Broken downtube to bottom bracket - can it be safely repaired?
04-07-21, 12:24 PM
#1
Destroyer of Wheels
Thread Starter
Broken downtube to bottom bracket - can it be safely repaired?
This seems terminal. I saved my Nishiki Sport from a backyard in 2006 and built it up over the years through hours of browsing threads here. Only fitting to get a final opinion from where it was born from. I'm a high Clydesdale (used to be mid...thanks Covid), this is the second time a part of the frame broke (the first was where the chainstay met the rear wheel). Took me a few miles to figure out where the knocking was coming from, looked down, gut punch.
Open to any thoughts, thanks!
Open to any thoughts, thanks!
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04-07-21, 12:48 PM
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You might want to ask the mods to move this thread to the Framebuilders section of the forum.
That said, that's probably not the only joint that was close to failure---it's just the joint that happened to fail first. Same applies to the first broken chainstay.
That said, that's probably not the only joint that was close to failure---it's just the joint that happened to fail first. Same applies to the first broken chainstay.
04-07-21, 01:31 PM
#3
Destroyer of Wheels
Thread Starter
Yeah...that's my thought too. It was in a backyard for a few years, metal fatigue doesn't usually get better over time and NYC streets aren't kind.
Good thought about the Framebuilder section, thanks!
Good thought about the Framebuilder section, thanks!
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04-07-21, 02:20 PM
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Clark W. Griswold
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I mean do you really want to save a backyard find that isn't a super high end bike? It is up to you. It might be saved but it will probably cost more than the bike is worth and it sounds like you have put some time on it so it might be time to let it go. Especially as a Clyde you don't want to risk it over that.
04-07-21, 03:51 PM
#5
Destroyer of Wheels
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I mean do you really want to save a backyard find that isn't a super high end bike? It is up to you. It might be saved but it will probably cost more than the bike is worth and it sounds like you have put some time on it so it might be time to let it go. Especially as a Clyde you don't want to risk it over that.
But I agree with you, if the only solution was essentially disassembling the frame and machining a new BB only to worry where the next point of failure will crop up, it's better to start putting effort into something new.
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04-07-21, 04:58 PM
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this was a Lotus with a similar failure repaired by a local motorcycle shop
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04-07-21, 05:01 PM
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Yes, in principle it can be repaired, but unless there's great sentimental value in the bike, or you're willing and able to do the work yourself, it's likely not worthwhile.
There are four tubes that come together in the bottom bracket shell. The simplest fix, if it is only the shell that has failed and the tubes are intact, is to make several cuts in the shell, sweat off the pieces individually, fit a new shell and braze it in place. It's still a lot of work. If one or more of the tubes themselves have failed, then those would also have to be replaced. At that point, you're looking at the cost of a new custom frame.
There are four tubes that come together in the bottom bracket shell. The simplest fix, if it is only the shell that has failed and the tubes are intact, is to make several cuts in the shell, sweat off the pieces individually, fit a new shell and braze it in place. It's still a lot of work. If one or more of the tubes themselves have failed, then those would also have to be replaced. At that point, you're looking at the cost of a new custom frame.
04-07-21, 05:16 PM
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To do it, I would at minimum: Remove the bottom bracket assembly, cabling, hardware within the area of the issue, grind down to bare metal the area with separating metal sections, have it tig welded together. Then, make a "pie" cut out of new tube material to wedge in the distressed area following up with it being tig welded in place. Prep the surfaces with primer, finish it off with paint, & apply a clear coat. Reassemble the parts.
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04-07-21, 05:41 PM
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Clark W. Griswold
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Well...worth is subjective, right? I spent over a year dialing it in till it was perfect, where 80 mile rides didn't feel much longer than 30 and put thousands into it over the years. What's that time, sunk cost, comfort, and familiarity "worth"? A lot...to me! It was my fourth bike, and the only one I could get to feel like a body part while riding. I figure a new bike will require the same energy to get to hopefully about the same level. If there was an easy fix, it would be worth it.
But I agree with you, if the only solution was essentially disassembling the frame and machining a new BB only to worry where the next point of failure will crop up, it's better to start putting effort into something new.
But I agree with you, if the only solution was essentially disassembling the frame and machining a new BB only to worry where the next point of failure will crop up, it's better to start putting effort into something new.
