rings so that the wider 7-speed chain will won't rub on the 9-speed rings. Technically if you are running a n speed, you want the rings a little closer together so that the chain won't drop inbetween rings. So to clarify a little. If I have a tripple set up for 7-speed. I pull the Large and middle rings and replace them with 9-speed rings will the top two rings sit closer together and leave a larger gap between the 2nd and 3rd ring that could potentially cause problems shifting between granny and middle, or is the lateral spacing dictated more by the spider on the crank than the width of the chainring?

  4. #4
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    25,759
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    Note to Tellyho: Shimano uses a 130 mm BCD for road cranks and chainring spacing isn't universal.

    When they went from 8 to 9-speed, Shimano offset the middle ring (or small ring on a double) slightly toward the outside to get it closer to the big ring. AFAIK, the spider arms remained the same thickness and the big rings didn't change either. So if you want to use an 8-speed chain with 9-speed rings, you will probably need to add thin spacer washers between the inner ring and the spider arms.

    BTW, you could use a 9-speed chain and not have to respace the crank. The rear shifting shouldn't care.

  5. #5
    weirdo
    Join Date
    Jan 2006
    Location
    Louisville, KY
    My Bikes
    Viner Pro Carbon,Fat Chance Yo-Eddie, Specialized S-Works (epic), Voodoo Rada, Trek 830 setup SS for commuting.
    Posts
    97
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks this is what I needed to know.

    Also about BCD. For shimano 130BCD standard, but they do make a compact with 110BCD

  6. #6
    me have long head tube TallRider's Avatar
    Join Date
    Oct 2005
    Location
    Chapel Hill, NC
    Posts
    4,097
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Flanderflop
    Also about BCD. For shimano 130BCD standard, but they do make a compact with 110BCD
    Lots of people have made cranks with 110mm BCD. Shimano's early mtb cranks had this (with 46/36/26 chainrings), and earlier Sugino triple cranks on touring bikes had 110mm also.

    Current Shimano compact-double cranks for road bikes are also 110. FSA and others have been making compact double cranks in 110mm for awhile now too.

    Also, Campy's modern cranks have 135mm BCD - 114 is older thing that now only shows up on track cranks.

  7. #7
    Senior Member
    Join Date
    Aug 2005
    Location
    Pittsburgh, PA
    My Bikes
    '''96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '12 Surly Pacer, All are 3x8,9 or 10. It is hilly around here!
    Posts
    25,759
    Mentioned
    6 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by Flanderflop
    Also about BCD. For shimano 130BCD standard, but they do make a compact with 110BCD
    Correct but Shimano's "compact" road cranks are relatively new products and their older and most current road cranks are all 130 mm BCD.

  8. #8
    Your mom
    Join Date
    Aug 2006
    Posts
    2,546
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I stand corrected. Not sure how the 110 figure wound up in my head, as I have an old set of 130 BCD 600 cranks. I had no idea that spider thickness might have changed. I ALWAYS learn something on this board.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •