Extra Long Tubes

Hi all, I’m a new builder who just made his first bike recently and am looking for advice on where to buy some extra long tubes.

The bike is a “bike truck” style that will have a front rack that rests on two tubes that run from either side of the seat stay, around the headtube, and then stick out in front for the rack to mount on. Everything is done on the bike apart from this, I can’t seem to find any tubes that are long enough! The distance from the seat stay to the headtube is around 550mm so I’d probably want tubes around 900mm to give me enough room to actually build/mount a rack, but the exact length isn’t super important (I can always build the rack a bit narrower/wider). I’d also like them to be relatively thin (think mixte-style stays), but if I have to go up to 25.4mm or so that’s fine, 38.1mm is probably the absolute biggest OD that would work, unfortunately the random industrial places around here all seem to start way larger than that and I haven’t found anything bike-specific.

Any suggestions on where to buy longer than normal tubes would be appreciated!

EDIT: after posting this I realized that McMaster had some 4130 that might work that wasn’t showing up when I originally searched for some reason. Hopefully someone else will have other suggestions too though.

Aircraft spruce has 4130 tubes. They have 4130 in a bunch of diameters useful for bike building. I’ve bought 4’ lengths before.

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Online Metals or Wicks Aircraft also have 4130 tubes that would be suitable.

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McMaster is a good source. You probably want to .035in wall thickness.

If it is your first build of this bike truck design, I would always err on the side of stiffer and more durable. It’s better to be safe and have a ridable bike than to have a broken one!

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Actually, I’d be really curious if anyone knows what the difference between this and the much more expensive tubes sold by framebuilder companies is? Ignoring more specialty tubes that McMaster or the other places people mentioned won’t have (ie. double butting and the like), are they basically the same thing? I could see frame builder supply companies having finer tolerances or maybe better heat treating or something, but unless I was building something for a race team I wonder if a random industrial supplier with 4130 would be just as good?

Great question.

Bike tubes start off as these 4130 seamless tubes (like you could buy on Mcmaster), then they get drawn over a mandrel several times to form the butts. That is why they are more expensive: You are paying for the original 4130 tube, the drawing process, the shipping, etc… After manufacturing, the tube company takes a cut of the profit, then the distributor takes a cut of the profit.

That is how you end up with a tube 3-4x more expensive.

Butted tubes have higher stiffness-to-weight ratio than straight gauge 4130. Bikes are human-powered, so lighter weight always helps.

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makes good sense, so for something like this where it’s holding a rack and weight isn’t a concern, random 4130 tubes sound like they’ll be just fine! Thanks!

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