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Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

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Old 02-08-10, 05:13 PM   #1
Tedisdead
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Bent/shifted seatstays

I was working on my 78 schwinn superior last night and noticed that somehow my seatstays had bent to the right about a quarter inch. The chainstays are fine, but now my brake mount doesn't line up. I'm running it fixed right now, so it's not too big of a deal, but I need to know how to fix it. Is there a way to bend them back without screwing up the whole frame?
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Old 02-08-10, 07:04 PM   #2
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First check to see if the frame is in alignment. If the frame was out-of-whack to begin with, someone (maybe even the factory) may have yanked the stays over to put it into alignment. Or maybe it was just a botched attempt at spreading the dropouts for a wider hub. Sheldon Brown describes a simple method to check basic alignment here:
http://sheldonbrown.com/frame-spacing.html

Scroll down to the section titled "Checking Alignment (Symmetry)"

If it is in alignment with the stays pulled over like that, you'll just have to live with it. The frame was sloppily built, and that's how someone got it to track decently. If OTOH it is NOT in alignment, use the suggestions in the "Spreading the Frame" section to pull it back into alignment.
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Old 02-08-10, 07:22 PM   #3
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Do you have a track hub or a converted rear wheel? The conversion could have been improperly done. I guess even a track hub could have been incorrectly respaced for a six speed if that's what your superior was. If the wheel was centered in the chainstays by eye it might not show.
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Old 02-08-10, 07:22 PM   #4
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I'd say John's suggestion to really do a full on check of the frame alignment is a good one. Some long known good straight edges such as extruded aluminium sections that have been checked for straightness or similar laid along the main traingle tubes so they extend into the rear section will provide a known reference to start checking the rest of the things. Don't tweak anything back at first. Just measure and check everything for alignment to the main triangle's center plain and check all the stays for straightness and the axle for alignment to being perpendicular to the main triangle's flat center plane. Note it's not a center LINE but a center PLANE since the main triangle is made up of three tubes so it decribes a flat two dimensional plane that the rest of the bike must be in proper alignment with. Once you've measured everything and checked everything for straight then sit down and think about all the factors. Only once you have it wired THEN look at bending or tweaking. The tricks and tecnhiques in Sheldon's article are good concepts for some of the techniques for tweaking stuff.
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Old 02-09-10, 03:17 PM   #5
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I'm running a flip/flop hub right now, and I've had this frame for many years. It's gone from the original 10 speed, to a single speed, to a six speed, and now fixed (Rather than buy new bikes, I've always just changed this one). I'm actually going to turn it back into a six speed now for commuting, which led me to noticing this issue. Never noticed it before, and can't remember being hit by a car or anything...
I checked out the Sheldon method first (don't we all?) and the measurements are fine, so I don't want to mess it up by tweaking the chainstay angle/spacing.
I think I'll try Sheldon's 2x4 method with a hub in place. Hopefully, this will keep the spacing intact while moving the thinner seatstays back into place.... right?
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Old 02-09-10, 03:27 PM   #6
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If you went to six speed, that was 126mm, right? Are you sure you have the same amount of spacers on both sides of your hub?
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Old 02-09-10, 09:38 PM   #7
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The hub and axle spacing aren't the issue, the bent seat stays are. I've always either had good luck with my hubs, or spaced the axle to fit the frame. This will be the first frame-tweakage I've ever done. Just wanted to see if anyone had encountered this problem and had a fix.
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Old 02-09-10, 09:52 PM   #8
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I still say to measure up everything as a full on survey so you fully understand where and what is out of place. Only THEN can you take corrective actions that actually mean something. It may be that you need to do the 2x4 trick only on one part of the stays while holding back the other from moving. I say this because it sounds like things moved around in a less than balanced manner. So now they need to be corrected in a less than balanced manner.
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