Is it a crack?

g-man
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Is it a crack?

Postby g-man » Tue May 01, 2018 9:32 pm

Hi All,

I noticed what I believe to be a crack in the alloy frame of my Giant Defy, along the edge of the weld where the seat stays connect to the seat tube.

I took it to a bike store who put in a claim with Giant, but the Giant rep who inspected it denied warranty claiming it was just a crack in the paint / corrosion.

I can’t see how it’s possible to be sure that it’s not a crack in the frame. The location on the edge of a weld seems to be a very common place for a crack to form, and it seems very unlikely that the paint would start to peel or crack exactly along the edge of the weld (without a crack in the frame).

Anyway, to me it seems they are trying to avoid honouring the lifetime warranty and leaving it up to me to prove / find out if it is a crack or not. I don’t want to confirm that it is a crack if it fails catastrophically while I am riding it at speed.

Any opinions (See image), and thoughts regarding where I could go from here?

Image

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10speedsemiracer
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Re: Is it a crack?

Postby 10speedsemiracer » Tue May 01, 2018 11:38 pm

That looks like a crack to me, especially considering placement.

Easy way to determine would be to plug the tube below the level of the crack, fill with water (put some harmless food dye in if you like) and check for leaks. May need the tube to be manipulated/flexed to simulate normal usage though.
The other option, but this means losing some paint, would be to flake some of the paint off the crack edge with a sharp knife (not sanding) to allow for better examination.

Last option is to have the frame X-ray tested, but this costs, and I doubt Giant would pony up the $s after the fact.
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Derny Driver
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Re: Is it a crack?

Postby Derny Driver » Wed May 02, 2018 12:08 am

Giant are usually excellent with warranty replacements.
Take it to another rep.
Or go above their head straight to the head office.
Just insist that they replace it.

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Duck!
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Re: Is it a crack?

Postby Duck! » Wed May 02, 2018 12:23 am

Looks like a crack to me. Plus being on the edge of a weld is a classic failure point. What is unusual is that it's on the back of the seat tube; seat tube/top tube junctions are far more prone to cracking, due to the rearward pressure from the seat post.

It is unlikely to just spontaneously fall apart on you (i.e. fail "catastrophically"), but will grow. Put a fine texta mark at each end of the crack, and then observe for any growth, and take photos of any crack progression so you have a record of advancement. As 10speed suggests above, pick a little bit of paint off either side of the crack, between the texta marks that you're going to put on; that will expose the underlying metal and show any cracks. At leat being a silver paint job won't show up too badly.... Keep your shop in the loop. If you can show then that there is progression in the failure, that will give them a bit more grunt in your favour.

DISCLOSURE: I work in a shop that is a Giant dealer. To be honest I find the response from Giant (or the rep) surprising, as their current warranty guy is pretty good. Would have been different two or three years ago though; the guy they had then I believe had a few personal issues going on that were affecting his work.... On a good day he'd be awesome to work with, but on a bad day was a nightmare. If that was in my workshop I'd be pushing hard in your favour.
I had a thought, but it got run over as it crossed my mind.

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Duck!
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Re: Is it a crack?

Postby Duck! » Wed May 02, 2018 12:36 am

Derny Driver wrote:Giant are usually excellent with warranty replacements.
Take it to another rep.
Or go above their head straight to the head office.
Just insist that they replace it.

Reps don't really have much to do with it. Either employed or commissioned agents, they have a set territory to work, and one has to go a fair way from base to get into a different rep's territory.

In any case warranty claims don't (according to Giant policy) even go through the local rep, they're from the shop direct to head office. Which then circulates into my previous comments...
I had a thought, but it got run over as it crossed my mind.

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AUbicycles
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Re: Is it a crack?

Postby AUbicycles » Wed May 02, 2018 5:44 am

My first thought is that it is a crack... but look at the paint lifting / bubbling above the crack area.

It is an unusual spot and I am wondering is seat tube movement with the pivot point at the weld has indeed caused the paint fracture.

If this is a fracture, I am speculating that it is unlikely that the aluminium tube is cracked, rather the weld is weakening. The way to find out is to start scrapping back the paint around the area but please get a few more opinions first.

human909
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Re: Is it a crack?

Postby human909 » Wed May 02, 2018 6:49 am

AUbicycles wrote:If this is a fracture, I am speculating that it is unlikely that the aluminium tube is cracked, rather the weld is weakening. The way to find out is to start scrapping back the paint around the area but please get a few more opinions first.

Pretty much this.

Personally I'm not really sure it is a crack, but it is damn hard to tell. It could just be a bridge of paint cracking that formed across the line in the weld. I'd be scratching away that paint with before and after photos to be sure.

Poke around with a pin if you want to be more gentle. Also apply flex to the tube by putting alot of forward pressure on the seat watch that seam while doing so.

That said, duck has probably seen more cracks than many of us...

Duck! wrote:Looks like a crack to me. Plus being on the edge of a weld is a classic failure point. What is unusual is that it's on the back of the seat tube; seat tube/top tube junctions are far more prone to cracking, due to the rearward pressure from the seat post.

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queequeg
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Re: Is it a crack?

Postby queequeg » Wed May 02, 2018 9:08 am

AUbicycles wrote:My first thought is that it is a crack... but look at the paint lifting / bubbling above the crack area.

It is an unusual spot and I am wondering is seat tube movement with the pivot point at the weld has indeed caused the paint fracture.

If this is a fracture, I am speculating that it is unlikely that the aluminium tube is cracked, rather the weld is weakening. The way to find out is to start scrapping back the paint around the area but please get a few more opinions first.


The crack looks almost identical to the crack that I had years ago on my Trek FX alloy frame (actually, on TWO Trek FX Alloy frames). The crack developed directly along the weld line, but not actually the weld itself. Due to the location, I did not spot it until it failed, shearing the entire seat tube from the bottom bracket, but leaving the weld intact.
When they replaced that frame, I watched it closely, and a crack started to develop in exactly the same place as the first one, so I kept an eye on it, and when it progressed I took it back and it was replaced (again) under warranty.

So, I would be certainly concerned enough with that picture to say it's definitely a crack and not just some paint coming off.
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Jmuzz
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Re: Is it a crack?

Postby Jmuzz » Wed May 02, 2018 11:56 am

There is corrosion under there, can see some bubbling.
But I would want some paint scraped away before accepting that it's just paint.

Perhaps they did use some more sophisticated method.

I would put detergent on it and spray air compressor down there. If it bubbles then thats instant confirmation that it's a real crack. Though it can be an airtight cracked weld too so doesn't rule it out if no bubble.

JPB
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Re: Is it a crack?

Postby JPB » Wed May 02, 2018 2:52 pm

My vote is crack.
Another test but probably impractical is soak the area in kero or similar light fluid then dry it off and sprinkle talcum powder on it. Any fluid that was in a suspected crack will stain the talc.

hunch
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Re: Is it a crack?

Postby hunch » Wed May 02, 2018 7:18 pm

A Giant I had cracked in the same spot - as well as at the BB....I'd be inclined to think it is one!

If it was me, I'd get an eddy current test if they were being difficult. Can suggest a quick google for NDT in Silverdale if your location is Sydney environs.

human909
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Re: Is it a crack?

Postby human909 » Wed May 02, 2018 9:28 pm

Jmuzz wrote:I would put detergent on it and spray air compressor down there. If it bubbles then thats instant confirmation that it's a real crack. Though it can be an airtight cracked weld too so doesn't rule it out if no bubble.


Most cracks wouldn't be full penetration. So tests like this and similar are unlikely to yield useful results.

koshari
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Re: Is it a crack?

Postby koshari » Thu May 03, 2018 8:26 am

hunch wrote:A Giant I had cracked in the same spot - as well as at the BB....I'd be inclined to think it is one!

If it was me, I'd get an eddy current test if they were being difficult. Can suggest a quick google for NDT in Silverdale if your location is Sydney environs.

an hour of NDT services would be more expensive than buying a new frame.
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hunch
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Re: Is it a crack?

Postby hunch » Thu May 03, 2018 10:04 am

koshari wrote:
hunch wrote:A Giant I had cracked in the same spot - as well as at the BB....I'd be inclined to think it is one!

If it was me, I'd get an eddy current test if they were being difficult. Can suggest a quick google for NDT in Silverdale if your location is Sydney environs.

an hour of NDT services would be more expensive than buying a new frame.


As someone who gets crack testing done from time to time on a fairly regular basis, unless the frame is really cheap and nasty.....I doubt that will be the case. If however, someone's spending an hour on this, I'd expect you'd be getting screwed on both pricing and billing hours!

Here's the blurb for this particular technique -

"Eddy current crack testing of metal parts, including painted titanium, aluminium and magnesium parts."

Anyhow, probably try Giant direct as suggested, as a next step, rather deal with reps.

g-man
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Re: Is it a crack?

Postby g-man » Fri May 04, 2018 7:05 pm

Thanks all for the opinions / suggestions.

I think I’ll try again with Giant in the first instance, as I’ve also heard that they’re quite good with frame warranties (was one of the reasons I bought a Giant!).

I’m convinced that is is a crack. Being a mechanical engineer for me it seems intuitive as it is a textbook location for a crack to form (along the the “toe” of a weld, due to stress concentrations, and residual stresses from production etc.). Any corrosion would be a result of the paint being damaged as a result of the crack, it’s unlikely that the paint would crack on its own without some relative movement of the underlying frame. I was quite surprised that the rep did not think it was a crack.

I’ll keep you posted how I go. I was also considering also pressurising the seat tube slightly and checking for leaks with soapy water, but as suggested above that would only work if the crack fully penetrates the tube.

skyblot
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Re: Is it a crack?

Postby skyblot » Fri May 04, 2018 10:17 pm

Scrape some of the paint off, and look at it with a 10x magnifying glass. Most non destructive testing is designed to help you quickly find a (possible) crack. The area is then closely inspected to confirm the indication. X-ray being the exception - it will show sub surface flaws. NDT methods are prone to showing surface flaws like scratches, hence the close visual inspection to confirm if there is a crack....

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