I need a different perspective: while washing my bike I found damage to the top tube about 1/3 of the way back from the steering tube. I can't tell if the damage is minor or a serious structural problem sufficient to cause a catastrophic failure. I can't see that the tube is penetrated but the damage seems to extend through the paint into the metal. I know the metal is very thin at this point on the tube. The finish is factory clear coat over aluminum. It looks like something fell on the bike during the winter. I really do not want to buy a new bike or swap the frame.

The mechanics at my lbs couldn't judge the severity of the damage either but assured me that when aluminium fails it does so quickly with ugly results. They sent a picture to Cannondale but I doubt they'll comment on the safety of any damaged frame.

I had to downgrade the picture to meet the forum file size requirement so some of the detail is lost. I should add this is a 63" frame and I'm 6'6" at about 280.

Would you ride it?

My initial opinion - that does not look like a crack. It looks like a scratch resulting in some corrosion / delamination under the clear coat / on to of the bare aluminum surface. Clean it, put some clear urethane over it, and go ride. To play it safe though - have Cannondale look at the pictures and / or get a second opinion.

Frames that fail catastrophically are almost always damaged substantially in the course of an accident. That looks to be about the size of a good thumb nail clipping an i don't think it is as deep as it is wide. There should be an abundance of metal that is structurally unaffected in the area and which experience relatively little stress (compared to about 2" closer). I wouldn't worry. I would keep an eye on it. After a while of not seeing anything change you'll tire of looking at it.

Maybe they would like to sell you a new frame/bike?

Not a fair question, I weigh almost half as much as you do. Would I ride it at your weight? Still yes.

^^^Agree, that this is the most likely outcome here. This is not Cato Fail Carbon we're talking about here. Aluminum will give some warning.

Are you the original owner of the bike? Cannondale may be able to replace the frame.

The middle of the top tube should be stronger than the joints. But, I would worry if there is hidden damage in the frame much larger than the spot you're seeing. Any other places on the frame with those "worm tracks"?

You're in Indiana, so I'd imagine you get limited ocean exposure... but do you also ride that bike in the winter?

As others have mentioned, I'd probably ride it, but also start paying very close attention to it. And, start looking for a new frame to build up with my old components. Or, maybe keep that one as your winter bike, and start hunting for your +1 summer bike.

IMO, it's a scratch/gouge possibly caused by something falling against it as the OP believes, or the (IMO more likely) the bike falling against something. I wouldn't consider it especially severe, especially since it's a way's back on the top tube.

In normal riding the top tube is a compression member so there's more forgiveness than if this were up front on the down tube. The only issue is that it may accelerate local fatigue, though it's anybody's guess by how much.

If it were mine, I'd blend it in a bit with a file and/or emery then clear coat the area. Then I'd ride it as if nothing were wrong, keeping a weather eye for any crack formation. I'm not taking about a close watch, just a glance now and then. Odds are it could last until for years, outlasting your attention span.

That is quite definitely corrosion.

Here is a Cad 10 with serious corrosion issues, and the same kind of spidery wormy look around the corrosion sites.

And, apparently it isn't a warranty issue.

The frames apparently can take a fair amount of abuse after corrosion sets in. However, perhaps you can do something to prevent it from progressing locally. Polish, then reapply clear-coat?

You could have a eddy current inspection done on it. That would detect any cracking from the impact or corrosion.
Cheers,
David in Alaska

I think the clear coat has been opened and a bit of water has seeped in and caused a very minor amount of surface discoloration. This isn't "corrosion" in the sense of deep stuff. It's literally just a small chemical, nearly inert, reaction. I was wondering about the spider webing because it did appear similar to the type of corrosive damage one sometimes finds on painted steel bikes.

OP. Get a bottle of clear nail polish. Clean the area carefully with mild soapy water. Once dry, apply a drop or two of polish to seal the clear coat finish.

I went back to the bike and did what I should have done and finished the frame inspection. It was clean except on the bottom of the top tube. I found more of the same damage including a spot with a similar straight line through it. The spot was slightly soft when I applied pressure with my finger.

There were a number of 'spidery lines' and overall the damage is visually consistent with the CAAD10 that CliffordK linked to (thank you). I couldn't help but notice the CAAD10 appears to have the same Cannondale clear-coat over bare metal finish as my frame.

I'm the original owner; the bike has about 5,000 miles and has always been wiped after rain and stored properly. It seems odd that 4 areas of corrosion would occur on a single tube with none visible elsewhere on the bike.

I posted a couple more pics of the damage on the bottom of the top tube.

I'll mull this over for another day or so but as one poster pointed out there could be more extensive corrosion inside the tube.

Any other thoughts? Can't thank you enough for your thoughts and comments.

Brian

Cosmetic damage is not going to be covered by the manufacturer of any bike after the bike is delivered to the first owner. At this point, I think your best bet is to remove the bubbling/damaged finish and the corroded metal with a file, chemically clean, and protect the newly cleaned metal with clear finish (nail polish). Otherwise, the corrosion process is going to continue under the finish, and eventually do some serious damage to the metal.

unrelated question, but in your second photo, there appears to be a velcro strap going over the shifter cable, is that the case? If it is, not a good idea just from an abrasion point of view.

also, do you put this bike onto a car rack where the bottom of the top tube rests on a rack support, the scratch in the second set of photos makes me suspect this.

I feel that the pix all depict damage to the clear coat, and microscopic, cosmetic at best, damage to the aluminum.
Same thing happens on CF frames with clear coat. Just get the clear coat off with mechanical abrasion (very fine
abrasive only, gently applied) and spray on some new clear coat. Automotive would be fine. Matching the polish
on the underlying aluminum will be difficult but possible, real problem is getting all the striations to line up.

Thanks for all the feedback. To answer questions from djb- You're correct. I should not have the bento box strap routed as it is. I changed that and will be removing it more frequently to clean under it (on this and future frames). It sometimes sits on car rack but usually I ride from my home.

The damage does seem to extend into the metal to at least a small degree. I'll try some cleanup with fine sand paper or a file and get a better look a the penetration (if any) and make a decision on whether I'll be comfortable riding it on fast descents.

I can't thank you guys enough for the discussion.

Brian

being more of a tourer type, with bikes with racks and whatnot, on frame areas where contact can occur with stuff, I've often put some electric tape or hockey tape just so the paint doesnt get rubbed off and or abrasions. Electric tape stays on reasonably well and you usually can put it on discreetly just on the abrasion point and its easy to take off too.

but thats good that you have changed the setup, the cables would definitely be rubbing against the frame all the time.