DIY Airless MTB Tires Actually Work

You can't buy airless mountain bike tires. The ones we do see look like science fiction, and none have ever made it to market. Yet, I was able to make these at home on my 3D printer, and here's the kicker. They don't feel that bad. Oh, this might be too compliant, wow. They work, they absorb bumps just like a real tire, and they are totally puncture-proof. They're not brake-proof, though, not yet. These are, after all, my first prototype, and we can solve many of these problems. So why hasn't a big company with real engineers and better materials brought an airless mountain bike tire to market? Why haven't viable designs from as far back as 2012 become available for purchase? Do Maxxis and Schwalbe have a dungeon full of these people? Am I next? Well, I'd have as much to lose as they do, since I am part owner of Click, a valve company. I even put them on my airless tires to stop them from rotating. But if a viable airless mountain bike tire did hit the market, I wouldn't lose sleep over it. There's more to it than just cost and performance. Road-going airless tires are totally viable. Consider this. They are more expensive and lower performing than standard tires, yet that doesn't stop people from buying them. Something like a rental bike is designed for long maintenance intervals. Downtime is lost money, so more expensive airless tires are worth it, even for a performance penalty. Might the same thing be true for mountain bike tires? Well, that's why I decided to build my own to settle this once and for all. I started with some inspiration. The science fiction-like prototypes were a high bar, with one design derived from a Mars rover. I'm not a NASA engineer. But others have made airless tires at home, while most are not mountain bike tires, some get pretty close. Often, the design consists of a 3D printed core with circles or hexagons cut into it. These designs are easy to print, and they look like they would hold up. But they're not mountain bike tires. One maker used no 3D printing at all. Instead, the suspension consisted of cutoffs of PVC bolted together with a rubber tread wrapped around it. Smart, but still not what I had in mind. Then there's Outside Brendan, a friend of mine. He made a real knobby airless tire that fits a standard mountain bike wheel. It's the only one I've seen that's truly for mountain bikes. He actually mailed it to me. You can actually see it survived his testing. And this is a rear wheel. Rear wheels take a lot more abuse than front wheels. His tread is printed on TPU, which is tough and pliable, kind of like rubber. Then this orange part is foam, which you can see he sandwiched between the tread and the core. Now, that core is a harder material. But here on the damaged part, you can see he used a lower infill to save weight, material, and to add some compliance. That's a word we'll be using a lot today to describe things that bend, mush, and compress. Overall, Brendan's first prototype is impressive. It works. It can't go flat. And it even looks like a normal mountain bike tire from far away. But it's still not what I had in mind. I wanted the science fiction tires they tease us with, the ones we never get to try. I wanted one of my own. This video is sponsored by Bamboo Lab. They make the easiest to use 3D printers on the planet. And they're an essential part of my workflow. So I began doing what a tinkerer with a 3D printer does, printing stuff on PLA. It's surprisingly durable. And it's great for printing something quick so you can hold it in your hand, iterate on it, and make improvements. And as you can see, my PLA tire segment is only a segment of a tire. Few printers are large enough for the whole thing. And it would waste a lot of filament to print a huge hoop on each iteration. So I was happy to print these segments. And if you look at Brendan's tire, it, too, is made of segments. That would also solve mounting. Have a look at this airless road tire I took off a rental bike. It's just a big, heavy piece of mostly solid rubber that you install by brute force. You literally stretch this over the rim and jam this bead under the lip. That could be one reason they don't make tires like this for mountain bikes. So to mount my tire, I made foot segments that lock together in a continuous ring. Each segment has screw holes and dovetails. This would give me an easy way to mount my tire segments to the wheel. And after some testing, I had a rough idea of how to build the tire. So I moved on to printing segments on real TPU. That's when I realized something was very wrong. On that first iteration, I used Xs for suspension because they were easy to 3D model, but they also create triangles, the least compliant shape known to humankind. Even on TPU, it was brutally stiff. But I noticed something else. At the junctions between the links, there was a glaring oversight. The thick vertical pillars joining the segments were actually worse than the Xs. I had created something that would comply in some areas and be totally rigid in others, not good for a mountain bike tire. I'd not only need to abandon these Xs, but also try to make the segments join differently. So I iterated again. I don't know about you, but I think best when I have a visual. And so each iteration I could hold and examine revealed more things I hadn't considered when I was limping through the initial designs. So I took everything I learned up to that point and went back to the drawing board. And I ended up with something a lot closer to what's on my bike right now. Is this the one? Holy crap. I even made a complete wheel out of all the test pieces, which all had the same dimensions and rim interfaces. These iterations are half the weight of the first ones and they work a lot better. Everybody who makes stuff understands that moment, the moment when the thing that you were thinking about starts to take shape before your eyes. In this case, it was a mutant tire ring full of all my iterations, but that got me amped up. I needed to yet again, iterate on the tire segment and reprint a revised rim interface. But this time I felt confident it was ready to actually ride on. So I got to printing the full tire. If you would have told me when I was a kid that I could do this in my garage during my lifetime, it would have sounded like science fiction. Most anyone with a 3D printer could produce these segments one at a time, but it would take forever. My bamboo lab H2D was working for me while I was sleeping, printing four tire segments at a time on its huge build plate. But remember, I also needed eight foot sections to fit around the rim. This part is gonna get a little bit nerdy. 3D printing is done by extruding layers of filament on top of one another, but certain shapes need some help. For example, the end of this foot section contains a sort of icicle without a layer beneath it. So the only way to print it is with a temporary scaffold called a support. These are generated automatically and they look like trees with trunks and branches. And in this case, I'm actually printing green leaves on my tree. And it's not just for fun. See those leaves are PLA, the cornstarch stuff I mentioned earlier. It doesn't stick to the filament I'm printing the feet on. So when all is said and done, the part just detaches from it super clean. The D in H2D stands for dual nozzle. So it's locked and loaded with two different filaments it can quickly switch between for supports or just to print different colors. It allows my workshop to be a prototyping powerhouse. But there I was, assembling a real 3D printed airless tire made totally at home. Talk about silly. My bright green tires were finally on real 29 inch mountain bike wheels that I could install on my bike. They looked absolutely preposterous. I could have printed these on black TPU, but I leaned into the absurdity. From the very start, I wanted each segment to be all one piece for the practical purpose of quick and easy iterations. I could learn a lot more by doing real tests than spending months working on dozens of parts, trying to guess where they would fail. That meant using a stiffer TPU variant. You might've experienced TPU on a flexible phone case or something like that. This is more similar to a skateboard wheel. So it's not tacky and cushy, but on future iterations, I could opt to use a different TPU for the knobs. And you can also see that these sections are fastened together with basic screws, no metal nuts or anything. They're easy to take back apart and effective enough for a prototype, a working prototype. So you can't see that I'm pedaling uphill here, but what I'm amazed by is how good the traction is. I'm honestly astonished. I haven't had the wheel slip yet. Let's go up this little rock. On that first ride, I started off taking it real easy, but my tires were working. And the crazy part is they didn't feel nearly as bad as I thought. They actually felt kind of good. If it wasn't for the noise every time it crunches into a tire, they like don't ride half bad. Having the kind of suspension that a mountain bike does and then riding on the dirt, which can also be soft, it absorbs some shock and vibration, but I know what a mountain bike tire feels like at really high pressure. And this felt much better than that. The traction was hit or miss. Definitely worse on rocks than it was on dirt, but overall it was better than I thought. But then I started pushing these tires a little harder. No, we're good, thank you. Okay. So the damage is isolated to one section and for sure it just keeps cascading. Like this one breaks, then the next one starts to break and it's just gonna bleed over into the other tires if I don't replace this section. And I brought a spare. Morning, how are you? Good. Okay. Just fixing a section of my airless tire. One thing I'm being super cognizant about is collecting pieces if it breaks. This is the one piece that broke off so far and we replaced it. Do not wanna leave this on the trail. It's just plastic and it's just, that's not good. My S-spoke design had some issues, but they were exacerbated by the top screws pulling out. Something I kind of worried about before I even went for the ride, but I prepared for that possibility. There's one thing that keeps failing over and over again is these top joints. It's taking damage big time. Maybe the screws weren't long enough. When I was putting this together, I was like, I should put nuts behind those, but I wanted to keep it simple. These are all notes that I have to make for version two. This first ride was giving me more useful information than I ever got in the workshop. I was making a mental list of all the things I would change in the next iteration, but as my rear wheel kept taking damage in different spots, I noticed the same was not happening up front. Not one thing happened to the front. The front's perfect. Sure, riding something faster and more technical would likely break the front as well, but it did confirm what most mountain bikers already know. The rear wheel of a mountain bike takes a lot more abuse. So that front wheel did survive test number one and the rear didn't. But I had loads of information and a very clear demonstration of why airless mountain bike tires are not sold. And unless you're a mountain biker, that reason might not be obvious. You see, my tires were 3D printed at home on one material and they were designed by a guy with no professional engineering experience. So let's assume a capable R&D lab with experienced engineers and vast resources could fix all the problems with my design. And let's assume the end result was a $300 airless mountain bike tire that performs almost as well as a pneumatic tire. So more expensive and slightly lower performance, but completely immune to punctures. This is the same commercially viable formula for road going airless tires sold today. And for mountain bikes, it has mostly been done already. The energy return wheel was functioning in 2012. And while it was not totally done, it was getting there. So on the surface, this seems viable, yet an airless mountain bike tire still has never been sold ever. And that's because punctures on mountain bike tires are not a big enough problem to warrant a trade-off. Most of us are riding tubeless tires with sealant. A puncture isn't always the end of your ride. Your tire may self heal. And if you are experiencing punctures, there are tires with heavier casings. There are rim protection inserts. The heaviest tire you can get with an insert filled with sealant is still slightly lighter than my airless tire. But it is true that even the burliest mountain bike tire with added protection can still go flat. But now we're not talking about punctures. Punctures are the least of what the hardest riders are worried about. They are smashing their rims on square edge rocks and tearing their tires to shreds. Sometimes they're blowing the rim to pieces. There's no reason to expect that an airless tire would fare better in the actual circumstances that cause mountain bike tires to go flat. So it's not that a viable airless mountain bike tire is impossible to make. It's that the problem it solves, punctures, isn't that big of a problem for mountain bikes, which would totally explain the timing on the Energy Return Wheel. In 2012, when these video clips of the Energy Return Wheel were taken, tubeless mountain bike tires with sealant were increasing in popularity. And have gained more traction every year since. Today, mountain bikes sold at Walmart are tubeless ready. So it's not that big mountain bike tires locking these engineers in dungeons to protect their IP. It's that a different technology solved the problem in a lighter, cheaper, and higher performing package. But I don't really care if it's practical. I'm already working on version two. You can see in this little section here, I've smoothed out certain failure points and even included bottom out tokens. Best of all, both the tokens and the tire knobs are printed on a slightly softer TPU for traction and compliance. Thanks to those dual nozzles on my H2D. But yeah, airless mountain bike tires will never truly make sense. So why did I bother making these tires if that was the inevitable conclusion? Well, for starters, it's fun. These turned so many heads when we were out there testing, people were interested. And if I can get people interested in bikes, I'm always going to take that opportunity. And maybe making a semi-viable airless mountain bike tire could teach us some things. Maybe a gravel or bike packing tire could be viable. Or maybe it's just learning for the sake of learning. Thank you Bamboo Lab for sponsoring this video. It's pretty great that I've already been using their H2D for the last year and love it, but you can print most everything in this video on any one of their other printers, just maybe in smaller sections. So check out the links below to support my sponsor and thanks for riding with me today and I'll see you next time.