Advertise on Bikeforums.net



User Tag List

Results 1 to 6 of 6
  1. #1
    crusty jbrians's Avatar
    Join Date
    Aug 2005
    Location
    Guelph, ON
    My Bikes
    Giant Kronos, Miele Appolo, Miele 12 spd, Diamondback Hybrid
    Posts
    309
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    Chainrub with compact crank

    I'm pretty much sure what the answer is but here goes.
    All 105 (9)sp components with a 105 external 50-35 Crank.
    I ride a smaller bike so the chainstays are short. On the 34-12 rings (small, small) the chain catches on the pins on the 50 ring. If I shift up to the 13 the issue goes away. Obviously the chainline has changed.
    Has anyone had any luck with shimming the crank out a mm or two?
    Around and around we go!

  2. #2
    Senior Member
    Join Date
    Aug 2009
    Location
    North of Boston
    My Bikes
    Kona Dawg, Surly 1x1, Karate Monkey, Rockhopper, Crosscheck , Burley Runabout,
    Posts
    2,119
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    You will get better resluts not using the 2 extreme gears, small, small and large large. 2 mils might work well.

  3. #3
    Senior Member
    Join Date
    Apr 2009
    Location
    New Rochelle, NY
    My Bikes
    too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
    Posts
    22,556
    Mentioned
    69 Post(s)
    Tagged
    1 Thread(s)
    As you imply knowing already, it's a combination of the chain coming from the extreme outside to the inner. Generally it's best to avoid riding crossed over, but there are situations where you might want to for a while, and IMO a bike should be set up so you can.

    You have two choices.
    You can modify the chainline but I'd check first to see on which side of dead center it is already. If it's already toward the outside of the cassette's center, you might not want to move it farther out, lest performance on the inner cassette sprockets suffers.

    You might also use small shims to increase the chainring separation a hair, but be careful not to add so much that the chain hangs on shifts to the 34t chainring.

    In your shoes, I'd start by checking the chainline. If it's a bit inboard, and was easy to correct I'd go ahead and move it out, but otherwise I'd probably just live with things as they are.
    FB
    Chain-L site

    An ounce of diagnosis is worth a pound of cure.

    “Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin

    “One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN

    WARNING, I'm from New York. Thin skinned people should maintain safe distance.

  4. #4
    Senior Member
    Join Date
    Oct 2005
    Posts
    5,438
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Its the nature of the beast to get chain rub on the small/small with that set up. Its the 15 tooth difference between the 50 and the 35 that makes in inevitable that you will have the chain rub. I have a 53/39 and mine does the same thing and I've got a great chainline. Just don't use that gear combo.
    Il faut de l'audace, encore de l'audace, toujours de l'audace

    1980 3Rensho-- 1975 Raleigh Sprite 3spd
    1990s Raleigh M20 MTB--2007 Windsor Hour (track)
    1988 Ducati 750 F1

  5. #5
    crusty jbrians's Avatar
    Join Date
    Aug 2005
    Location
    Guelph, ON
    My Bikes
    Giant Kronos, Miele Appolo, Miele 12 spd, Diamondback Hybrid
    Posts
    309
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    thanks for the replies. I pretty much stay away from the 34-12. I'm not worried about the chainline hurting anything but I hate the noise. It has got to be causing wear on the pins as well.
    It is a ratio that I like and the extra shifting to get to a similar gear on the 50 is often a nuisance.
    Comapct cranks have their uses but I sometimes think I would be better going back to a 53-39 and just getting a cassette with a few cogs with higher teeth counts.
    Around and around we go!

  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)
    Switch to a cassette that starts with an 11 and/or quit using the small/small. Shimming the crank is not a proper solution, except in the rare case where it's really off.

Posting Permissions

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