# MTB frame welding problem ? (with pics)



## mju (May 26, 2008)

This is a mtb frame from my friend.

The photo is taken from the top of the head tube.

I would like to ask that is it a regular frame or is there something wrong?


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## Walt (Jan 23, 2004)

*Certainly not how I would do it.*

It looks as if the downtube is mitered to the head tube and the toptube, but the toptube is not completely welded to the head tube.

In general, a better process is to completely join the tube that will be mitered fully to the head tube (this is usually the downtube) then miter the other tube as needed and weld it in. You end up with a lot more weld holding the joint together than if (as in this case) you just miter both tubes, stick them up against the head tube, and weld all the exposed joint.

Is it unsafe? Probably not, but it could certainly be done better, IMO. I've seen trials frames (aluminum ones) break because this type of process was used with the compound seat tube/downtube joint.

-Walt



mju said:


> This is a mtb frame from my friend.
> 
> The photo is taken from the top of the head tube.
> 
> I would like to ask that is it a regular frame or is there something wrong?


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## RoyDean (Jul 2, 2007)

Why do bike builders choose to use such a huge hole in the head tube and bottom bracket housing like that? Is it for weight savings? I hope not....


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## MichauxYeti (Nov 10, 2005)

So you can drop ball bearings into your buddy's bike when the fork or BB is out.


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## ScaryJerry (Jan 12, 2004)

Looks like the headtube is welded twisted to how it should be as well. The holes appear to be at 10 o'clock instead of 12 o'clock


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## Smokebikes (Feb 2, 2008)

Just plain sloppy...............gotta be "production". That said..........I bet hundreds of frames are built that way from that one production line.


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## MichauxYeti (Nov 10, 2005)

Actually I was thinking maybe the headtube was installed upside down. It's hard to see if there's a difference in the distance from the face to the nearest hole edge when comparing top and bottom.

Logic would seem to dictate that power transfer and stiffness are primarily affected by the tubes and connections that make up the bike's "spine", namely the head tube, down tube, bottom bracket, and chainstays. By abbreviating one of the connections it would seem to make the frame weaker overall.


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## Evil4bc (Apr 13, 2004)

I think the vent holes are jsut really sloppy .

As for the tubes not being completly welded , the builder notched the downtube and mated the toptube into it , not the best way to build a bike of this style . Better to weld the toptube in then the downtube ..if possible 

Oh and DAMm thoes are sloppy cut vent holes !


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## mju (May 26, 2008)

This frame cost me $300

Can I ride this bike to the offroad?


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## Kavik (Apr 13, 2007)

Definitely a production frame. Poor planning on the vent hole location. Sometimes they are that large so the heattreat water can exit easily. On a custom frame, one of the two intersecting tubes should have been stitched up before the other was mitered/tacked over, covering that part of the joint.

That being said...Ride it like you stole it!:thumbsup:


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## Ianbocaca (May 31, 2008)

*Headtube test report by DORCUS Cycle*

DORCUS Cycle has been tested the strength of this headtube. The resoult has higher than standard. Means strength is no problem.
In Taiwan there were so many people has discussed with this case already, then DORCUS Cycle has been issueed the test report to prove the strength is higher than standard. 
So I really don't know what's the issue we need to discuss this case again in this Formus.
Also the compare pic. (Merida) which you post in here is not appropriate because the tubing shape is totally different with DORCUS


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## MichauxYeti (Nov 10, 2005)

I'm not sure what you're trying to prove with some small and blurry pictures. What testing standard does this comply with? How does it compare to a frame built with the top tube mitered around the downtube? How does it compare with a frame where the headtube vent hole doesn't extend over the weld joint?


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## coconinocycles (Sep 23, 2006)

*the proof is in the pics.......*

that is crappy fabrication, and for a couple different reasons. it LOOKS like the TT isn't even mitered, doesn't it? steve.


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## OliverHart (May 31, 2008)

mju said:


> This frame cost me $300
> 
> Can I ride this bike to the offroad?


WOW. Such a crappy built frame costs $300?

I think you are hijacked. 

The ACCESS XCL frame sold in PerformanceBike is a much better deal if you are looking for bargain HT frames.


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## pvd (Jan 4, 2006)

Just ride the bike. If it brakes, get a new one on warrenty. If it doesn't then it didn't matter.

Bikes are for riding. Once they are painted, the time for worry and fussing is over.


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## disease (Nov 27, 2007)

Ianbocaca said:


> DORCUS Cycle has been tested the strength of this headtube. The resoult has higher than standard. Means strength is no problem.
> In Taiwan there were so many people has discussed with this case already, then DORCUS Cycle has been issueed the test report to prove the strength is higher than standard.
> So I really don't know what's the issue we need to discuss this case again in this Formus.
> Also the compare pic. (Merida) which you post in here is not appropriate because the tubing shape is totally different with DORCUS


How can anyone be expected to have confidence in a company with a name like DORCUS?


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## cyclomatt (Mar 4, 2008)

disease said:


> How can anyone be expected to have confidence in a company with a name like DORCUS?


Dorcus means gazelle in Greek.


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## Scudweiser (Jul 13, 2008)

this makes me feel like tearing apart my bikes and whatnot to check the welds


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