cracked frame
 

hi peeps, i didn t know were i was going to post this, i m cleaning my bike, its a giant expressions crmo frame which i use as a touring bike, i removed the kick stand an i noticed that where the stand attches, between the bottom bracket and the chain stays, there is a flat square metal, and its welding is cracked from one side, is this something i should worry about? i go to work with it so its almost loaded. i really upset becauase its a very confy and strong bike :(

thanks

david

No. Don't worry about it. Just have a welder reweld it back together again.

Just disassemble the bike. Find a welder (most autobody repair shops have welders), and have him reweld the bike. After that, it should be as good as new.

- Slim :)

Check how far the crack developes into the tube. You should be fine with a weld repair but bike frame tubing is thin and agricultural welders are used to to thicker stuff.

Good advice.

Bad advice.

the tubing it does not seem to be affected, since its just a metal plate to which the stand an mudguard atteches. anyway tomorow i m going to my giant dealer, see what we ll do

thanks everyone

And why is my advice "Bad advice", when we're practically saying the same darn thing? :rolleyes:

PS.

Besides, it's NOT the tubing, anyway! So your guy was on the right track. He just got slightly derailed, thinking about tubes, instead of plates...It happens...

Nonetheless, his advice is good and mine is bad!...Alright, I get it! ;)

I would stop using the kickstand and leave it. You don't need a piece of metal where that one is, it's just for the kickstand

Because you can't take a bike frame to "most autobody repair shops [that] have welders and have him reweld the bike". What you are likely to get back is a bike with a hole where a weld used to be. The steel on bicycles, including cheap frames, is incredibly thin and easy to burn through. It is a myth that a steel bike can be repaired by anyone with a welder.

A broken weld is also a stress riser which will lead to further damage down the road. The very best course is the one that dabrucru is taking, i.e. contacting the dealer.
'

Any experienced certified welder, worth his salt, can weld iron metal (steel) with relative ease, without any stress risers being indicated. As long as he is certified in both MIG and TIG welding, he should experience no problems.

"Certified"
http://www.gowelding.org/Welding_Certification.html

Looks like that is thin wall bike tubing

What about a machinist?

The steel that an experienced certified welder works with isn't bicycle tubing. A master pipe fitter, for example works with pipes that have walls around 12mm thick. Bicycle tubing has wall thicknesses of tenths of a millimeter. The thin metal doesn't weld the same and is very easy to burn through.

And a "experienced certified welded" may not work at "most autobody repair shops".

That's where I found out about how difficult bicycle tubes are to weld. I had a machinist who welds pressure vessels, fabricates delicate equipment for scientific experiments, is a bicyclist and whose welding skills go far beyond being simply 'certified'. He was astounded by how thin the steel tubes of a bicycle are and he commented that they would be incredibly easy to burn through. That just about anyone with a welder can fix a steel frame is a myth. Any idiot with a welder can burn a hole in the tubing but that's not fixing it.

Brazing might be a better option than welding, assuming it's steel.
As mentioned by others, there are many types of welding and experience. Some welding methods are more appropriate than others, and most people have their own areas of expertise.


Anyway, if just the kickstand bracket is cracked, but the frame itself is fine, then don't use the kickstand.

How about a picture ?

Can I ask how old the expression is? Here the new Expression is Aluminum with a Cro-Mo fork.

2005 I think, its a very strong and stable bike. i really love her ;)

Isn't the frame warranted for life? If you're not the original owner, or if it'd be too much bother to take advantage of the warranty, then I agree with cyccommute and homebrew01 - DO NOT take it to an auto shop. An arc welder could destroy the tubing before the operator knew what was happening. By then, an "oops, sorry!" won't cut it. I think brazing would be the best choice. No chance of destroying the tube, and it won't require a master welder.

Check for a recall, I googled my bike and found they had a recall for cracked frames....mine was cracked...they delivered a new one immediately.

Get it welded back. also tell the welder the tubing is thin so he doesn't blow a hole in it from to much heat.

THe only Giant Expressions I could find on the internet have aluminum frames, not chrome-moly. THey all claim to have the ALUXX aluminum. This makes them more difficult to weld (not that it would have been easy with steel).

Are you sure it is a cro-mo frame?

yep, its heavy as hell, and also it has the label it says 4330 chromoly....something maintube, it feels more stable with heavy loading on rear rack

i think there are only i europe, also i coudn t fine one on the web either..

Contact your nearest city's local union of welders and tell them that you're in need of the services of a good welder. Describe your problem to them and they will provide you with an excellent reference.

BTW - Steel is much easier to weld than aluminum. It's also more reliable once it has been welded. Why?....Because it's steel!

and here is 'le crack'

well to make sure put a magnate on it. If it falls off it isn't steel. But looking at the pictures it looks like it failed at the wield so it should be under warrantee.

my bikehttp://bikeforums.net/attachment.php...hmentid=244790http://bikeforums.net/attachment.php...hmentid=244789

Looks a bit like what they sold here as a Bolder with a solid front fork. I have a Trek 800 sport that is a bbit like that and is steel. However I replaced the solid front forks and went with suspension forks and a bew drive train. Still you are weilding at a wield so the old wield should be removed and redone. And find a Tig Wielder if we find that bit is indeed steel.