ATTN: Framebuilders...couple of Q's for ya...

Spicy McHaggis

New Member
Local time
9:04 PM
Feb 2, 2008
What size tubing do you find works best for a motorized bicycle frame?

I did steel, lugged (brazed) frame building as an apprentice back in the 90's, working for an Italian bicycle frame builder. We used strictly bicycle frame tubing (obviously).

What do you guys use, and where are you sourcing from?

I'm considering just going ahead and brazing a new frame...I think it could look good lugged...

I get mine local (Shapiro Supply) in St Louis. They will do cutting and mail order but I get mine cheaper because if you can get there in person and dig through the bins yourself, they sell their scrap pretty cheap by the pound. I paid $80 a couple days ago for the metal for the (non-motorized) trike I'm working on.

I've only done one rather rough-looking frame, in 1" tubing with .049 and .058 walls. This was really heavier than necessary I think.

Butted tubing is a bicycle thing--all industrial suppliers have is straight-wall. I stick with 4130 steel, the common wall thicknesses in sizes suitable for a bicycle frame are .035", .049", .058" and .065". From about 5/16" up to about 1.5" they will have every eighth-inch increment, in at least a couple of these wall thicknesses.

They have 6061 aluminum in a lot of sizes also, if you want that instead. They have some mild steel and titanium too, but not in as many smaller sizes. The titanium is about 10X the price of 4130 or 6061.

They have some oval and aero 4130 tubing as well, I was looking at some pieces in a scrap bin and wondering about taking it but didn't. The shapes looked about a 3:1 on the length:width ratio.
I used seat stays of 1/2 X .049 and chain stays a little larger if I was not using a tubeset of Reynolds, Tru Temper or Columbus tubing. I would use .035 or even less wall thickness in large diameters for the main frame tubes. For my project where I just added a rack to the back of a frame I used 1/2 X .049 to build the rack. Here is my post on that project with photos.