ridelikeaturtle

I'm cleaning a friends bike, an aluminum Trek frame. She was in a serious crash last year, apparently hit from behind by a car (I didn't know her then), and since then she's had the bike into a local shop where she said amazingly there was only 30 euro worth of damage done to it (whereas she was in the hospital w/a 10hr surgery and titanium plates in her shoulder, multiple fractures, etc.).

Anyway... she hasn't ridden since then, but is now recovered and is looking to get back onto the bike, and wanted me to give it a clean and a once-over. I rode it for a short distance (just standing on the pedals), something didn't "feel right" to me, though I put that down to the fact I'm 6'1" and it's a 50cm frame, with a tiny stem, female-specific geometry, and is a bit top-heavy as she's got stuff all over it (saddle bag, frame pump, etc).

If there was something wrong with it, I'd have expected the shop to find it. But you never know.

It looks to be in fine shape, quite clean even (compared to most bikes friends drop in to me to go through). But the #1 thing I always do is clean clean clean and try to reveal anything odd... and here's what I've found:










Do any of you have experience with similar "could be just an ugly scratch" on an aluminum frame, on the downtube near the BB? You can feel it with your fingernail.

Also, does anyone have experience with Trek's warranty / customer service? She probably still has a record of the purchase (via CC or similar), I don't think the bike is more than a couple years old.

I'm aware when aluminum "goes", there's no warnings (unlike steel).

I'm going to suggest she drop it in to another shop that I trust, for a second opinion. She's (reasonably) going to be a bit nervous getting out on the road again.

Thanks in advance for any opinions, thoughts, and info!

ridelikeaturtle

On second look at the posted photos, it really does look like a crack.

CargoDane

If she was in a crash there is no way the warranty will cover anything at all.

To me, when I click on the pictures and enlarge, it does only look like scratches, but in order to check if it just is such a thing, I don't see any way other than to sand it down to see if you can remove it. If it's impossible to get to the "bottom of the scratch", it is not a scratch, but a fracture.

ridelikeaturtle

I don't suppose there's an ultrasound test or similar that'd work on an aluminum frame (like for carbon)?

Skulking

If you really want a definitive answer, you can always try and find someone who does Non Destructive Testing (NDT) and have them check it probably with either X-Ray or Ultrasound. Typically something like that would be used for a more industrial purpose like checking weld penetration on a critical part. I'm not sure if you would actually be able to find someone to do it for a bike frame. Something like that is really the only way to be absolutely certain though.

CargoDane

You could x-ray the frame, but do you really want to do that?

What makes me think it's scratches is the way the paint is chipped along the lines, but also the fact that it is only on the non-drive side where something could hit (an spd-shoe with a sharp edge or something like that). It is way cheaper and easier than X-ray to sand it down to check.

phughes

To me, they look to be scratches. You could sand the area down to see, but I really do not think they are cracks.

Davespix

From these pictures it does look like the paint is scratched not cracked since the edges of the paint are pushed In rather than cracked from below. To be sure I’d sand it with 320 or 400 grit sandpaper Then repaint or put a sticker over it.

davidad

It can be dye checked but the paint would need to be removed. Once the paint is sanded off the crack would show regardless.

Iride01 

Find a firmly mounted vice or place to clamp the other end of the tube. Wrap with a big piece of something to protect the finish. Grab the chainstay and top of seat tube and put some bending and torsional stress on it. If it doesn't open up, it's just a scratch.

I have trouble imagining a scratch running like that, but I can't imagine a crack running like that either, especially where it goes through the weld.

I lean toward it being a scratch.

Trying to find someone to do other types of non-destructive testing will be next to impossible. And, it'll cost more than is worth being spent on a bike.


edit..... You have rubbed on it and tried to clean it haven't you? Looking back the second time it looks suspiciously like threads of tire sealant that sometime get on my bike and stick a little before coming off.

ridelikeaturtle

Yep, I've cleaned it up a bit (matte black shows any kind of dust), I was hoping it was something like residue or road grime; but yeah I'm also leaning towards scratch, not crack.

But I'm still going to suggest visiting a higher-end shop if there's any doubts, if for no other reason than to have a more experienced mechanic put a second pair of eyes on it.

dedhed

Looks like a scratch. Especially as it involves the weld as well as the tube. Cracks would tend to follow the weld and not meander like that one. A little fine emery cloth, clean it up for a better look, and see if it is surface or through, touch up the paint..

Amt0571

The shape suggests me it's a scratch.

Litespud

The upper one looks like a scratch to me. The one shown at the BB could be either - however, the fact that it meanders across tube and weld without any obvious difference suggests to me that is is also a scratch. If the frame had been torqued sufficiently to cause a crack, I might have expected the crack to behave differently as it traversed different materials, thicknesses, etc - maybe run along a weld, for example. However, all this is purely speculative and worth the pixels it’s printed on.
If this were my bike, I’d get to the bottom of it - literally and figuratively - by sanding down the paint to bare metal and determining definitively what you’re dealing with. If a crack, investigate a repair or suck up the cost of a new frame. If a scratch, fill in the divot and respray the area. If it matches, great, if not, no matter. It’s a battle scar. God knows your friend is likely to have a few (and hats off to her for wanting to get back out on the bike). Absolutely nothing wrong with her bike having a few scars.

Geepig

To me it looks like something hit that, maybe during the accident, enough to damage the paint and outer surface of the metal.
If you have some bikes available, you could try tapping the area on this frame and in the same place on other frames and listening to the sound it makes. I have never attempted it on a bike frame, but just like a musical instruments any slight defect can change a bright sound into one with a duller note.

Mista Sparkle

I was going to suggest something along these lines. Another vote for scratch.

Plus, you can see metal below, it kinda looks like paint was scratched as a crack would likely look a bit more closed up.

Looks like the many things I have accidentally scratched with a frayed piece of wire rope.

dedhed

1saxman

Looks like a scratch or possibly like a hair of fiber under the paint. I wouldn't do anything to it.

CargoDane

LOL, you need to click through on the pictures (two clicks). It's not a hair or fiber under the paint. The paint is gone. It looks like a scratch the way the paint has peeled off.

Moe Zhoost

Looks like a scratch to me. I don't think a crack in Al would propagate that way.

Rolla

Scratch, based on the squiggly shape and how it crosses the weld. Looks more like someone scraped it with a tool or another bike's pedal.

1saxman

LOL! It was merely a suggestion - we're not voting here on what it could be and there will be no winner. You see what you want and I'll see what I want.

CargoDane

Yes, but have you clicked on the photos to have a closer look? There's a (slight) chance it's a crack, a bigger chance it's scratches, but no chance it is a hair or fibre caught under the paint as the paint is not there.