I found a cracked frame that looked FINE until I wiped it down

Had a bike come in for a tune-up last week, everything looked normal until I hit the seat tube with a rag and saw a hairline crack running about 3 inches down. The owner had been riding it for 6 months like that. Anyone else find hidden frame damage this way?

3 comments

3 Comments

hall.joel1mo agoMost Upvoted

What kind of rag did you use that picked up the crack so clearly? I've had a few frames where light and angle mattered more than the rag, so a shop rag might not catch everything. That's a solid reminder to check seat tubes and chainstays with decent lighting before calling a frame clean.

vera_johnson91mo ago

I mean, that's a good point about lighting but did you actually try pressing on the area with the rag? Like, a lot of hairline cracks I've found only show up when you push a little, the fibers catch on the edge you can't even see. Maybe it's just me but wouldn't a fresh microfiber with some tension reveal more than just a shop rag under normal light?

the_jana1mo ago

Vera, you're totally right about the microfiber thing, but I gotta push back a little on the "fresh" part. A brand new microfiber can actually be too grabby and lint up on you, especially if it's one of those cheap ones from the auto parts store. I've found that a well-worn microfiber that's been washed a few times works way better because the fibers are softer and less likely to leave fuzz behind. Also, pressing with a rag works great for paint cracks, but what about bare carbon? You don't want to push too hard on a damaged layup or you could make the crack worse. Just something to think about before you start poking at suspect areas.