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Old 11-20-09, 08:48 PM   #1
jk1199
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Cracked alum frame at rear seatpost entry

Hello and thanks in advance. So my problem is this. I have a small crack in the rear of the frame where the seatpost would insert on my 2003 Cervelo Soloist (alum).

I have been reading in this forum about TIG welding as an option but was curious to see what other thought was the best fix. The mechanic at my lbs told me this crack when fixed SHOULD be okay as it doesn't receive an overwhelming amount of stress. Is this accurate at all?

Is this crack worth fixing? I am willing to pay to keep this frame in use if it that's the big factor. Thank you in advance.





My apologies on the low quality pics.
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Old 11-20-09, 08:55 PM   #2
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Are you the original owner of the bike? Because I would certainly try to get it repaired or replaced under warranty.

As for what your LBS mechanic said, it is possible that a repair will hold but it is impossible to tell for sure. Also, the weld will probably be either more or less brittle than the rest of the tube, and that spot needs some flexibility if you will ever be removing or replacing the seatpost.

To recap, try to get it warrantied.
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Old 11-20-09, 08:56 PM   #3
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Have it TIG welded, it should be fine.
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Old 11-20-09, 09:08 PM   #4
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I would go for the warantee. Aluminum has a finite fatigue life. After so many million+ flexes it is going to crack. Check with Tenwheels. Fred's Felt cracked at the seatpost bottom bracket junction. Felt is giving him a new bike.
Aluminum is weldable, but you shouldn't have overstressed it and took it past it's yield if it had proper thickness at that point. They should give you a new frame.
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Old 11-20-09, 09:11 PM   #5
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I bought the bike used so warranty is out of the question unfortunately. I hadn't considered the fact that the weld could effect removing the seat post, now I'm somewhat worried about the weld.

For some additional history. I bought the bike used and the guys at his shop tightened down the seat post collar without the post in it, resulting in the crack he believes. He has offered a full refund or to pay for whatever it takes to fix it. I got the bike for 700$ and don't think I can find another deal like this so I'm very hesitant to return it and would like to fix it if at all possible (on his dime of course). Any other thoughts? Thank you for the responses thus far, much appreciated.

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Old 11-20-09, 09:14 PM   #6
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Originally Posted by jk1199 View Post
I bought the bike used so warranty is out of the question unfortunately. I hadn't considered the fact that the weld could effect removing the seat post, now I'm somewhat worried about the weld.
It could also be cracking in another area on the bike.

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Old 11-20-09, 09:38 PM   #7
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Originally Posted by jk1199 View Post
I bought the bike used so warranty is out of the question unfortunately. I hadn't considered the fact that the weld could effect removing the seat post, now I'm somewhat worried about the weld.

For some additional history. I bought the bike used and the guys at his shop tightened down the seat post collar without the post in it, resulting in the crack he believes. He has offered a full refund or to pay for whatever it takes to fix it. I got the bike for 700$ and don't think I can find another deal like this so I'm very hesitant to return it and would like to fix it if at all possible (on his dime of course). Any other thoughts? Thank you for the responses thus far, much appreciated.
Well I may be wrong but i think that area of the bicycle is a low-stress area, so failure might not be catastrophic(i doubt your seat-stay and part of the seat-tube would shear off). It is a fairly large crack though and will continue to work it's way down the seat-tube, welding may stop it - maybe since there might be a stress fracture that runs down the seat-tube but is not visible to your eye.
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Old 11-21-09, 07:29 AM   #8
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Whats gonna happen is the crack is going to propagate around the welds on the seatstays. Unfortunately, I dont really think welding the crack is going to be a wise idea. The tube may also deform when re-welding and you might not be able to reinsert the seatpost. Not a big deal if the seatpost is round since you can put in a reamer, but you have an aero seatpost which will make post weld machining pretty hard.

Also when taking close up pictures, use the macro function on your camera
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Old 11-21-09, 07:50 AM   #9
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A temporary fix is to drill a small hole, say 3/16", at the bottom of the crack to stop it's progression.
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Old 11-21-09, 02:30 PM   #10
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Get your money back. It is the safest thing at this point.
Drilling a hole (a policeman) may or may not stop the crack from growing.
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Old 11-21-09, 03:12 PM   #11
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Get your money back. It is the safest thing at this point.
Drilling a hole (a policeman) may or may not stop the crack from growing.
Drilling holes at either end of a small crack, then riveting in an aluminum plate, has repaired MANY an aircraft, small and large. So long as the hole is big enough to completely remove stressed metal it should be fine for this application, no?
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Old 11-21-09, 05:47 PM   #12
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Well I have decided to return the frame so it's back to shopping. Please send me a message if anyone stumbles across a 56 Cervelo S1 for sale. Thank you all for you help again, it is most appreciated.
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