Curious about this seat tube, is this compatible for use on a lugged frame?
Yes, absolutely. In fact, Metal Guru even sells a lug set intended for use with this tube and a tapered top tube. Gravel Geometry Lug Set, Sloping or Horizontal Top Tube Option – Metal-Guru.com
hi Big Foot,
Yes this tube can be used with lugs, another lug set that would work can be found here.
Also, for lug less construction the top of the tube can be sleeved with a piece of chrome-moly tubing to prevent distortion.
2 Likes
That’s for the heads-up, I just ordered a couple to try out.
I used to use a Prestige ST that tapered 1-1/8” to 1-1/4” like this, but then they ovalized the bottom, so the tube stayed at 1-1/8” viewed from the side. Made it about 1-3/8” wide at the BB. We had our own design IC BB shell made for that tube, but I didn’t like that shell so I mostly used them lugless.
I even made a couple frames with that as a DT, big oval at the HT of course, for strength/durability off-road (cross or ultralite MTB). You have to be OK with 0.6 mm wall at the BB end, but I was fine with that. Your joining technique has to be excellent though.
I threw together a grocery-getter for myself with that as DT, rode it for a year then moved it along (for reasons not having anything to do with the DT — just needed the $). I weighed ~190 then and I’m naturally fast-twitch dominant (sprinter), and I like taking off from a red light fast enough to beat the cars. Like a Kilo start! Really puts that joint to the test. Anyway what I’m saying is it was stiff enough for me, and probably for you too, unless you worship at the altar of stiffness. It works because strain on a DT is mostly torsion down there, not too much bending. At least one of the ones I just ordered will probably be used as a DT.
Just a wacky idea. Oh yeah can make a cool TT also.
Thanks for the tips and advice!
Maybe this is a better question for general but what qualities should I be looking for in a tube when considering if it’s safe to use with lugs vs lugless?
(FWIW I’m intending to build a bike using lugs and fillets, haven’t practiced much tig yet)
hi Bulgie,
This being a single butted tube, the thin section (0.6mm) would be on the 1-1/8” diameter end.
I do sell a tapered double butted 1-1/4” to 1-1/8” down tube that can be found here:
Mr Big Foot,
For lug less construction there will be too much distortion with an upper wall of 0.6mm.
You would need to reinforce that area with a sleeve or just use a bulge butted seat tube instead.
3 Likes
Oh I’m well aware, and that’s how I like it.
The other tube you mentioned would be too light for me (a clydesdale) for any kind of off-road. Maybe for a petite rider?
1 Like