If the bike was subjected to a front end crash, as has been plausibly suggested, the wheel would obviously take the initial impact, which would then be transferred to the fork, then to the frame. Neither of these forces would necessarily result in a visible crack, or scratch.



Because that lump isn't normal. Other guys with the same bike report no similar lump. I pointed out that you can clearly see that the tube edges are at differing angles, and intersect at that lump, implying a bend at that point.


That's because there probably isn't a crack, but a ripple in the tube material. But at some point, I'd say it's likely the paint will fail to adhere and will begin to flake off at that area.

A lack of scratches doesn't mean that there's no structural damage. It's not surprising that the fork blades would still look normal, they've likely got a much higher yield strength than the frame. But it's hard to know by sight that the overall fork (including the steerer) is actually safe, and the stakes are high: that's a seriously deadly spot for a bicycle to fail.

Because it's shaped in a way that it shouldn't be, and which is typical of front-end collision damage. This is what my Emonda ALR frame looks like:



The ripple on your bike is definitely not a weld. The weld at the regular headtube junction is very obvious, and there's no reason for Trek to have built your downtube in two pieces.

I think one of my comments may have misled you (that is, I was wrong). Significant structural issues can be hidden by paint, and a deformation of the frame may not disrupt the paint surface. My thinking has changed to where I tend to suspect that there was a bonk to the frame and it put this slight ripple in the frame. And it may have damaged the fork underneath the paint.

I think I'm going back to what I and a lot of others have said: check with Trek.

You can supply them with more info if you get the exact axle to axle dimension ("J") in addition to your pictures.

This is the part you can't know unless you have very specific and expensive testing performed, and even then it's not always clear. A carbon fork isn't going to be bent or show visual indication that the underlying fiber matrix has been damaged. In other industries carbon fiber parts will be removed from service not because they are visually damaged or show damage on test scans - they are pulled because they have been exposed to a level of force exceeding the safe standards for that part. Damage to the downtube from a front end impact would be one such reason.

The frame is damaged because it has a visual indication of a significant front end impact.

Post 27 shows all you need to know. Your frame has a crease, ripple, dingleberry or whatever where it shouldn't. Get your money back, move on.

I wish I could but unfortunately, the person who sold me the bike is not accepting a return.

I have contacted Trek but they said that they can't assist me as I am not the original owner. I will try to go to a Trek reseller to get their opinion on the safety of the frame but I am not sure it will be much different from what many people already said in this forum.

Thank you very much for this! As many posts suggested my frame is damaged. Now the challenge will be to judge whether it is safe to ride or not.

If its eBay you can force a return if the item is damaged and the seller didn't tell you. In fact, if the item is damaged and the seller didn't tell you, you could probably force the issue wrt this being fraud. May not be worth it.

Check the "J" dimension. Check the fork for flex and for any grating sounds.

It's difficult to receive a useful answer to a black-or-white question. Maybe ask "to what degree is it unsafe?" And the answer is something like "it depends..."

It's a tube that failed (partly) in buckling - the result of a lengthwise force that exceeded the capacity of the tube. Like when you press leghtwise on a bathroom paper tube. Trek's Alpha 300 Aluminum is effectively 6061 T6, the T6 part describing the thermal treatment. It does not take plastic deformation well - 6061 is formed in annealed state, then heat-treated, because after heat treatment it gets a lot stiffer but also a lot more brittle and a lot less tolerant to plastic deformation. Long story short - I wouldn't ride it. Unless you already lost all you teeth. I'd certainly use it on a trainer, however.

And since we agree it was crashed, the next logical question is - how. Car door. How do I know? Been there, done that, got the frame bend. No scratches on the frame.

I understand why you wouldn't ride it but could you let me understand a bit more what is the risk? Are we talking about a sudden failure of the frame while riding? If so, could I do anything to anticipate it or it could already happen on the next ride? Sorry to bother you with questions but I have spent some money on this bike so before throwing it in the bin I would really like to understand the situation. Thanks in advance.

Asking to know when and how it will fail is asking the impossible, as is how badly you will be hurt when it does fail. If I were to tell you "it will be OK if you ride gently and only split like a beer can if you hit a pothole," why would you put your trust in some random poster on the internet? It's not fun when you've been cheated out of hard earned cash, but it happens. The only responsible action now is to cut the thing up, recycle if possible. Sorry.

I understand and I am willing to accept that the only answer could be that it is impossible to know. Just looking for some knowledgeable people

translated ....aluminum in this frame when bent (plastic deformation) gets more brittle and can fail completely with no warning. The bulges are weakened failure points right now. There is no guaranteed way to see it getting worse or predict when or if it will fail, but the failure will not be gradual...it will be all at once

the result if it were to happen at speed would be painful

it could ride for years or it could go next ride

So you need to balance How much health insurance do you have and how tolerant to pain are you vs what will it cost to strip the components and find a new frame/fork to put them on

So

J dimension is correct

While aluminum frames are less resistant to impact damage than some other materials, I think if this were my bike and my choices were either to ride it or eat it, I'd ride it. Here are my reasons:
1) The fork appears undamaged. (Devil's Advocate mode: a damaged fork could have been replaced.)
2) The "ripple" is somewhat remote from the head tube; I've seen frames damaged by frontal crashes and the wrinkling is usually closer to the head tube.
3) There appears not to be a similar wrinkle in the top tube; I'd expect some damage to both tubes, though I agree this might not happen.
4) The wrinkle is in an easily inspected location. This is the main reason I'd ride it. If the frame began to crack, it would be detectable by running a finger over it. The tube wouldn't go from its present condition to total catastrophic failure in an instant. Even if it did, hypothetically speaking, there would still be the top tube holding the bike together.
That is my $0.25.


Frontal impact damage

Do you think it would be worth it to remove the paint and inspect the aluminium for cracks? I guess it could be a better option than throwing it directly in the bin.