# Cracked steel frame. Repairable?



## Kevin_Federline (Nov 19, 2008)

Tig welds only. Keep the heat down and it will be good as new!


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## Hardtails Are Better (May 4, 2005)

So my much beloved steel DH bike has a crack in the seat tube. Due to a crash some years ago, the seat mast got bent slightly just above the top tube, and a bit of a dimple formed at the bend. This has turned into a crack. See the pictures below. Any suggestions for how I might get it repaired, if such a fix seems possible at all? I'm thinking that running a weld bead across the crack might actually work, in that it would 1) hold the cracked bit together and 2) fill in the dimple, and thus potentially stop, or at least slow, the buckling that lead to the crack in the first place.

Failing that, are there any suggestions for builders I could persuade to build a new front triangle, using the existing swingarm and links? It's all straight tubes, and the pivot configuration is quite simple.


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## BungedUP (Aug 18, 2003)

If you were interested, I might be able to chop out the seat tube, and weld in a new one. I'd need a photo of the whole thing to get a better sense of it, but that's certainly one possibility. I've removed frame tubes and replaced them on a number of bikes. It's not easy, but it might be easier than replacing the front triangle.

I might be willing to build you a new front triangle as well, if that was your preference.

Feel free to email me:

[email protected]


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## Hardtails Are Better (May 4, 2005)

Email sent. Thanks.


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## thehammertownhead (Jan 23, 2011)

*Side profile of the frame*

I am curious to see what the whole bike looks like......being made of all steel straight tubes and being a DH bike. I always figured most DH bikes were made of aluminum....

Can you post a pic?


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## Hardtails Are Better (May 4, 2005)




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## Walt (Jan 23, 2004)

*Totally fixable*

-Drill the ends of the crack to stop it spreading more.
-Weld the crack shut.
-Put a triangular brace/gusset between the seat tube and toptube that covers the cracked area completely to reinforce (easiest to just cut a triangle out of some rectacular tubing, probably).

Should be as good as new.

-Walt


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## Hardtails Are Better (May 4, 2005)

Thanks Walt. Not sure if I 100% follow where you're intending to put the gusset though. The crack is on the side of the tube, so I'm not sure what you mean by covering it with the gusset.


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## BungedUP (Aug 18, 2003)

The tube is bulged, cracked, and bent - in other words, it has failed to the point that reworking the tube itself is a losing battle, in my opinion. It needs out of there - especially on a DH bike. If it were only a crack caused by some internal high frequency stressor acting on a previous tubing flaw, drilling and welding the crack makes sense (at least to some degree). In this case, the damage is from a crash where the metal hasn't simply fractured from a repeated stress, it has undergone a single high impact event that has caused the tube to be deformed in more than just a tiny localized area. Therefore it should be replaced, as the tube has undergone stress beyond its ability to recover from strain. At least that's my take on it!


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## heeler (Feb 13, 2004)

Thats correct. The area has plastically deformed, so whatever happened exceeded the UTS of the tube... With the defect being so close to the the HAZ of the top tube weld I would recommend a tube replacement. You would want to cut out so much of the defect to get out of the cold worked area that you would get into the TT weld and a good chunk of the ST. That said, you could replace just a portion of the ST (from midway, to the top), if you sleeved the new tube in.

Also, did your seatpost extend into the area where the crack was?


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## BigHank53 (May 19, 2011)

One could also make a hefty external split sleeve out of .058 tubing, cut to follow the curve of the top tube/seat tube junction. Strip off the paint, file down your existing bulge, straighten the seat tube, and silver braze the reinforcing sleeve in place.


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