Field note · Materials · Cycling

Someone 3D printed an airless bike tire that actually works — and then found out the sport had already solved the problem

A mountain biker printed a rideable airless tire in flexible TPU. The engineering is genuinely clever. The conclusion is more useful than the tire: here is what your printer should actually be making for your bike.

Dreaming3D Inc. · Carmel Valley, San Diego · Print · Repair · Teach · ~9 min read · Serving all of San Diego County

Airless tires have been a concept-car promise for a long time. Manufacturers including Michelin have shown polymer-mesh wheels for years — structures meant to press on the road the way an inflated tire does, but without air to lose. As Hackaday reported on August 5, a mountain biker decided to stop waiting and print a set.

He did not put them on a truck. He put them on a mountain bike, which is arguably the harder test — repeated impacts, side loads through corners, and a rider who actually rides hard. After several iterations he landed on a design in TPU, the flexible filament, with S-shaped compliant spokes bridging the gap between the tread and the wheel. The tire printed in sections and assembled on the rim, with a separately printed rim interface holding the whole thing together. Per that report, it held up to serious off-road testing, and it was bright neon green, which did the project no harm on the trail.

That is a real result. It is also, by the account's own admission, an answer looking for its question — and that turn is the part worth reading closely if you own a printer.

Why the S-shape is the whole trick

An inflated tire is doing something subtle. Air pressure lets the casing flatten exactly where it touches the ground and stay round everywhere else, spreading load across a contact patch that continuously re-forms as the wheel rotates. That flattening is the suspension, the grip, and the ride quality all at once. Take the air out and a solid ring of plastic gives you none of it — it transmits every rock straight into your wrists.

So an airless design has to rebuild that behavior out of geometry. The S-curve is how: each spoke is deliberately shaped to buckle sideways under compression instead of resisting head-on. Spokes at the bottom of the wheel collapse, the tread flattens into a patch, and spokes elsewhere stay extended and hold the ring round. The diagram at the top of this post shows exactly that — the wheel is circular everywhere except where it meets the ground.

That last clause is where hobby printing meets its limit. Getting the deflection right for one static load is a modeling problem. Getting a polymer web to buckle and recover several million times, hot, in grit, without a fatigue crack propagating from a layer line — that is a materials-engineering problem with a test lab attached.

The punchline: sealant already won

We will not print you a tire, and you should want a shop that says so

Let us be direct, because this is the kind of project that generates phone calls. Dreaming3D will not print a tire for you to ride on. Not in TPU, not in anything.

A bicycle tire is a safety-critical, load-bearing, fatigue-loaded part. When it fails, it usually fails at the worst possible moment — mid-corner, downhill, at speed — and the failure mode is a crash. FDM parts are anisotropic: they are meaningfully weaker across layer lines than along them, and a repeating load that is harmless in one direction can walk a crack through a layer boundary in another. Nothing about our shop's process qualifies us to certify a part like that.

The experiment in the article is a good experiment precisely because it was done by someone testing it himself, iterating, and reporting honestly on where it landed. That is different from a shop selling you one.

What 3D printing is genuinely excellent at, on a bike

Here is the part the article implies but does not say: printing is fantastic for everything around the bike that is not carrying you. Brackets, mounts, storage, organization, fit parts, and the small plastic bits manufacturers stopped making a decade ago. That is a large and genuinely useful category, and it is most of our Sports collection.

And the category the article really points at: parts that no longer exist. Derailleur hangers for a frame nobody supports, a shifter cover, a broken clip on a rack, a battery door on a discontinued light. We scan the surviving part or the mounting geometry, rebuild it in CAD, and print it — that is the reverse engineering workflow in detail, and you can get a useful first look at your own part with nothing but your phone.

If you want to print flexible parts anyway

TPU is the material behind the airless tire experiment, and it is worth knowing regardless — it is what you want for grips, bumpers, gaskets, strap keepers, and anything that should bend instead of snap. It is also the filament most likely to defeat a printer that is not set up for it.

Full material comparisons live in our definitive filament guide and the shorter Filament Bible; AMS-specific behaviour including the TPU bypass is covered in how to fix your Bambu Lab AMS. If the goal is a part that survives real use, the orientation and wall-count decisions in how to make 3D prints stronger matter more than the brand of filament.

The San Diego footnote

Two local realities decide whether a printed bike accessory lasts a year or a season.

The sun. Summer UV index here runs 10 to 11, and anything mounted on a bike lives outdoors by definition. Standard PLA chalks, embrittles, and eventually cracks under sustained coastal UV. For a mount, cage, or bracket that stays on the bike, ask for ASA or PETG. There is a second version of this problem: a bike on a rack behind a car, or a helmet holder in a hot garage, sees temperatures where PLA softens around 50–55 °C and quietly deforms under its own load.

The marine layer. Coastal humidity is the reason filament that printed beautifully in March prints badly in August. This affects TPU, PETG, and nylon most. Dry storage is not optional near the coast.

We build both of these into what we spec. If a part is going to live in the sun, we will tell you to spend a little more on material rather than reprint it next summer — the same argument we make in our San Diego getting-started guide.

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