Advertise on Bikeforums.net



User Tag List

Results 1 to 7 of 7
  1. #1
    Senior Member
    Join Date
    Aug 2007
    Location
    Baltimore, MD
    My Bikes
    Tommasini Sintesi ~1998
    Posts
    66
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Campy compact crank conversion?

    I have Chorus 8-speed on my ~1998 steel bike, with front sprockets 52 and 39 teeth and a brazed-on front derailer, and a 26-tooth gear in back I'm trying to figure out how to change to a compact crankset for lower gearing. My questions are:
    1. Are compatible compact cranksets available for this bike?
    2. Would I need to change the front derailer? If so can I use the same braze, or would I need to go to a ring mount?
    Thanks for any advice.
    Tommasini Sintesi ~1998

  2. #2
    Gear Combo Guru Chris_W's Avatar
    Join Date
    May 2007
    Location
    Switzerland
    My Bikes
    Spec' Tarmac (road), Spec' Secteur Disc (commuter & tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder), a train pass, and NO car :)
    Posts
    2,091
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    You should be able to get a compact for this bike, but as well as the crankset, you will probably also need to change the bottom bracket. Hopefully your current BB will come out without a struggle, but there can occasionally be problems with getting ones out of 10-year old bikes that have never been removed before.
    There shouldn't be any need to change your front derailleur. At least, try it with your current one and only consider changing it if you are not happy with how it performs.
    One more thing to consider, modern cranksets are made for 9, 10, or 11 speed chains, so the chainrings are slightly closer together. You'll still be able to use your 8-speed chain, but it may rub on the large ring when on the small ring and you use the smaller cogs in the back. You could avoid this by using a 10-speed chain (while still using the 8-speed cassette and derailleurs).

  3. #3
    Senior Member
    Join Date
    Oct 2008
    Location
    Ohio
    My Bikes
    Franklin Frames Custom, Rivendell Bombadil, '83 Specialized Stumpjumper
    Posts
    1,289
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by yellowcanoe1 View Post
    I have Chorus 8-speed on my ~1998 steel bike, with front sprockets 52 and 39 teeth and a brazed-on front derailer, and a 26-tooth gear in back I'm trying to figure out how to change to a compact crankset for lower gearing. My questions are:
    1. Are compatible compact cranksets available for this bike?
    2. Would I need to change the front derailer? If so can I use the same braze, or would I need to go to a ring mount?
    Thanks for any advice.

    1. You can use any compact crank(as well as any other crank) on your bike.(Though you wouldn't want a mtb triple! )

    2. You can use your current FD with a compact crank.

  4. #4
    Senior Member
    Join Date
    Aug 2007
    Location
    Baltimore, MD
    My Bikes
    Tommasini Sintesi ~1998
    Posts
    66
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thank you both! I'm thinking of changing out the Chorus 52/39 crankset to a 1 or 2 year old Centaur 50/34 so that I can stay with alloy - should I expect any deterioration in the shifting? Do you anticipate any need to change the RD to a longer cage (this would probably kill the plan). Thanks again!
    Tommasini Sintesi ~1998

  5. #5
    slow as I ever was Ex Pres's Avatar
    Join Date
    Dec 2007
    Location
    an imposter living in the 35223
    Posts
    5,780
    Mentioned
    5 Post(s)
    Tagged
    0 Thread(s)
    You'll have to swap the BB from your 102mm to a 111mm (Centaur or AC-H)

    Total Chain wrap currently 13-26 + 52-39 = 13+13 = 26 (I'm assuming 13 small cog)
    proposed 13-26 + 50-34 = 13+16 = 29

    29 is probably doable, but at the limit. I'm running 27 and it would appear to have some room.

    Velobase.com lists the max chain wrap on some earlier Chorus at 25. I ran an early one at the same 27 w/o issue.
    Last edited by Ex Pres; 09-08-09 at 08:55 AM.
    72 special CNC ______ 72 Frejus (ala Legnano) _73 Holdsworth Record
    80 Ranson__________ 80 unknown French____ 83 Trek 600 (620 styled)
    85 Gianni Motta_____ 90 Miele Gara ________ 02 Casati Dardo #1
    02 Casati Dardo #2 __ 03 Casati Dardo ______ 08 BF IRO (fixed/SS)
    09 Dogma FPX magn_ 10 Vassago Fisticuff (IGH)

    For Sale: _________ 78 Raleigh Professional __ 82 Peugeot PXN10
    85 Trek 560_______ 88 Guerciotti GLX

  6. #6
    Senior Member
    Join Date
    Sep 2008
    Location
    Loveland, CO
    My Bikes
    Two LOOK 585s, one KG461
    Posts
    4,987
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    A 1-2 year old crank would be the new UT outboard bearing type, made for 10 speed. An old 8 speed chain might be too wide. A 9 speed might work better.

    Chain wrap should not be a problem. Campy listed the wrap to correspond to the chainring and cassettes they sold, not the true maximum wrap. The short cage length has not changed in a long time, but my 11 speed short cage and wrap a 50/34 with an 11-27 (11 speed).

    The way to tell is to set the chain length using the big/big plus one inch method first, then double check for the chain hanging loose in the little/little (through the RD in the normal fashion). I use the little/little method exclusively, since I know I'm no exceeding the max. wrap capacity.

  7. #7
    Senior Member
    Join Date
    Aug 2007
    Location
    Baltimore, MD
    My Bikes
    Tommasini Sintesi ~1998
    Posts
    66
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks Dave - Branford agrees with you that a 9 speed chain should work well, along with 0.6 mm spacers between the rings. Thanks also for the chain length info. Am getting the 2008 Centaur UT 50/34. Any advice out there on facing and tapping in BB that formerly held the internal BB, now changing to the outboard bearings - is this necessary? - if so I suppose I should have it done by the LBS as I have no experience with this?
    Tommasini Sintesi ~1998

Posting Permissions

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