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Discussion Starter · #1 ·
I managed to find a nice used TIG welder that freed up some unexpected framebuilding budget so I'm on the hunt for a tube bender!

I'd love to get some input from more experienced folks on what tube sizes/radii/dies they've found the most useful over the years. I'm mostly interested in the aggressive-gravel/hardtail-mtb side of building with some occasional mini-velo/90s-era-mtb weirdness thrown in. I'm currently eying the Cobra Toob Bender since it'll work better in my small shop setup but am open to other options as well.

So far my thinking is:
  • 22mm (7/8") dia @ 115mm (4.5") radius for handlebars & chain stays
  • 22mm (7/8") dia @ 230mm (9") radius for chain stays
  • 16mm (5/8") dia @ 170mm (6.75") radius for seat stays
  • 34.9mm (1-3/8") dia @ 230mm (9") radius for seat tubes & down tubes
  • (maybe) 28.6mm (1-1/8") dia @ 230mm (9") radius for all main tubes

Let me know what has been most useful to you!
 

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I managed to find a nice used TIG welder that freed up some unexpected framebuilding budget so I'm on the hunt for a tube bender!

I'd love to get some input from more experienced folks on what tube sizes/radii/dies they've found the most useful over the years. I'm mostly interested in the aggressive-gravel/hardtail-mtb side of building with some occasional mini-velo/90s-era-mtb weirdness thrown in. I'm currently eying the Cobra Toob Bender since it'll work better in my small shop setup but am open to other options as well.

So far my thinking is:
  • 22mm (7/8") dia @ 115mm (4.5") radius for handlebars & chain stays
  • 22mm (7/8") dia @ 230mm (9") radius for chain stays
  • 16mm (5/8") dia @ 170mm (6.75") radius for seat stays
  • 34.9mm (1-3/8") dia @ 230mm (9") radius for seat tubes & down tubes
  • (maybe) 28.6mm (1-1/8") dia @ 230mm (9") radius for all main tubes

Let me know what has been most useful to you!
The Cobra is a great bender for bike tubes, but somewhat limited if you are trying to do more than bikes. I have a Cobra and a huge assortment of dies. My advice is buy the bender and the dies that you absolutely know you're going to use. Joe has always had the extra dies I've wanted in stock and is super fast to ship.

Which dies you need is really up to you. If mountain bikes are your thing then a 1.375/35mm makes sense. I have all 3 radii and mostly use the 230 because it deforms the tube the least. That being said there are occasions that I need a tight bend very close to the bb and use the 115. Just keep in mind that there will be some ovalizing of the tube at the bend so some hand filing will be needed.

For seat stays you can use the .625/16mm for both 14 and 16mm stays. It's a little tricky to hold everything since the clamp is essentially useless on the 14, but you can get it done. Again, bend radii is going to be dependent on you and the look you want/tire clearance you're looking for.

For chainstays I always use .750/19mm and a yoke so that die made sense for me but if you're planning on using off the shelf chainstays that one probably doesn't have much use.

The Cobra is tricky to make bars on and honestly not very good for it. I'd skip the 7/8. On that note, most benders wont allow you to place the bends close enough together to make a nice set of bars. If making bars is a must find a Diacro #3.

If you have more questions feel free to ask or shoot me a pm.

Sent from my iPhone using Tapatalk
 

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Discussion Starter · #3 ·
Thank you for the great response! I do see the limitations of the Cobra bender, I'm unfortunately pretty limited on permanent setup space right now which makes it the best option. There's a Di-Acro #3 on Craigslist nearby that's been torturing me but I just couldn't fit it in the little space I'm renting :(

Do you find 19mm chainstays stiff enough for your liking? I've mostly seen 22.2/23.8 stays but am not well informed on this.

Good to know about the bars! That felt more like a bonus, I won't be heartbroken if it doesn't pan out.
 

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I personally use 19mm 3/4" .035 for my mtb chainstay builds. I think 7/8' might be a little overkill, or at the very least, much harder to squeeze between the tire and chainring :)
I have all 3 bend radius for my cobra in 5/8 and 3/4 for seatstays and chainstays... sometimes its 3/4' for both, and sometimes 5/8' .035 for the seatstays... I would probably not buy the middle radius (6.75") in either size if I could go back in time. I basically never use them. Ive found i need the 4.25 radius for wrapping around the tire of a mtb with 415-430 CS length on a 29er... Same radius on the seatstays, and then I use the 9" radius in the middle of the stay for heel clearance. Hope this helps inform ya :) I love the bender, as others have said its very bicycle specific but if thats all you need then its great. Ive also been using it to make riser handlebars in 4130 and that has been fun too.
 
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