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  1. #1
    Senior Member
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    First Road Bike Build / Rear Derailleur Questions

    I've only built BMX and Track bicycles in the past and I've decided its time to build a road bike. I'm building my first roadie out of classic 80's campagnolo parts. Everythings going great. I have the bottom bracket, cranks, headset, stem, handlebars, brakes, seatpost, saddle, all installed (80's campy super record except for the bars and stem which are cinelli) and it seems everything else will fall into place smoothly because its all very familiar...except for one thing.
    DERAILLEURS. They are completely foreign to me.
    Just by looking at the rear derailleur (which is an '84 Campy Super Record) I can figure out which screws are the "high" and "low" stop screws and where the shift cable attatches. Thats about it. Is there more I should know?
    QUESTION: When I bolt the derailleur to the hanger on the frame, and with no chain or shift cable installed, the derailleur hangs pretty loosely. Is the derailleur meant to pivot on the hanger bolt? There is a small tab on the derailleur and on the frame hanger that prevents the derailleur from moving too far forward, but it pivots quite a bit back and forth.
    QUESTION: Theres a screw that can best be described as "bullet shaped" right next to the main pivot. What does it do? Heres a pic:
    Thats not mine. Just a photo I found online. I've circled the screw in question.
    LASTLY: The stop screws on that derailleur in the photo I found dont have springs exposed. The high gear stop screw on mine is identical to the one in the photo. It has that same plastic piece instead of an exposed spring. My low gear stop screw spring is exposed instead of encased. Whats the difference between that plastic piece and the spring? Mine is cracked a bit.
    Thanks to anyone who might have any insight. I don't expect anyone to respond to this incredibley long and detailed post, much less read the whole thing, but I thought it would be worth a shot. If you've even read this....thanks.

  2. #2
    Senior Curmudgeon
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    The derailleur will be held by spring tension against the adjustment screw that moves it forward and back against the stop. The chain will create the tension in the derailleur springs.

    The travel stop screws typically are held in place by the friction of the plastic.

    For good adjustment advice, visit the local book store & stand around reading Leonard Zinn's "Zinn and the Art of Road Bike Maintenance." Maybe drink some coffee...

    Lastly, I think the "bullet shaped screw" is just a spring retainer stop, but I'm just guessing. I don't think you're intended to mess with it.

    Cheers & post pictures when you get your ride together!

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