Broken Bike Frame

My mountain bike's frame cracked recently whilst I was riding it to work. It happened out of the blue so to speak - I hadn't jumped off a gutter or done anything else to give the bike a jolt.

My guess is that there was a latent defect in the frame, possibly caused by the weld nearby the crack. I would be interested to hear anyone's thoughts.

Here is a little more info on the bike to help with your opinions:

  • I bought the bike new from an eBay store for a bit less than $300 AUD. The price was fairly low so I wasn't expecting great quality.
  • The crack occurred when the bike was 18 months old.
  • The crack occurred just below a weld. (See the photos below.)
  • I ride the bike quite regularly to and from work which is about a 5km trip - it's always on the road and footpaths - never off road.
  • I would say I'm a fairly conservative rider - I don't think the bike has had any harsh treatment.

Here are a couple of photos:
Bike Frame Crack - Distant View
Bike Frame Crack - Closeup View