Thulsadoom

My trusty 520. I haven't had a load on the front in years and yet this is what I found today after my ride. It just seems like a strange place for a crack---the lower tube right at and into the head tube.

rccardr 

Odd place, yes. Not a new crack, tho- looks like plenty of corrosion in the cracked area.

grumpus

Probably started as a weld defect, I wonder if there was a previous repair or crash damage.

alcjphil

Actually, that is a high stress area. A crack there isn't surprising. It shouldn't happen, but if that is a butted tube, the crack might be where the butting ends

Bill Kapaun

Is the fork bent as if someone ran into a wall?

grumpus

If the butting is that close to the end then someone used the wrong tube, or trimmed it in the wrong place.

FBinNY 

It seems to be a welded aluminum frame. If so I'd consider it a defect and file a warranty claim.

As to the cause, possibly there was a defect in the tube itself. Or, unrelieved stress from a poorly aligned joint, (depending on weld sequence). This area would be under tension during a frontal impact, so possibly one not bad enough to cause visible damage, but enough to set it up for fatigue later on.

FWIW my steel bike (braze/lugged) cracked similarly 5 or 6 years and thousands of miles, after I was doored and ever so slightly bent it.

Barry2 

Are you sure it's a crack and not a scratch in the paint?

Barry

alcjphil

OK, that is funny

alcjphil

Are you sure about this? I see some rust near the crack

Trakhak

Yep. Also, I don't think Trek ever produced an aluminum 520. And none of their aluminum bikes that I remember had discrete-looking steel-ish welds like those in the pictures. Pretty sure Trek's aluminum frames progressed from bonded assembly without visible joining to big obvious stack-of-dimes welds.

In any event, the bike appears to have been repainted, which most bike companies say voids the warranty.

Did the OP buy this bike new? If not, was it already painted when bought from the previous owner? If so, that might be suspicious. And there'd be no warranty, of course.

Thulsadoom

I bought the bike new. It's been repainted several times. It has over 55,000 miles on it so I'm not especially interested in a warranty claim, I mean...c'mon. I just thought it was a strange place to crack.

alcjphil

Good information to know. Still, only 55,000 miles? should last longer than that

FBinNY 

No, hence "seems".

I did notice what looked like rust by the headset, but I've also seen that on aluminum frames.

However, everything I posted would also apply to steel, except that tube defects are much rarer.

The difference is that fatigue and crack propagation are much slower in steel.

alcjphil

The OP seems to have owned this bike from new. Perhaps they can provide more info about frame construction and material

Andrew R Stewart 

Just guessing but with so little to go on- That crack has been there for a while given the rust showing on the edges/face in photo 1 and 2. That the rest of the bike shows a lot of surface rust suggests a lot of exposure to moisture and maybe salt. No surprise there's rust on the crack too. We don't know whether this bike has ever been bumped from the front (and a big enough curb/pothole is the same) but to my eyes this looks like a crack that started on the tube's top side, roughly centered along the tube. The path of the crack has that sort of jagged shape that suggests possible embrittlement and/or tube defect spot. The crack follows a path of tearing/separation into the stiffest part of the joint.

We could ask about the history of this bike and there are "incidents" that can stress the frame but not show at that time. But the crack's varying shape and path suggest it started a while ago. I would love to see more informative shots of the crack and rest of the bike before being too sure as to what might have happened, or not.

BTW one of the next possible questions might be "can it be fixed"? Sure but I would want to have a serious assessment of the frame and fork conditions overall to make sure some other failure is pending. This might require the paint to be removed in some spots, certainly the frame and fork will need to be bare of any components. The 520 is enough a "cool" bike to consider a fix for the fun of it (if it were mine) but I seriously question the value to have a pro do it. Andy

GamblerGORD53

You're crying about a rusty old repainted bike with 55,000 miles breaking? LOL. I bet there's ZERO surviving bikes with those miles, age and use.
Haven't you heard TREK is going broke?? Go buy a fricking NEW 520 bike.

Aubergine 

if we can assume the OP correctly identified the bike it's definitely steel. The 520s were completely steel up to 2020 or so, when they added an aluminum fork (sacrilege!!) to the steel frame.

FBinNY 

No problem. It's why I said "seems" though aluminum or steel the answer is basically the same.

Note, I'd added a BTW referencing my n steel frame that died the same way roughly 5 years after a seemingly minor collision.

FBinNY 

Sucker bet. Plenty of (most?) steel bikes last that and longer. We don't hear about it because few people ride anywhere close to that in a lifetime.

79pmooney

Random observations and questions. That crack did happen 1" from the highest force point on the bike, the fork crown at the headset. All of the bending moment on the fork, both routine from rider weight and road vibration to potholes to bunny hops to car doors ... happen there and in equal and opposite direction by the head tube, assisted by the down tube. That tube juncture is the most critical to keeping the bike and rider off the road.

I have never liked the idea of welded steel bikes. I am much more comfortable with the idea of lugs, especially for production bikes made in large numbers. Welds are hot. That heat extends quite far from the weld itself. How much depends on the mass of the parts to be welded and to welder skill. Same is true of brazing but the brazing temperatures are much lower. I have often wondered how long welded frames last. I didn't start seeing high quality welded frames until the late '90s. Just now, those frames are starting to get to what I call the "mature years" of good steel frames, 50k miles.

This bike has shown something I do not want to see on my bikes. First crack in a critical place. I've lived through (barely) a bike breaking that one inch away. I've also retired bikes with broken BBs, chainstays (2 or 3 times), had repaired seat stays, chainstays and BBs. My Peugeot UO-8 failing at the chainstay at 22,000 miles and dozens of crashes - a good failure. No one gets hurt. Likewise BB shells, seatstays. But that fork at the crown? My nightmare. My strong opinion is that bike should be so built that something in the back of the bike always fails before any frame part between the front hub and the handlebars and including the front 6" of the top and down tubes. (Excepting in crashes big enough to obviously bend or break the frame.)

Bikes, if ridden long enough, break. They all do. The manufacturer of the bike can do things to improve the odds that the failures happen at "safer" places. So, sounds backwards, I see it as good practice to make the BB details or chainstay or seatstay details a little less bulletproof so they don't do go forever. I am one fully guilty of riding bikes into the ground. That Peugeot. A half dozen winters on salt roads, two car doors (retired on the 2nd) ... My Miyata 610, a very well built frame - retired on its 3rd hard, fork ending crash. Now I am in my later years. I now longer make frames old muscling big gears up hill. But I still want a fork, headtube and headtube, top and down tube lug attachments steel) I trust completely (or ti welds there by a builder I trust) so I never have to go through that nightmare again.

Thulsadoom, you caught this in time. It's steel so the crack developed slowly enough to be noticed. (One reason I love steel.) All good! A happy ending for a frame that has served you well. Now, if you really liked that frame, consider taking it to a custom builder and asking him to "make me another, only tweak this, put a braze-on there and I really like those lugs!" (My Mooney was built to be the non-racing bike to replace the Fuji Pro I loved but was race only. Now 3000 miles behind your Trek, 2nd paint but maybe midway through its life (if someone takes it on after I go, it's going to outlive me by many years).

FBinNY 

Let's not go overboard here. The frame cracked and is I obviously toast. However, brazed, silver soldered, or welded, there will always be a heat affected zone of a few inches, with a gradient from the joining temp. down to room temp. Along this zone there will be a band where the temper has changed in a way that's more prone to crack formation. This is why butted tubes were used, adding some extra strength to offset heat damage. This gas always been true of all steel frames, mist of which still serve for a long time none the less.
‐-------
1st hand story below for those patient enough to read it

Many years ago I got to watch what happens in real time. A good friend had crashed his custom 531 bike, causing a very minor D/T upset. We reminded him that 531 is prone to cracking this way, and he should have it retubed, but he wasn't ready. A few years, and countless reminders go by, but it's beginning to sound like Chicken Little, and Marty's clearly tired of it.

So, one fine Sunday we're out riding and someone happens to look over and see a crack opening up under the D/T.

"Yo, Marty, your frame is cracking"
"STFU, cut the BS already, it's gotten old".
Seriously, we're not kidding, you need to stop now!"

Two or three minutes of each of us coming abreast, and the nonsense continuing, until, the frame spoke up, "Doink", and the wheelbase got longer, lowering Marty gently to earth, held together by the now curving top tube.

Richard Cranium

IMHO - Metals can be very strong and rigid (most of the time) because they have specific "networks" of molecular connections that resist change. These network connections can be deformed or degraded after a metal is reheated and joined to another piece of metal. Usually an additional attention to soldering (or welding) the joint makes it as strong or stronger than the metal that's being connected.

However, there is no cheap way to determine how much "change" there has been made to the pieces being heated for connection. In this case an over attention to the strength of the joint - may have actually weakened the tubing nearing the joint. In bike frames with external lugs frame tube the cracks often appear at the edge of the lug. Not really so much unlike what's pictured in this post.

.

79pmooney

How much money are willing to plunk down that my Mooney won't go another 3000 miles? And at 52k, 45 years and a few hard crashes, it rides like a new bike. Someone posted on BF recently of a bike of his with twice my bike's mileage.

Thulsadoom

A couple of band-aids should fix this right up!