Cold Setting Front Triangles

Hi all,

I recently made a front triangle for a hardtail, and a few things went wrong. I just rolled with it though. While that was on hold, I built another one for a gravel frame which came out much better, I understand better, how much miters matter, and how to braze in order for it not to pull to one side too much.

The first one however, is quite out of alignment. The headtube and seattube have enough of a difference in angle to see when looking down the seattube to the headtube. I don’t have a surface table but think there’s about 1° to 1,5° of difference in angle. What would the preferred way to fix this be?

  • Try coldsetting it like this
  • Cut off Top Tube, try coldsetting HT and if that works, braze in a new TT.
  • Just bin it and rebuild with new tubing.

Thanks for the help!

With modern off-road bikes you’ll likely kink the tubes trying to cold set them. But since you can always build a replacement, there’s little harm giving it a try.


Echoing what @manzanitacycles said:

On one of my earlier builds (number 4 or 5) I really flubbed a down tube. It was out by, I dunno, 5mm maybe. I tried to cold set it once, nothing moved. I tried to cold set it again with a little more force, maybe I got 0.5mm movement. The third time I ended up on my ass, my shop mate was literally pointing and laughing, and the down tube was kinked at the butt.

All three options offer you a bunch of new experience and practice (consider that your tuition).

I would hang parts on the bike just to get a sense of what an out-of-alignment bike rides like. Have fun on it for a little bit and start the next bike. When the bike is done, swap parts. THEN start working on fixing your mistakes. By going about things this way, you’ll have a bit more torch control and understanding of construction. Things that could help your understanding of the repair.

And then, for the repair itself.

  • I’d first figure out what exactly is off and by how much (ST? HT? DT? A combo?).
  • Then I’d decide on a method of repair that offers the most learning potential. In other words, just cold setting doesn’t offer you too much. But cold setting to the point of failure, then replacing the tube gives you a whole lot more experience to apply to your next builds.

And, if you need encouragement, a lot of these fuck-ups feel meaningless in the moment. It’s not until later that you realize “Oh, that taught me how to prevent this issue and how to fix this new fuck-up.”


What are the DT and TT diameters?

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Have you seen the post about flame straightening? I’m not sure how to link a different thread/post but it’s in a thread about frame alignment that comes up of you search flame straightening. It seems like a very powerful method of alignment with less risk of buckling tubes. Even if it can’t get you all the way there it would probably help and be a cool learning experience.

I buckled the down tube on my first frame trying to align the heat tube and down tube. It was a good lesson to always have a hard stop for whatever you’re trying to cold set. As soon as the tubing starts to yield it suddenly takes much less force and it can be really easy to pull or push too far.


Hey thanks for that! in addition to all the things before it’s nice to hear these things sometimes. I think for now I’ll start the Front triangle from scratch again, I’m making it for a friend so want it to ride nice! After that ill mess around with the one out of alignment and probably try some

Of this technique first, I’ve heard a bit about it and I know that Drust cycles (don’t know if they are on here) only uses flame straightening and no Cold setting whatsoever. So worth a try I think.

As for the tubes, they are a 46mm headtube, 38 mm downtube with a bend (29er family columbus) and a 28,6 toptube. I think the downtube is too ridgid to bend well and will probably fail spectacularly when coldsetting :-).

Thanks for all the advice everyone!

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38mm and 28.6 respectively

Yup I think that is way too beefy to cold set!

@normaali has posted some great videos and info on flame straightening:

I found their demo very eye-opening: