General Cycling Discussion - Dent on bottom tube. How can I fix or repair it?
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07-25-10, 09:35 PM
Today, while carrying my two bikes in bed of my truck, one bike fell on top of the othe bike. Bottom ride lower tube has a huge dent about size of a nickel. Any good idea on repairing or fixing the dent? I'm lost and have to idea on how to get the dent out. Any suggestions will be greatly appreciated. Thank you.:(
07-25-10, 09:42 PM
It would help to know what material your bike is made out of as the approach to fix it would be different with steel vs aluminum.
07-26-10, 12:27 AM
Specialized Langster. Alumunium frame.
07-26-10, 04:06 AM
I was afraid you'd say that, aluminum frames are unique beasts in that they are heat treated to relieve any stress cause during welding. Assuming of course your frame is welded. It may be a bonded frame which it might be easier to repair. Either way your going to need to find a competent repair shop to do the work, and it won't be cheap to have it done as your frame will more than likely need to come apart. After which it would need to be reheat treated if it's welded. The only other thing I can think of would be to drill a small hole in the bottom shell into the down tube and push out the dent from inside the tube. But even that is a lot of work, how bad does the dent bother you? Does it affect the overall stiffness or ride quality of the frame? Is your bike still safe to ride?
BTW I'm not a frame builder I'm just a guy who happens to do metal work as a hobby. I'm sure there are other people on here that are much more capable than I at helping you with your problem.
07-26-10, 10:20 AM
I took the bike out last night after the dent incident. I can't feel anything different with the ride. I think it should be safe to ride. I will keep an eye on it once a week. I think it's a great idea regarding drilling a little hole underneath the bottom tube to push the dent out. I will try to take it to a bike shop this weekend to have them evaluate the dent. I think it just a cosmetic issue for now. It's so hard to deal with something like that. :( Thank you for your help.
07-26-10, 01:28 PM
As the other post said, aluminum is hard to bend back. If it were steel, any competent shop could probably fix you up with a "frame block," a sort of clamshell tool that you clamp over the dent and rotate to squeeze the frame back into shape (http://www.bicycletool.com/frameblock1.aspx). You don't mention the size of the dent-if it's small, it could be harmless, but I don't really have much experience with alum frames.
FWIW, I'd be leery of drilling holes in aluminum. It might be OK, but I don't trust the material that far.
07-26-10, 08:00 PM
If the dent is not affecting the bike, I'd leave it alone. Also, I wouldn't drill a hole in the down tube as it's quite thin (I.E. why it dented in the first place) I was talking about removing the cranks and bb and drilling a hole thru the bb shell into the void of the down tube where they attach to one an other, and pushing it out that way. The bb shell is much thicker than the thin down tube and I wouldn't think it would have a negative affect on it. But if at all possible I'd live with the dent.
07-26-10, 08:42 PM
If the dent is not affecting the bike, I'd leave it alone. ... The bb shell is much thicker than the thin down tube and I wouldn't think it would have a negative affect on it. But if at all possible I'd live with the dent.
Good advice, IMO. But a SMALL hole in the BB shell might not be a problem. My first couple of mountain bikes, back in the '80s, had them for drainage, because we used to do a lot of water crossings. But they were steel, not aluminum..
07-26-10, 09:56 PM
can you post some pics? I agree with the leave it alone crowd
07-26-10, 10:35 PM
I agree, leave it alone.
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