[Closed] Calling all STW engineers - possible crack?

if it's not a weld then is there any other option than paint?

EDIT: genuine question.

given it's not welded on that edge and the crack is along where the shock mount and frame meet, it's almost impossible to be a crack in the aluminium & far more likely to be the paint.

Yeah it's not welded there. It's spot welded at each side so that is most likely just the paint cracking.

If the paint is cracking, that means something underneath the paint must be moving. Which it [i]probably[/i] isn't meant to do.

Have you got any warranty on it? If you have, get thee to the shop...

I'd say crack in the paint. Slight deformation of the tube under loading would occur in this area.

Cheers guys - I'm hoping it is just the paint work. Off to see jedi for a jumps and drops course on Wednesday so hoping it'll hold up!

Its a secondhand frame so no warranty 🙁

Edit: I was probably talking balls.

It is a crack in the paint, I would not worry at a ll

Ir bandits is right, regardless of whether it's paint or metal (paint at the moment), the question is why has the paint cracked. The second question is then what is the paint cracking then going to affect? All things considered I would continue to ride it and keep and eye on it, when I could afford it I'd replace it. I haven't checked my frames since I last cleaned them.... Ages ago so have no idea if there are any cracks there or not!

What bike is it? Looks like my old Commencal which cracked there. I'm sure it was a crack, but I ran it like that for over a year and no change. If you have any chance of a warranty, use it. Otherwise get over it - It'll get bigger long before it catastrophically fails breaking your teeth / beautiful face / ruining a ride.

Paint cracking at stress points isn't anything new or alarming.

Metal will bulge, bend and distort all over the bike in microscopic amounts during regular riding all the time - the elasticity ensures it pops back into it's shape.

However paint has next to no elasticity and is incredibly brittle. Hence why at high stress areas you start to see these small cracks.

Combined with the fact that's an area paint is covering two bits of unwelded metal, I'm not surprised a paint crack has developed there - not matter how good a fit that gusset/bracket is it's never going to be perfect so the paint has to "bridge" over there.

TL;DR: I wouldn't be worried personally.

A sure fire way to check is to look on the other side of the welds - as in the sides facing away from each other. Any cracks there?

Chris (Not an engineer)

As said, it could be paint crack where metal isnt joined from slight flex = no problem

As also said, it could be paint crack from slight flex that aluminium is intolerant of and could start to affect the welds either side forming fatigue stress fractures over time. Actual time depends on loading and frequency of that loading. Fatboy bouncing around heavily will affect if more than skinnykid only riding gentle xc!

If you have warranty then let them know and ask them why your paint finish isnt fit for purpose, even just as a marker for a later frame failure claim.

Edit

Metal will bulge, bend and distort all over the bike in microscopic amounts during regular riding all the time - the elasticity ensures it pops back into it's shape.

That's the problem with ally frames, the high strength alloys are for strength not elasticity - so are highly prone to fatigue hardening

Looks like a sticker 😉

looks like paint to me - you could remove the paint in that area and check -

Is that a front shock mount?
I would be surprised to see a crack there however as people have said the material can and will move then return so long as it remains elastic. Over time repeated trips in the elastic region caused fatigue failure.
I would do the paint removal thing if I had no warranty and had a touch up pen!

Is a engineer by the way.

Looks like a crack in the paint on the unwelded joint - but why would a frame builder leave a metal to metal joint unwelded? Looking at the weld that are on it doesn't give much confidence; from the photo, the one on the right looks like one of the worst bits of welding I've seen anywhere, not just on a bike.

"one of the worst bits of welding I've seen anywhere, not just on a bike"
Made in halifax perchance?

that's just a thick bit of paint that sits where two parts butt up. Wouldn't worry about it myself.