Cracked Head

[Samcycles]

So I've had my Cube town hybrid SL 500 for just over a month and covered 155 miles and today as I was checking the bike before my ride I discovered a crack in the head tube.

Now I've seen head tube cracks before and mostly they start at the top or bottom edge but this crack runs from the weld between the top tube and the head tube on the RHS and runs down and around the head tube. The crack is around 55mm long.

Needless to say I've contacted the dealer and Cube directly but I wondered has anyone else experience of this kind of frame failure.

 

[GLJoe]

Now I've seen head tube cracks before and mostly they start at the top or bottom edge but this crack runs from the weld between the top tube and the head tube

Hard to tell from the picture, but it looks more like a scratch than a crack!

 

[Samcycles]

Hard to tell from the picture, but it looks more like a scratch than a crack!

That was my first thought too and I was going to polish it out then I looked at it under a magnifying glass.

 

[vfr400]

I think it's a scratch because there isn't really any way that it could get a stress to open up a crack in that location or direction.

 

[TobyAnscombe]

Drop the fork and have a look from the inside..

 

[Andy-Mat]

So I've had my Cube town hybrid SL 500 for just over a month and covered 155 miles and today as I was checking the bike before my ride I discovered a crack in the head tube.

Now I've seen head tube cracks before and mostly they start at the top or bottom edge but this crack runs from the weld between the top tube and the head tube on the RHS and runs down and around the head tube. The crack is around 55mm long.

Needless to say I've contacted the dealer and Cube directly but I wondered has anyone else experience of this kind of frame failure.

If truly a weld crack, it looks as though after welding, the manufacturer did not "de-stress" the metal. There are several ways to do it, but generally I believe that the welds have to be heated up and slowly cooled, but there may be more modern methods that I have not heard of.....
Dreadful and possibly very dangerous on a road bike, if that suddenly gave way and dropped you onto sharp metal and the asphalt.....
Well seen.
Regards
Andy
PS. I just looked around on the web and found little information. This is probably the best, but I don't find it good myself:-

Reduction of welding residual stresses and distortion

Welding residual stresses have a negative or positive effect on the strength of the component depending on their type, sign, direction and distribution. Triaxial tensile residual stresses in combination with cracklike defects promote brittle fracture. Uniaxial or...

link.springer.com

 

[Samcycles]

I think it's a scratch because there isn't really any way that it could get a stress to open up a crack in that location or direction.

I hope you're right. Although if it is, it's a really deep scratch and I've no idea how it got there. Taking it into the dealer tomorrow for inspection so fingers crossed.

 

[grldtnr]

I hope you're right. Although if it is, it's a really deep scratch and I've no idea how it got there. Taking it into the dealer tomorrow for inspection so fingers crossed.

There is a non -destructive way to test it , to see if it's cracked, but I am not sure what it's is, to my mind it isn't cracked ,just scratched, but it's best you take it back, for an exchange. If the company is reputable ,they should accept your concerns.

 

[TobyAnscombe]

It can't be a crack as that would be a longitudinal crack in a tube; the stresses required to essentially crack the steel there (noting that its quite some distance from the weld) would be pretty impressive. Ally just doesn't crack that way.. be interested to hear what the outcome was.

 

[Samcycles]

I'm pleased to report that as most of you said it's not a crack. That's the good news. It is a however a deep scrape right down into the metal which has had some type of filler applied, some more was removed from the scrape while being checked. Once the filler had come away the scrape became visible.
The story I've been told is that the frame may have been damaged during the factory build as it is so deep and in an unusual place and this was how it was repaired. I'm not convinced by this but at least I wasn't accused of doing it. They are going to talk to cube and will come back to me with a resolution. They did point out there are no more available so it couldn't be exchanged which I'm ok with. I will post an update when they get back to me.

 

[RobN]

Take a cash offer and stick a sticker over it.
That's what I would do.

 

[vfr400]

I'm pleased to report that as most of you said it's not a crack. That's the good news. It is a however a deep scrape right down into the metal which has had some type of filler applied, some more was removed from the scrape while being checked. Once the filler had come away the scrape became visible.
The story I've been told is that the frame may have been damaged during the factory build as it is so deep and in an unusual place and this was how it was repaired. I'm not convinced by this but at least I wasn't accused of doing it. They are going to talk to cube and will come back to me with a resolution. They did point out there are no more available so it couldn't be exchanged which I'm ok with. I will post an update when they get back to me.

That sounds very feasible to me. The filler shrank when it dried to leave the crack.

 

[Andy-Mat]

I'm pleased to report that as most of you said it's not a crack. That's the good news. It is a however a deep scrape right down into the metal which has had some type of filler applied, some more was removed from the scrape while being checked. Once the filler had come away the scrape became visible.
The story I've been told is that the frame may have been damaged during the factory build as it is so deep and in an unusual place and this was how it was repaired. I'm not convinced by this but at least I wasn't accused of doing it. They are going to talk to cube and will come back to me with a resolution. They did point out there are no more available so it couldn't be exchanged which I'm ok with. I will post an update when they get back to me.

It remains to be seen if that is the good news or not, but at least you can ride without any problems, where a crack might have made it dangerous to use!
Best wishes
Andy.

 

[Samcycles]

I've had contact from the dealer and have an offer of store credit. Which I'm happy to accept.
I have a theory that the scratch happened when the bike was being unpacked at the dealers warehouse and probably by someone using a Stanley knife, realising what they had done they must have tried to cover it up with the filler. Mistakes happen I guess.
I'm thinking of trying a car scratch repair kit to fix it.

 

[Andy-Mat]

I've had contact from the dealer and have an offer of store credit. Which I'm happy to accept.
I have a theory that the scratch happened when the bike was being unpacked at the dealers warehouse and probably by someone using a Stanley knife, realising what they had done they must have tried to cover it up with the filler. Mistakes happen I guess.
I'm thinking of trying a car scratch repair kit to fix it.

If you can purchase the identical colour and paint type, a quick and easy fix is to have a "lint free" cloth (old pair of much washed jeans will also work!), soaked in the paint.
But first clean the crack/scrape with meths (do not drink!), then rub the soaked cloth "across the crack", (not along its length), which will remove paint from the lint free cloth, filling the scrape. Let it dry in the sun and a day later, do it again.
For anyone who doesn't know where the crack is, it is invisible, even if you know where it is!
I have done this on several "keyed" cars, and one that hit a garage wall, over the last 40 odd years.
Its far more effective than "thinking about it" seems to be!
Andy

 

[Samcycles]

If you can purchase the identical colour and paint type, a quick and easy fix is to have a "lint free" cloth (old pair of much washed jeans will also work!), soaked in the paint.
But first clean the crack/scrape with meths (do not drink!), then rub the soaked cloth "across the crack", (not along its length), which will remove paint from the lint free cloth, filling the scrape. Let it dry in the sun and a day later, do it again.
For anyone who doesn't know where the crack is, it is invisible, even if you know where it is!
I have done this on several "keyed" cars, and one that hit a garage wall, over the last 40 odd years.
Its far more effective than "thinking about it" seems to be!
Andy

Thanks Andy, I'll give that method a go and I promise not to drink the meths.

 

[Andy-Mat]

Thanks Andy, I'll give that method a go and I promise not to drink the meths.

Do let us know how you get on.
Good that you posted, I forgot to mention the last part of the work (Maybe I tried the Meths!), my apologies.
The work leaves paint streaks on the otherwise pristine paint, either side of the scratch.
Do not try and clean it up too much, but when you consider it otherwise finished, 24 hours after the last application, use toothpaste on a wet cloth and clean all the rest away.
Once you are happy with that, wash it, let it dry a further 7 days, then burnish with car wax polish.
My sincere apologies, but I have not needed to do it for a long time!
regards
Andy

 

[Samcycles]

Do let us know how you get on.
Good that you posted, I forgot to mention the last part of the work (Maybe I tried the Meths!), my apologies.
The work leaves paint streaks on the otherwise pristine paint, either side of the scratch.
Do not try and clean it up too much, but when you consider it otherwise finished, 24 hours after the last application, use toothpaste on a wet cloth and clean all the rest away.
Once you are happy with that, wash it, let it dry a further 7 days, then burnish with car wax polish.
My sincere apologies, but I have not needed to do it for a long time!
regards
Andy

Thanks again, when completed I will post some pics of the finished results.

 

[Andy-Mat]

Thanks again, when completed I will post some pics of the finished results.

Looking forward to a really great looking job!