I know it's easier and cheaper to work with steel, but is it THAT MUCH easier and cheaper?
Why almost every custom framebuilder builds steel bikes, but not many work with aluminum?
Given how expensive the labour is in frame building, and how difficult welding aluminum is by hand, I wonder if those who want something lighter than steel are skipping aluminium and going for carbon.– Chris HJun 2, 2017 at 19:33
3Steel is Real bro– CardMechanicJun 2, 2017 at 19:48
1The technology is vastly different. Plus, custom frame builders (and the people who patronize them) know that the advantages of aluminum (and carbon) are vastly oversold.– Daniel R HicksJun 2, 2017 at 21:22
My guesses are: There's more of a history of expertise of working with steel to draw upon. There's more romantic demand for steel (it is indeed 'real'). To learn to build aluminium frames by hand, and establish yourself to the point where it would be financially viable is most likely impossible. As @Chris-h points out, if you had the cash for a custom aluminium frame, just go buy yourself a made-to-measure Sarto for carbon, or Passoni for titanium if you really must have metal.– ilikeprogrammingJun 2, 2017 at 21:23
2An interesting question would be why custom frame builders don't use carbon more.– RoboKarenJun 3, 2017 at 20:03
When you consider the overall outcome - the final bike, not just the frame, hand building in aluminum rarely makes sense. Modern aluminum factory frames are hydro formed into all sorts of engineered shapes that save weight and provide stiffness and compliance where needed. There is no way to hand build an aluminum frame even close to the characteristics of a mass produced frame. Perhaps when we can 3D print aluminum things will change.
If the custom frame customer is a "money is no object" kind of buyer, you custom build a carbon frame.
This leaves the customer having a budget to work to for the final bike. The weight savings of aluminum over a quality steel frame is about 500gram (much less with a custom hand build). However, the weight savings in putting the money saved working with steel into components makes a lighter bike with better components.
Frame builders will usually switch to titanium if steel is too heavy and the budget allows for more money to be spent. Its not as light as aluminum, but easier to work with.
If you look at the needs of customers that want custom frames, and are prepared to pay for them, you find they understand more about bikes than most of us, and therefore know how small a part weight in the frame really makes to the cycling experience, and will sacrifice a few grams for improvements elsewhere.
+1, good insight about how at this point any kind of normal small framebuilder couldn't come close to having the design freedom of a mainstream bike from a big company with a bunch of hydroformed tubes. Jun 3, 2017 at 4:54
Mattnz's answer is canonical and addresses aluminum, steel, and titanium frames. Until we can easily 3d print metal frames, custom frames are going to be tube based. Hydroforming metal for one-off bikes isn't worth it and you can't easily braze aluminum (you have to TIG weld it).
But this leaves out another important material (as Chris H notes): carbon fiber.
If you want your own custom bike that has a radical (non-tubular) shape, you should do your own carbon fiber layups. This is something that you can do DIY as well as ask a custom CF builder to do.
And it can be literally any shape you want, within engineering limitations.
Metal 3D printing is already done commercially. It's just very expensive, and much more suitable for complex shapes than tubes. I'm not sure about how work hardening for 3D printed parts works.– ojsJun 3, 2017 at 11:02
Most current metal 3D printing is laser sintered which isn't very strong or CNCed which can't easily produce hollow shapes like a frame. Jun 3, 2017 at 19:41
1I've lifted a 3d printed titanium MTB, but that was a one-off demo of the engineering. It uses internal bracing like bird bones.– Chris HJun 4, 2017 at 8:00
If you would be confident enough to take the laser sintered bike downhill, I'd give you credit. The sintered metal I've seen is very weak in tension. Looks great, wouldn't want to ride on it. Jun 5, 2017 at 18:15
@RoboKaren just seen this after a while. The one I've handled is in this video - sadly I didn't get to ride it (and I'm no downhill rider). Interestingly the next iteration was 3d-printed Ti lugs and suspension parts combined with carbon tubing - so maybe there is a route to custom carbon geometry.– Chris HDec 19, 2018 at 15:24