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  1. #1
    Ellensburg, WA scozim's Avatar
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    Bent steel ring? Cottered crankset

    I know some cranksets I've had in the past have had a little side to side movement, especially when I mash on the pedals or am standing while climbin.

    On the late 60's Gitane I just finished I was doing some fine tuning and noticing that the crankset seems to have some wobble in it as it rotates around - no pedalling, just spinning it around. Probably a 1-2 mm - can't get a real accurate measurement. I can usually see it fairly well sighting straight down and using the front derailleur cage as my gauge. Wondering if I might have a slightly bent large chainring.

    Any advice on how to accurately check the ring. I tried a level but that didn't seem to work too well. it's a 5 pin crank and the two rings don't separate - just the arm.

    Here's a photo of the crankset - I like it because of the 52-36 gearing.

    1984 Gitane Sprint; 1984 Gitane Tour de France;1982 Trek 610; 1980's Univega Supra Sport (fixie); 1975 Teledyne Titan;1984 Peugeot PSV10N; 1968 Peugeot PL8; ;1982 Nishiki Marina 12; 1972 Peugeot PX-10; 1987 Trek 800 Antelope (touring/commuting set up); 1981 Trek 510; 1993 Trek 950 mtb; 1996 Klein Pulse II mtb; 1997 Klein Pulse Comp mtb; 1989 Peugeot Limestone hybrid (for touring); 1989 Spectrum Titanium

  2. #2
    Senior Moment Peter_B's Avatar
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    I have bent steel chainrings back toward alignment visually by spinning it slowly and seeing where it moves out of alignment and then bend appropriately and judiciously, using Park Tool BT-3.

  3. #3
    26 tpi nut. sailorbenjamin's Avatar
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    A zip tie around the seat tube or down tube makes a handy reference point. Zip it pretty tight and cut the tail down to about 2". I have a pic somewhere but you get the idea.
    Here it is, just do it closer to your crank and farther from your wheel.
    I have spoken.

  4. #4
    Senior Member randyjawa's Avatar
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    I have straightened out a few bent ring sets in my time. I took a couple of pictures and sort of describes the process in this page from my Legnano Nocostalotta feature article on MY "TEN SPEEDS".

    Hope it helps a bit.

  5. #5
    aka Tom Reingold noglider's Avatar
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    Nice crank!
    You don't read my signature anyway, do you?

    Tom Reingold, noglider@pobox.com
    Residences: West Village, New York City and High Falls, NY
    Blogs: The Experienced Cyclist; noglider's ride blog

  6. #6
    Cottered Crank Amesja's Avatar
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    Quote Originally Posted by Peter_B View Post
    I have bent steel chainrings back toward alignment visually by spinning it slowly and seeing where it moves out of alignment and then bend appropriately and judiciously, using Park Tool BT-3.
    A difficult tool to find -you can't even find it on the Park Webpage.

    I just use an adjustable wrench and I think most people do, which is why park doesn't even bother to market this tool any more.

    One could make one out of a piece of 1" x 1/4" steel bar and a chop saw to make a notch at the end easily enough.
    '74 Raleigh Carlton Competition w/ Ultegra | '97 Trek 720 Singletrack CX-er w/ 105 | '64 Raleigh LTD-3 modernized w/ all alloy components |'69 Raleigh Twenty | '54 Raleigh Sports

  7. #7
    perpetually frazzled mickey85's Avatar
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    Assuming a correct setup, if it's warped, I'd pull it off, put it on a flat surface, and use a wedge (wooden) to lift the "low" section a bit. If it's on the edge, do what I do with bent teeth and get a BFW (adjustable, preferably), and give it a twist.
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    Master of the low end garbajj!

  8. #8
    Senior Member
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    Quote Originally Posted by mickey85 View Post
    Assuming a correct setup, if it's warped, I'd pull it off, put it on a flat surface, and use a wedge (wooden) to lift the "low" section a bit. If it's on the edge, do what I do with bent teeth and get a BFW (adjustable, preferably), and give it a twist.
    The BFW indeed.





    I didn't do so well with my odDyssy of straightening a chainring. I bent it little by little, got it just about "right" and then I tried to get it a little more "right" and it was wrong from then on out.
    *Recipient of the 2006 Time Magazine "Man Of The Year" Award*

  9. #9
    26 tpi nut. sailorbenjamin's Avatar
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    I have had one get so far out that is sort of potato chipped. I think the circumference got a little more stretched than the middle. I could pop it from left to right but I couldn't get it to stop in the middle.
    That one got a chain stuffed between it and the other ring to start things off. I had to just start over with a fresh ring.
    Other rings I've had good luck with, though.
    I have spoken.

  10. #10
    Я люблю суп abarth's Avatar
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    You can use the front derailleur cage as a guide. Lower the derailleur until the cage is barely touching the big ring and bend a little section at a time. I've done it many times. Soczim, are you going to the Seattle Bike Swap this year?

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