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  1. #1
    Senior Member ScottNotBombs's Avatar
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    Another "Can this crack be fixed?" thread (pic)

    Today is a sad day for my Trek TX770. I went to pull it out of my garage after it sat all winter and it looks like it was at some point damaged. I'm guessing it's time for a new frame, but I thought I should ask in case there is a small chance that it is fixable. The crack is through the seat stay right where it connects to the brake bridge, but it's through the actual seat stay, not a crack in the brazing. Sorry for the bad picture. I can get more if necessary, but my camera was about to die.
    Thank you for your help,
    Scott

    I'm just a kid who gets in trouble sometimes

  2. #2
    Andrew R Stewart Andrew R Stewart's Avatar
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    Scott- If I were to repair this I would suggest removal of the brake bridge, two piece sleeve over the seat stay and reinstall the brake bridge as the economical method of repair. (Won't change frame alignment, no old filler VS new filler issues, less paint damage). The high road repair is to remove the bridge and stay and replace both. Many would say that the only reason to repair this frame is for sentimental reasons. Andy.

  3. #3
    Randomhead
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    I'd be curious how a crack like that could occur, although some older Treks have some dynafile damage that can make this sort of crack much more likely.

  4. #4
    Senior Member ScottNotBombs's Avatar
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    I've been wondering how the crack happened too.. It's strange that it would on the inside of the seat stay instead of the outside.

    What would I use for a sleeve? Would I have to make something out of sheet metal?
    I'm just a kid who gets in trouble sometimes

  5. #5
    Senior Member ScottNotBombs's Avatar
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    I think I found something I could use to make a sleeve. I measured my seat stay at .540", but I figure it will be slightly smaller after the paint is removed. I found .535" i.d. brass tubing with a .014" wall here.
    I'm just a kid who gets in trouble sometimes

  6. #6
    Senior Member mudboy's Avatar
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    You don't want brass. You want steel. And personally, since I'm kinda weird about things being symmetrical, I would sleeve both sides even if the other doesn't need it. You will, of course, need to remove all paint within 4-6" of the area to be brazed, and clean properly with abrasive cloth. Sounds like you have a 14mm stay, a scrap of 16mm stay might do the trick for you as a sleeve, depending upon the wall thickness, or just figure out where on a tapered stay you would need to cut to make a sleeve.

    Pete
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  7. #7
    Randomhead
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    agree w/Pete, brass is no good, you need some 4130 tubing. You should be able to get a good size measurement to find what id you need

    I would probably leave it asymmetric so it can be repaired more easily later

  8. #8
    Andrew R Stewart Andrew R Stewart's Avatar
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    The sleeve method of repair I mentioned would be a split one. Two halves to sandwich the stay. This way the stay won't have to be cut! The sleeve's ends could be shaped to an aesthetic that the rest of the bike suggested. I agree with Pete in the balancing of the look, a sleeve on each stay. Before the current bridge is cut away I'd measure the axle to brake hole and modify it as i saw fit. To center the pads in the caliper's slots or to add more fender clearance. Of course steel, 4130 would be first choice, would be used. I'd also address the crack with a pair of end holes. Bronze/brass would be the filler of my choice. Any other frame mods in the area (like rack mounts or brake cable stops) should be considered at the same time. Andy.

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