Spot the weird failure that sent this Marin to the scrap pile?

[Ren Rawbor]

As per title really, the lad experienced a rite of passage a couple of days ago & had his first frame failure. Very strange location for a crack too. Shame as he really enjoyed the light whippiness of the Palisades Trail frameset, and it's 1 1/8 so I can't even rob the fork for my Palisades

Anyone had a steel frame crack in this manner, slap in the middle of a tube with no bosses/other stress risers contributing? Will split it open fully and have a look but the frame doesn't give the impression of having lived outdoors or by the coast so not expecting rot, it was a clean frameset albeit having some miles judging by the worn out original rims recently swapped.

 

[Spankyfart]

Had a steel BMX break the top tube and bottom tube about 5-10 CM from the headtube.
With enough force (crazy large jumps in a skatepark) everything will break I guess.

We stuck in two pieces of pipe and welded it back, was like new.

 

[averagebiker]

I wonder if that break is where some butting starts/ends?

 

[7Speed]

Wow - that’s an odd one - I just dismissed that as an old sticker mark until I looked at the second picture. Too deep for a change in tube thickness From butting? Odd it’s mid tube straight as a die and missed the boss which you would have though would be a magnet to a stress fracture, and downtube only…Interested to see what you find when you pop it open.

 

[Ren Rawbor]

Had a steel BMX break the top tube and bottom tube about 5-10 CM from the headtube.
With enough force (crazy large jumps in a skatepark) everything will break I guess.

We stuck in two pieces of pipe and welded it back, was like new.

I've managed to break the downtube of my old (501 frame) road bike years ago, at the shifter bosses. Mainly due to the fact I used to hang round the local bike shop doing 180 endos & rocking horses lol. It went from solid to "wet noodle" to 100% broken in the space of one endo & then 50 feet of trying to limp it home!

Yeh @7Speed very strange IMO, this hasn't seen huge forces/stunts or jumps in the lad's ownership & looked outwardly very nice not all chipped and dinged up just some cable rub/chain rash & one ding in the seat tube. Only just realised how crap the second pic is, the crack is 90% around the entire downtube and has shifted maybe 0.5mm, with just the very bottom approx. 12mm of circumference left intact (again, the bottom being the last bit holding on points away from rust IMO)

 

[greencat]

I've seen similar in seat tubes. A friend had a right beater women's frame made out of pig iron which he said was riding a bit odd. I looked it over and spotted a very similar neat crack all of way around the seat tube. He was a heavy lad and I wondered if that had something to do with it.

 

[Ren Rawbor]

Haha that's interesting to note, I wonder if a previous owner was on the portly side then.

Anyway, I had occasion to get the grinder out today to remove a stripped crank from one of the lad's Chucker jump bikes so I took the opportunity to hack the poor old Marin apart too. Something cathartic about taking a cutting wheel to a retro '90s frame, but I digress. Here's what I uncovered...

So, not rust IMO it has some surface corrosion but not bad at all & certainly not been dunked in the sea or suchlike. Notice 2 factors possibly contributing though. Firstly (ironically the last photo) the frame sprung a little when I cut through it, head tube tending toward the steeper side so I wonder if it'd been crashed at some point and set up stress in the tube? Also, it has obviously been cracked a little while before it got to this point as evidenced by the top third of the break being polished smooth & slightly rolled over, so it's looking like an old "injury" that's been aggravated by the bike being put back into daily use.


Not sure if the crack beginning at the very top face of the tube means anything, personally I'm calling either freak manufacturing defect that's lasted 30 years or it's been damaged previously and only just failed. Incidentally, Ryan is 73kg after a Sunday dinner so he's blameless in this murder case lol