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Old 02-24-07, 10:42 AM   #1
catalyst
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Can you get rid of a dent in aluminum? (pictures)

I just got a Bianchi Pista Concept frame and there is a good sized dent 3/4 the way up on the oversized down tube about the size of a quarter. Is their anything that I can do to remove the dent. Will the dent cause significant structural damage to the bike? Should I worry about the frame cracking?

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Old 02-24-07, 11:36 AM   #2
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Quote:
Originally Posted by catalyst
Should I worry about the frame cracking?
It already started to crack, DON'T RIDE THIS.
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Old 02-24-07, 11:37 AM   #3
catalyst
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that's the paint.
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Old 02-24-07, 12:14 PM   #4
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Put a sticker over top of it, maybe a properly sized Mavic one would look cool. Yeah, that's just paint cracks. Put some clear nail polish over it to prevent it from flaking.
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Old 02-24-07, 02:47 PM   #5
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1- Stating the obvious, the tubing wall thickness is thinnest in the area of your frames damage. Triple butted tubing has (3) different wall thicknesses, ends are both thicker. Double butted tubing is the same on each end, thinnest away from ends.

2- The only way to tell if the tube has any cracking is to remove paint in that area and do liquid penetrant testing. This is done at the factory, by a certified tech., on every piece of tube. Its standard QC procedure.

3-High tensile Al tubing is formed then heat treated to reach specific properties. When this material is deformed i/e stressed beyond its yield point, the crystal lattice is disturbed. This is bad, stresses are concentrated and very small cracks can grow quickly, usually at the worst possible moment.

Check with Bianchi USA or a dealer to see if they will test the frame for you. It may take a few calls but they have an interest in having you ride a safe bike. Light, Hi Tech equipment is great for all of us, but we have to deal with more complex issues.
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Old 02-24-07, 03:48 PM   #6
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Short answer - aluminum usually stretches when deformed so you can't usually repair it cosmetically. The fact it got whacked hard enough to crack the paint finish is a bit disturbing. I'd guess trying to fill it and paint over it would be rather expensive.
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Old 02-24-07, 06:24 PM   #7
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Check the frame for straightness. If it took a hit hard enough to ding the down tube to that extent, you could have a bent frame.
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Old 02-25-07, 12:26 PM   #8
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Some good paintless dent removal guys who work on high-end exotic cars (Ferrari's are aluminum) can minimize the dent. We had a customer with a ding in his beautiful Project 1 Klein who took it to such a specialist and for about $80 had it looking as good as new.
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Old 02-26-07, 03:05 AM   #9
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I went and got the ding king. It work pretty well. I pulled it up by hand instead of using the brace. I don't care about the paint, it's getting powder coated.

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Old 02-26-07, 03:22 AM   #10
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Off topic here, but still a great little anecdote.

A little while back one of the students drove into the back of the automotive teachers truck with a peice of square stock hanging out of there own truck, the teacher didnt care about the scratch but it was up to the students to get the dent out. We tried the toilet plunger method but it did nothing, so we ordered up a similar dent pulling tool, it stuck better and seemed it would work, but nobody in the class had the strength to pull it.

So, we sat around and then came up with the idea any bunch of ********, redneck teens would come up with. We tied it to a truck. Yes, we are that dumb. Yes, the dent did get pulled. Yes, we did break a window.
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Old 02-26-07, 10:26 AM   #11
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Quote:
Originally Posted by seely
Some good paintless dent removal guys who work on high-end exotic cars (Ferrari's are aluminum) can minimize the dent. We had a customer with a ding in his beautiful Project 1 Klein who took it to such a specialist and for about $80 had it looking as good as new.
Just because you pull out the dent doesn't mean the strength of an Aluminum frame isn't compromised. This is less true with steel...and the sheetmetal on cars is not a critical load bearing component.
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Old 02-26-07, 10:47 AM   #12
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isn't pulling the dent just further weakening the area?
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Old 02-26-07, 06:00 PM   #13
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Quote:
Originally Posted by iNewton
It already started to crack, DON'T RIDE THIS.
The first one is still the best.
Aluminum fails explosively (see post in FG/SS forum regarding Nitto bars)

Enjoy
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Old 02-27-07, 11:06 AM   #14
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Some frame builder used to use pressurized oil in a tube to pop out dents in steel frames. Not sure if this guy is still around. Worked great on steel. This was 15+ years ago.

For aluminum - I'd consider the frame disposable and relegate it to trainer work, grass bike handling practice, etc.

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Old 02-27-07, 03:13 PM   #15
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Quote:
Originally Posted by jemoryl
Just because you pull out the dent doesn't mean the strength of an Aluminum frame isn't compromised. This is less true with steel...and the sheetmetal on cars is not a critical load bearing component.
Actually, pulling out the dent made the alu around the area even weaker. I work with steel and alu metal professionally, and I can tell you this : aluminium has very little elasticity and a low fatigue tolerance. When a metal tube is dented, it means the metal at the dent spot has gone over the elasticity limit and into the plasticity zone. With steel, it weakens the metal a bit (meaning it has a little less fatigue life left in it) but steel is plastic and resilient, so it can be bent back and is still good. Bent alu however is weakened considerably, and the metal that got "cold formed" like this is as good as dead for mechanical stress-bearing applications. When the dent is pulled out, it just makes the problem worse.

The short answer is this: I'm not sure where the metal was bent exactly, but it would have been better left alone and not "fixed". Depending on the tube wall thickness, the weight of the rider, the exact area where the dent occured and the weight of the rider, the bike may or may not be safe. I certainly wouldn't ride it.
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