Christoph Doerffel wrote:
> > One question I would like to ask is what is the normal dimensions of the
> > square tubing used by selfbuilders.
> for solo bikes 40mm x 40mm x 1,5mm
> for tandems 60mm x 40mm x 2mm or 50mm x 50mm x 2mm

For a well constructed frame 1,5mm wall thickness is sufficient even at a
tandem. The Zox tandem uses 2mm because it has very long single tube-parts
and a long main tube. But even with the 2mm wall thickness it is still not
very stiff.
Our BTB-tandem has 50x50x1,5 and it feels quite stiff. But it has very short
parts of one single tube only.

So think about a good frame design and you can save some weight, too.

Martin
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