Hi,
Newish caad10 here, no more than 2000 miles or so.

I noticed this small "blemish" while cleaning. It concerned me. I took it to my LBS, which I trust very much. They are well known and reputable here in the area. Their mechanic took a look at it, and said it doesn't look too scary. He said he would take some photos of it just in case, and in the future we can compare to see if the area in question has changed. Nonetheless, I'd like a second (or third, fourth, ...) opinion.

The bike has never been "seriously" dropped, except that one time off of my car from one of those horribly low over-hangs last summer. LBS said I was lucky that it didn't do any serious damage except damaged by front fork (which we replaced). They did a full inspection and said it was alright.

Fast forward to the present time, I see this crack and it concerns me a little. I'm not sure if it's related to last summer. Bike isn't making any noises and rides fine. The last thing I want is an aluminum frame failure while hauling around a corner or down a mountain.

Thoughts? See photos below.



High Res on Imgur
Imgur: Photo 1
Imgur: Photo 2

Could be a crack, could be nothing. You can't tell with the naked eye, so I certainly can't tell from a photo.

You could use a dye process to bring it out, or polish the area and see if it polishes out (not a crack).

There are various way to use dyes to verify cracks. If you don't want to spend on special dyes and developers, go to the stationers and buy a bottle of india ink (or fountain pen ink at the antique stationers). apply the ink, give it a moment to penetrate and wipe off excess. Not press newsprint, blotter paper or even a paper towel hard against the crack. The amount of ink it pulls out is an indicator of the depth and size of the crack.

I'll add that unless the possible "crack' is in an area that has a catastrophic failure mode (as in loss of control/total structural failure) few companies will deal with the concern until actual failure happens. The failure mode for a REAR drop out break isn't in that category. Andy.

I guess my concern was catastrophic failure. So even if it "is" a crack, its not likely to be a huge blow out? This makes me feel a little better. I love the bike. I was about to throw some nice new wheels on it, but if the frame needs replacing, I'd rather use that money for a new one. Maybe I should just see if it grows over the next few months, and go with some new wheels

Perhaps not catastrophic, but depending on where it happens it could mean a long walk home.

Yes, but there's some protection available against even this.

The OP can mark the end of the crack, and observe if it spreads. Odds greatly favor, no sudden failure before noticeable growth on the crack.

If this is a metal frame,there might be a weep hole on the back side of the chainstay....Use compressed air in the weep hole and soapy water on the crack.....if you see bubbles......not good.

You may have to pull the bottom bracket out to put the air in the tube from there or plug it if it has a weep hole.

Die check works but it has to be clean (as in no paint) for it to work well.You can get false readings from penetrent getting under paint edges.

I'd keep a CLOSE eye on it every time I mounted and dismounted. If that thing comes unglued when you are at speed in a turn......it'll be ugly.

One method I use on suspected cracks is to "paint" it with some nail polish. If it cracks in the same place as the suspect crack, you have a crack. How you deal with it is up to you.

It looks to me from the light hitting the edges, just chipping of the clear coat. CAADs with bare ALU are clear coated to protect the finish.