Steer Tube Length Modification

[The Renaissance Man]

This is one of many possible ways to alter the length of a steer tube. I'm not an expert, so use your own judgement before making any modifications yourself.

The Shockmaster fork that I'm using is from a girl's bike and therefore is too long for a boy's bike. Typically you could section the tube and weld it back, but because this one is in such poor condition, I'm going to use a donor fork. If you need to make your fork longer, you would also need a donor.

The first cut needs to be below the depth of your stem when it's installed at its lowest point. This will prevent the weld from interfering with the stem adjustments. Make this measurement from the top of your desired length, not the current length. I would make this an even measurement from the bottom so that the math is easier in the next step! A pipe cutter works well for this.

After the first cut, measure from the bottom again and then subtract that from your desired length. The result will be the measurement for the next cut from the top half of the donor.

After cleaning everything up, chamfer (bevel) the edges of both cuts. Here's a link to help explain why this is important:
http://www.weldguru.com/SMAWNomenclatureandJoints.html


You need to keep everything straight for welding these parts back together. A simple jig for this can be made from a section of angle iron. To keep from crushing the tube with vise clamps, I used a couple of hose clamps. I also marked a center line on both pieces so that the groove would be in the correct position.

For more security, a sleeve can be inserted to bridge the inside of the two parts. In this case, the I.D. was smaller on the bottom half and would've required a step machined into it so I chose not to add it. If it is welded correctly, it should be very strong even without it.

The two pieces are spot welded on each side and then removed from the jig and spot welded in two other quarter locations the rest of the way around. This keeps the metal from pulling as you add more heat. Check and make sure that nothing has moved before finishing the weld.

I should note that this is done with a TIG welder.

After the welding is complete and the metal has cooled (sorry, I forgot to take a picture here), I used a flat file to level the weld with the tube so that the bottom race will slide back into place. I prefer to do this by hand so that I can control it better and not remove any more metal than I have to. With a fillet weld, there's not a lot to remove anyway.

It's now ready for some primer after a quick visit to the bead blaster!

Thanks to my cousin Charlie for the welding. He's been welding on street rods for as long as I can remember!

 

[pick]

Great thread! Hope I can find it when I get around to needing it.

 

[B607]

That's a professional looking job for sure. Nice work. Gary

 

[mikeeebikey]

Very nice welding!

 

[XC204]

Excellent job on the fork TIG is the way to go! I have one at home but no blast cabinet yet.

 

[The Renaissance Man]

Great thread! Hope I can find it when I get around to needing it.

Thanks Pick, maybe cman will post it in the HOW TO MANUAL- Index.

That's a professional looking job for sure. Nice work. Gary

Very nice welding!

Gary and Mikee, I wish that I could take credit for the actual welding. It was all done by my cousin who has countless years of experience. He has encouraged me to use his gear, but for this job, I didn't want to risk doing it improperly.

Excellent job on the fork TIG is the way to go! I have one at home but no blast cabinet yet.

You are absolutely right Gary. I'm sure that someone using a MIG could also do this, but the TIG is far more precise and is better suited for such thin material. If you look closely at the pictures, you will notice that there were some gouges toward the bottom that were also filled with the TIG and filed smooth.

 

[bits n pieces]

I keep the two pieces straight by cutting the fork lower, tapping in a cheap deep well socket, piece of thicker bar , anything that slides in both tubes tight . I make sure to slide it at least 2 inches deep into both tubes. Drill a small plug hole into the tube on the fork and partway through the support you added. I spot weld the small hole closed. Do the same to the top after it sits flat against the fork tube. Then i proceed to weld the seam as you did. Ive stretched and shortened a lot of tubes and never had one break.
Very nice tutorial !

 

[ozzmonaut]

Just use the welding magnet hanging on the bench in the pic of him filing to keep it straight. No jig neccessary. Those magnets are $2 at the flea market and very useful

 

[The Renaissance Man]

bits n pieces is right, if you can fit a sleeve inside without interfering with your stem, it will add strength.

ozzmonaut, magnetic clamps are useful in a lot of situations, but in this case it would be too close to the weld and would cause what is called "magnetic arc blow". TIG welding is especially susceptible to this problem.

Here's more information on the subject: http://home.btconnect.com/diversetech/layer2/zeropr.htm

 

[Walker]

I've used a section of handlebar for an internal sleeve. cut about a 1-1/2" long piece, split it longwise and it slides right in.

 

[Sinner4]

Good Work, looks like new. I need to do that to a 1 1/8 to make it longer by 3 inches. I read the E Bay description wrong.

 

[sensor]

Glad to see others take the time to use a file. They sing when you get into a groove. ZZZ.ZZZ.ZZZ.ZZZ.
I'm going out on a limb and guessing you enjoy the time spent working on things. :wink:

 

[ozzmonaut]

bits n pieces is right, if you can fit a sleeve inside without interfering with your stem, it will add strength.

ozzmonaut, magnetic clamps are useful in a lot of situations, but in this case it would be too close to the weld and would cause what is called "magnetic arc blow". TIG welding is especially susceptible to this problem.

Here's more information on the subject: http://home.btconnect.com/diversetech/layer2/zeropr.htm

Thanks, I've only used them on flux core wire welding, and my friend uses them for arc at work, but neither of us has ever touched a TIG. Glad I found out now instead of whilst trying it.