# changing head tube diameter?



## veryavgwhtguy (Jul 31, 2008)

I want to bounce an idea off the frame builders... I have this late nineties Jamis chromoly frame with a 1" head tube. I would like to fit a 1 1/8" Reba fork on the Jamis.

I was thinking of cutting the Jamis head tube vertically down the front (one cut total, vertically through the round Jamis logo in the picture). This would allow expanding the tube so a 1 1/8 tube could be slid inside and welded. I'd increase the weld area by a couple of methods such as plug welds, slightly longer 1 1/8" tube, grinding slots in the Jamis tube, etc. I'd probably do a gusset from each side of the down tube to the 1 1/8" head tube just to be on the safe side.

I've stick welded on car suspensions and steering quite a bit, but never a bike frame. Can I simply use 7018 rod, preheat, and let the sparks fly? Any suggestions?


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## Walt (Jan 23, 2004)

*Time for a new bike*

Your welding experience is not particularly relevant to bikes, unfortunately, and you will ruin the frame. Get something else or live with the Jamis as-is.

-Walt


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## Eville140 (Nov 26, 2010)

Another semi-cheap option would be a good, generic frame and swap everything over. 
Either eBay or 
http://bikeisland.com/cgi-bin/BKTK_STOR20.cgi?Action=List&SubCategory=Parts: Framesets-ATB

$100 can get a pretty decent frame


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## veryavgwhtguy (Jul 31, 2008)

Walt said:


> Your welding experience is not particularly relevant to bikes, unfortunately, and you will ruin the frame. Get something else or live with the Jamis as-is.
> 
> -Walt


Can you be more specific?


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## laffeaux (Jan 4, 2004)

Once you've re-welded the head tube with the "expansion joint" added, do you have a plan on how to make the head tube round and a consistent 1-1/8" diameter?


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## Blaster1200 (Feb 20, 2004)

This is funny and the point where most people are quietly thinking "Epic Fail!" but are too nice to say it. 

I think you're probably dead set on doing this regardless of what people say. So instead of listening to common sense (such as selling the frame while it still has value, and buying a cheap frame), go ahead and prove everybody wrong and just do it. Please post pics along with your explanation of why others shouldn't consider doing what you propose. Not saying it's not possible, because it certainly is possible...to some degree, anyway.


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## Andy FitzGibbon (Jul 7, 2007)

If you love the Jamis frame, get a White Bros. fork for it- they will put 1" steer tubes in them.
Even if you did follow through with your plan (which is a bad idea for a lot of reasons), the Reba will jack up the front of the bike and will change the handling pretty significantly.


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## veryavgwhtguy (Jul 31, 2008)

Really, what I most want to know is if 7018 is the correct rod for 4130 steel, and if not, what is? I'm not married to the fitment plan necessarily (was thinking about removing old head tube completely as another possibility).


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## Cracked Headtube (Apr 16, 2006)

veryavgwhtguy said:


> I've stick welded on car suspensions and steering quite a bit, but never a bike frame.


This quote sums up why your plan will not work. 
Stick welding has no place in modern bicycle fabrication. The gauge of the tubing will likely fail after this modification. No, your chosen rod will not work. 
if you like your Jamis frame so much to continue to ride it with a significant change, you should value it for what it currently is, and leave it be. 
if you want a better fork, look for a Marzocchi with a 1" steer. I believe they were made up until 2007. 
you asked frame builders' opinions, and they were given.


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## Smokebikes (Feb 2, 2008)

*"I want to bounce an idea off the frame builders... I have this late nineties Jamis chromoly frame with a 1" head tube. I would like to fit a 1 1/8" Reba fork on the Jamis.

I was thinking of cutting the Jamis head tube vertically down the front (one cut total, vertically through the round Jamis logo in the picture). This would allow expanding the tube so a 1 1/8 tube could be slid inside and welded. I'd increase the weld area by a couple of methods such as plug welds, slightly longer 1 1/8" tube, grinding slots in the Jamis tube, etc. I'd probably do a gusset from each side of the down tube to the 1 1/8" head tube just to be on the safe side.

I've stick welded on car suspensions and steering quite a bit, but never a bike frame. Can I simply use 7018 rod, preheat, and let the sparks fly? Any suggestions?"*

DO IT, and take lots of pictures of the process, post the success or failure................always learn.


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## pyranha (Aug 7, 2007)

It is highly likely you will blow holes in your tubing if you try to stick weld your head tube. You would have to use super thin rod and be really careful. In a past life I spent 4 years in the Navy stick welding. At the top of my game, I would not have tried what you are suggesting.
The small builder I worked with to learn to build frames is not shy about doing this kind of repair/modification. He did a beautiful job changing a lugged Ciocc frame from 1" to 1.125" by cutting out the head tube, enlarging the diameter and tig'ing in "patches" and then putting a new head tube in(he has been building for 30 years). It was a road bike, and used as a bike path bike for a friend of mine to pull his daughter around in a Burley trailer....but I digress. 
I guess my point is that there is a way to do it but you are slightly off in the direction you are heading. 
That being said, the above posts are on point in that it would be more cost effective to buy a cheap-ish frame and call it a day.


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## FoCo29er (Dec 5, 2010)

a new frame is relatively cheap compared to new teeth...


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## Actual Size (Jan 24, 2006)

I have seen Mikkelsen do this repair several times, Cuts out the head tube, Re miters the top and down tubes 1/4" back, Mills a new head tube, Welds it back in, Frame repair is not something you should try with out a lot of experience !!!!! Bernies got a few years in.....


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