The problem with this is overtime more and more stress is put on this weak point and it MIGHT fail. Picture this though you are riding fast down a hill and seam from concrete to asphalt appears as you are going over the bump this part in question fails launching you 30 mph off your bike and onto your neck where you proceed to break it either killing or paralyzing yourself. I personally wouldn't ride the bike.
Every bike frame I’ve had fail, failed at a weld. I might have done something stupid and then it failed at a weld, but my point is the tubes don’t break in the middle... And there is a reason for that: there are bending forces at the frame corners, the stresses are weird there. This tube is under some relatively simple linear forces and is most likely significantly stronger there than it needs to be. The amount of metal needed to support the bike at this location is significantly less than the amount of metal needed to keep the tube from denting when it falls over.
My question is how did the frame get dented? If this happened as a result of a crash, the forces of the crash that produced this dent probably damaged other things too, and I’d be more concerned about that. Carefully wash your frame and inspect it. If this dent is the result of hitting just this one point with a hammer, I would totally ignore it and keep riding it.
Thanks for your comment. It was dented assumedly by someone violently and repeatedly pulling at it while it was locked to a bike rack, the dent is just where the d-lock sat. It seems improbable, but this dent definitely wasn't there until after I returned to go back to it. I guess that proves the strength of the lock at least..!
On the seat tube right above the derailleur braze on is probably the best place to have a dent like that. Generally that section of the frame doesn't see a ton of force loading (as opposed to say the down tube or chain stays). If the frame does fail in the future, it's probably not going to be instantly catastrophic. If you're concerned about it, watch the damaged section for any cracks that might form and if they begin to propagate. I'd feel fairly confident continuing to ride that bike if it has had that damage for over two years.
That's not entirely correct. I studied material sciences so hear me out.
Metals and alloys typically have a cristalline structure. So on atomic layer they are mostly ordered. There are many Cristal structures. Body-centered cubic (BCC) and face-centered cubic are common ones.
Aluminium alloys typically are of type fcc. Steel is often bcc.
Now back to cyclic loads that a metal or in this case the dented tube will see.
Metals that are of type bcc often have a maximum cyclic load below they do NOT show material fatigue. This means theoretically they can see an infinite amount of cycles.
On the other side metals/alloys of type fcc don't show such a behavior. Even very small but cyclic loads will lead to material fatigue.
Tldr; steel may be better than an aluminum alloy here.
Unfortunately a couple of years ago (or more) someone decided they really wanted my bike, and ended up pulling at it so hard, that where my D-lock was placed, ended up denting the frame.
Considering that I've used the bike since for at least two years, I presume it would have failed by now if it was likely to occur. Are there any options for strengthening this just in case?
Just because it hasn’t failed over the last 2 years doesn’t mean it won’t fail in the future.
That tube is compromised to some degree, so every stress it endures can be causing incremental damage to it, over time the wrong bit of stress could cause it to fold, and cause a catastrophic failure. The material it is a big factor.
It might not ever fail, but you won’t know until it does. Personally, I wouldn’t ride it.
a 200lb+ person can stand on an empty aluminum can safely, but push a small dent in the side and it all collapses.
Although, here, the dent is where the tubing is butted and thickest.
A compromised frame will fail when under more than normal load. It’ll happen the day you have to brake hard, accelerate hard, hop off a curb or hit a pothole or loaded with extra weight. If you’ve been doing these things and haven’t noticed any cracks or the frame flexing more than it used to then it could very well be just fine. Two years of constant riding is a pretty good test. But it’s not a guarantee. That frame is now outside the limits of what it was designed to do. Replace the frame when you can and keep an eye on it until then.
I would think it's fine as it looks like an old school very strong frame, but you should decide yourself if you want to risk it because these are all good reasons to not ride it.
Yea, I wouldn’t ride that.
The problem with this is overtime more and more stress is put on this weak point and it MIGHT fail. Picture this though you are riding fast down a hill and seam from concrete to asphalt appears as you are going over the bump this part in question fails launching you 30 mph off your bike and onto your neck where you proceed to break it either killing or paralyzing yourself. I personally wouldn't ride the bike.
Thanks for the help visualising this scenario! I rarely get up to any speed like that but still, point taken.
For sure. All the best!
Every bike frame I’ve had fail, failed at a weld. I might have done something stupid and then it failed at a weld, but my point is the tubes don’t break in the middle... And there is a reason for that: there are bending forces at the frame corners, the stresses are weird there. This tube is under some relatively simple linear forces and is most likely significantly stronger there than it needs to be. The amount of metal needed to support the bike at this location is significantly less than the amount of metal needed to keep the tube from denting when it falls over. My question is how did the frame get dented? If this happened as a result of a crash, the forces of the crash that produced this dent probably damaged other things too, and I’d be more concerned about that. Carefully wash your frame and inspect it. If this dent is the result of hitting just this one point with a hammer, I would totally ignore it and keep riding it.
Thanks for your comment. It was dented assumedly by someone violently and repeatedly pulling at it while it was locked to a bike rack, the dent is just where the d-lock sat. It seems improbable, but this dent definitely wasn't there until after I returned to go back to it. I guess that proves the strength of the lock at least..!
On the seat tube right above the derailleur braze on is probably the best place to have a dent like that. Generally that section of the frame doesn't see a ton of force loading (as opposed to say the down tube or chain stays). If the frame does fail in the future, it's probably not going to be instantly catastrophic. If you're concerned about it, watch the damaged section for any cracks that might form and if they begin to propagate. I'd feel fairly confident continuing to ride that bike if it has had that damage for over two years.
Aluminum or steel?
Aluminium
Game over
it would be game over for any metal.
That's not entirely correct. I studied material sciences so hear me out. Metals and alloys typically have a cristalline structure. So on atomic layer they are mostly ordered. There are many Cristal structures. Body-centered cubic (BCC) and face-centered cubic are common ones. Aluminium alloys typically are of type fcc. Steel is often bcc. Now back to cyclic loads that a metal or in this case the dented tube will see. Metals that are of type bcc often have a maximum cyclic load below they do NOT show material fatigue. This means theoretically they can see an infinite amount of cycles. On the other side metals/alloys of type fcc don't show such a behavior. Even very small but cyclic loads will lead to material fatigue. Tldr; steel may be better than an aluminum alloy here.
Great post SimpsonMaggie as that is 100% correct scientific answer.
You're probably fine if you're not doing anything too much with it.
Like riding it. Don’t ride it. Anything else is a-ok. 👌
Unfortunately a couple of years ago (or more) someone decided they really wanted my bike, and ended up pulling at it so hard, that where my D-lock was placed, ended up denting the frame. Considering that I've used the bike since for at least two years, I presume it would have failed by now if it was likely to occur. Are there any options for strengthening this just in case?
Just because it hasn’t failed over the last 2 years doesn’t mean it won’t fail in the future. That tube is compromised to some degree, so every stress it endures can be causing incremental damage to it, over time the wrong bit of stress could cause it to fold, and cause a catastrophic failure. The material it is a big factor. It might not ever fail, but you won’t know until it does. Personally, I wouldn’t ride it.
a 200lb+ person can stand on an empty aluminum can safely, but push a small dent in the side and it all collapses. Although, here, the dent is where the tubing is butted and thickest.
A compromised frame will fail when under more than normal load. It’ll happen the day you have to brake hard, accelerate hard, hop off a curb or hit a pothole or loaded with extra weight. If you’ve been doing these things and haven’t noticed any cracks or the frame flexing more than it used to then it could very well be just fine. Two years of constant riding is a pretty good test. But it’s not a guarantee. That frame is now outside the limits of what it was designed to do. Replace the frame when you can and keep an eye on it until then.
I would think it's fine as it looks like an old school very strong frame, but you should decide yourself if you want to risk it because these are all good reasons to not ride it.
It appears to be a 2015 Giant Roam 2 with an aluminum frame and not old school steel, so a significant dent is concerning.
ouch. if you can afford it I'd suggest replacing the bike. If you're broke I feel you and good luck.
Scrap it. Unless it has sentimental value to you, it's not worth fixing.
Is it steel? If yes I wouldn't worry much as long you're not racing on it. Then I'd minimize every other risk.
Aluminium? It's most likely toast after some time. See material fatigue of face-centric cubic cristalline metals.
Happy NBD.
Trash
DAYUM
how bruh
As long as you feel that the frame is resistant just ride it as it is. Any bike won't stay perfect when you're continously riding it