Hmm small crack in chain stay ...

[find_bruce]

Saw a small crack in the seat stay of my 3 month old bike. Closer inspection revealed it to be not quite so small


So its back to the retailer for me.

[Nobody]

Thanks for posting.

Please edumacate us.

What brand & model?
How much do you weigh?
Do you ride it on or off road?

Thanks in advance.

[gabrielle260]

What's the hole in the second photo?
The reason I ask is that it looks like the crack started there.
I have cracked several frames, most recently a Lynskey, so I know how frustrating/annoying it makes you feel!
Andrew

[find_bruce]

Thanks for posting.

Please edumacate us.

What brand & model?
How much do you weigh?
Do you ride it on or off road?

Thanks in advance.

Cell SS101 - alloy frame. I should also have said that it is the drive side seat stay & the hole in the first photo is of the bike upside down.
95 kg

It's my commuter - bike paths and roads, some of which are a bit rough but no off road as such.

What's the hole in the second photo?
The reason I ask is that it looks like the crack started there.
I have cracked several frames, most recently a Lynskey, so I know how frustrating/annoying it makes you feel!
Andrew

My guess is that the hole could be intended to drain any water as it is much bigger than the pinholes used to release the welding gasses & it doesn't appear to serve any other useful purpose.

You may be right about the source the crack, as that would explain why the crack did not follow the weld evident in photo 2

My theory though is that the welding evident in photo 1 was of poor quality and failed causing the hole - the crack has then propagated in both directions

[rustychisel]

from the discolouration etc it looks to have started at that big snot of a weld (photo 1) and propogated. Too hot weld point undercut the tube creating weak point = poor quality frame?*

*mostly guesswork

[rkelsen]

Not a good look for Cell. Particularly after this:

http://www.bicycles.net.au/forums/viewt ... 9&p=769861

[ozdavo]

I should also have said that it is the drive side seat stay

Looking at the dropout in the 1st pic, looks like the chain stay to me FWIW

[rustychisel]

I should also have said that it is the drive side seat stay

Looking at the dropout in the 1st pic, looks like the chain stay to me FWIW

Good spot. That's the underside of the chainstay (drive side, rear)

[il padrone]

The hole under the chainstay looks like it was never meant to be there..... ugly welding! Smacks of a "she'll be right" attitude to welding quality control.

Makes me glad my Thorn frame has had all the breather holes brazed up to completely seal the frame tubes

[find_bruce]

Looking at the dropout in the 1st pic, looks like the chain stay to me FWIW

Yes you are right, thanks

[Nobody]

Makes me glad my Thorn frame has had all the breather holes brazed up to completely seal the frame tubes

Did the factory do this?

[il padrone]

Makes me glad my Thorn frame has had all the breather holes brazed up to completely seal the frame tubes

Did the factory do this?

Yes, on the Thorn Nomad Mk2 frames, they're "handbuilt in Taiwan" and the factory does a range of special things - sealed frame breathers, SS drop-outs, SS gear and brake cable guides, 6mm rack mounts for strength - that Thorn specify.

[jasonc]

I don't think the word small should be in this thread at all.

[find_bruce]

I don't think the word small should be in this thread at all.

It was only a very narrow crack - barely perceptable from above. Wasn't all that long either.

Oh you mean the fact that it failed at the weld, spitting a piece of weld out and then progressed more than 270° around the chain stay, well there is that I suppose

[master6]

I assume that the definition of "large crack" would go something like:-

" A place where you might park a large truck"

[rustychisel]

"that's not a crack. This is a crack."

[r2160]

Have you taken the bike back yet? How did you go?

cheers
Glenn

[trailgumby]

"that's not a crack. This is a crack."

That's not a crack, that's a bike rack.

[raistian]

That's not a crack, that's a bike rack.

Soft padding guarantees zero scratch* on your bike^.

* may occasionally leave brown marks - this is harmless but not odourless
^ frequent use allows you to fit more bikes over time

[elStado]

I wouldn't worry about it. What's the worst that could happen?

[bp2]

In your first photo if you look at the dropouts you have two serated marks where the wheel was tightened.
The top mark is the correct position for the wheel. The bottom mark shows that at some stage a wheel was tightened in the incorrect lower position. This could have lead to a twisting force on the lower chain stays.

[find_bruce]

Have you taken the bike back yet? How did you go?

Yep took it back the next day thanks Glenn - have been told they will replace the frame - just waiting to find out told how long it will take

I wouldn't worry about it. What's the worst that could happen?

You're right I am being overly cautious - I should have just kept riding it while "keeping an eye on it"

In your first photo if you look at the dropouts you have two serated marks where the wheel was tightened.
The top mark is the correct position for the wheel. The bottom mark shows that at some stage a wheel was tightened in the incorrect lower position. This could have lead to a twisting force on the lower chain stays.

Thanks for taking the time to look so carefully. Whilst I have clearly tightened the axle whilst incorrectly positioned, I would be surprised if I had ridden it like that as it is unlikely that I would have perfectly matched the mis-alignment on the other side so the wheel would have fouled the close fitting mudguards.

As I have returned the bike, I can't check for matching marks on the other side