In-tube storage for metal bikes?

I’ve seen an increasing number of carbon frames use in-tube storage in the down tube. I’ve been wondering if that’s possible for metal bikes or if its only feasible for custom-laid-up carbon fiber. Has anyone else been thinking about this?

Perhaps someone with more FEA experience can model it before I YOLO cut a chunk out of a down tube.


I was considering doing a 2 piece downtube like this bike that pilm bikes made and making a screw cap to go on the end of the lower tube for in frame storage

Not sure if I like the aesthetic or not though haha. Maybe form over function will win the day.


This idea pops into my head all the time because I really like the concept in production.

I keep coming up with a 3D printed box that the tube would lug onto or would act like a yoke between the BB and DT.

Every time I go down this rabbit hole I realize I’m compromising so many important aspects (like nicely butted downtubes) to have a “nice to have” feature.


I am working on my next FS frame that I will have dt storage. It will be accessed from the bottom down at the BB. I will 3d print a plastic plug to close it up, will also make a bag to slide up into the tube to hold a spare tube and pump.


I guess it depends on how big your DT is. While convenient of the carbon crowd that they have this big void they can make use of I actually prefer keeping that crap out of my steel frame. Huge collector of moisture and crap plus as you pointed out another point of possible failure and possibly unwanted flex etc. This is obviously a personal opinion and will be interested to see what solutions people come up with. I prefer the less is more approach with my bikes and am comfortable with jersey or bib liner pockets for carrying stuff.

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When we developed the Ember and Felix we started with off-the-shelf tubing and adjusted the shape to accept the battery and accommodate wiring + other junk.

You could do something similar. Just imagine putting some sheet metal on a brake and then riveting a piano hinge and you’ve got a down tube bento box instead of a battery mount.

Since its an ebike weight isn’t a concern. Wall thickness went up significantly (I can’t remember how much but move 2x). And we had to use 6061.

PS. I apologize for the rack. That was out of my control.


Sorry, total thread derailment, but is it particularly humid where you’re at in Australia/in Australia in general? Here at 5000’ (1500m) in dry Utah I wouldn’t think twice about this. But I can also get by with being (very) lazy oiling the ways of my machine tools to stave off rust, so I’m curious.

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That actually looks pretty sweet. Not sure what you’d fit up there but. Maybe a pump and some spares.

Good thing you used the correct ‘there’ :rofl:

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Not so much humidity but Ive never seen a frame that can completely keep moisture out, especially if ridden in the wet.

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It’s a 42mm down so enough room to stuff a pump and spare tube in there along with a couple granola bars. Just the essentials.

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Slightly off topic, but I do recall seeing a 1908s touring tandem built by Tony Oliver here in the UK which ran a threaded cap and tap in the downtube for storing liquid stove fuel…

And this from Pechtregon a few years ago ran the DT as a compressed gas tank for the stove, I think:

All the best,
Dan Chambers