Bicycle Mechanics - Will this dent on an aluminum frame make a difference?

Hi-

I recently have come across a great deal on a Cannondale Optimo frameset, but it has a noticeable ding in the top tube. I know it's hard without seeing it in person, but do you guys think that this will compromise the structural integrity of the bike? The tube is still straight.

http://farm4.static.flickr.com/3332/3249208138_711a851db0_o.jpg

It's far enough away from the wields, I'd still bring it into a lbs to get an opinion though.

I wouldn't want it.

Aluminum is brittle, it probably got that dent in an accident so who knows what cracks are hidden in that frame waiting to catastrophically fail?

Besides, tubes get their strength from being round, that dent makes a weak point right in the middle. Great place for the frame to buckle.

It doesn't look that bad, but a closer shot would shed more light. Heck look at the chainstays degree of crimpage.

Dented top tube is not good because it is under compression. You probably heard this before about compressing an empty coke can, then try it again with a dent on the side of the can. Anyway, I wouldn't ride it.

Any dent is a stress concentrator.

Example - take a clothes hanger and bend it back and forth - notice that the bend is spread along the whole length being bent.

Now take a hammer and put a dent in the wire and bend again. Note that the bend is now all concentrated at the dent.

Metal fatigue will eventually make it fail at that point.

How long? Who knows? But, it will be faster than without the dent..

It's a great deal becuae the owner knows no one will pay the going price with that dent.

Who knows. The dent might not cause problems or it could cause the frame to buckle on a high speed descent after hitting a hole. I wouldn't take a chance.

Dude, on the one hand, you're thinking about buying a frame that was the "lightest" http://outside.away.com/outside/gear/200403/road_bike_review_2.html frame made of a house brand alloy by a company that's been nicknamed "crack'n'fail, and you're wondering if you should be concerned about a ding in the top tube?

On the other hand, $80 on craigslist IS a hell of a deal.

I'd compromise. Buy it, but build it up as a fun lightweight fixie for riding around town, rather than as a serious road bike.

Not worth it. For any application where you'd notice a difference between that frame and a cheaper one (ie, hauling ass), you wouldn't feel safe using it.

I don't like riding while second-guessing my hardware.

Riders have been ridding bikes with dented top tubes for decades. Heck, how manufacturers cut holes in top tubes to run cables through?

So, what everyone here is saying is that if they crashed their own bike and the crash resulted in an identicle dent that they'd part out the frame?

I dont think so.

So, what everyone here is saying is that if they crashed their own bike and the crash resulted in an identicle dent that they'd part out the frame?

I dont think so.


I know I would. After I called Cannondale to see if they had a crash program.

I wouldn't worry abut it. I've raced on far worse damaged frames.

I bought a Cannondale on Ebay with a ding about that size and I haven't looked back. For $80 I'd go for it.

I had the same caad5 frame with the same dent in the same place. It was 10 years old when I was riding it, and it's still being ridden. It'll be fine. People are riding dented c'dales all over the place, it's thin tubing and it dings. I've never heard of it failing on a pothole in a high speed descent, or whatever. $80? Go for it. It's a pretty frame too.

So, what everyone here is saying is that if they crashed their own bike and the crash resulted in an identicle dent that they'd part out the frame?

I dont think so.

If its aluminum, Yeah I'd part it out.

Good thing I only ride Steel.

I have a dent about like that one on my Trek Fuel. It gets about 1000 miles of cross country riding every year including two endurance events. I dented it in a race three seasons ago. Naturally, I worried about the very issues brought up here and still do. Trek has been great to me as far as warranty on this frame in the past but I know if it fails anywhere near that dent, I SOL. I ride it and have had no troubles yet - and I'm a Clyde and known to put hardware to the test.

"Will this dent on an aluminum frame make a difference?"

It already has. You're concerned enough about it to start this thread. I doubt you'd enjoy owning it.

Ride it ----- I seriously do not think it will be an issue. If I dinged one of my bikes like that I would still be riding it as would anyone else. Lp