NOTE: This post is rated PG-13 for mild strong language, coarse humor, and mature themes.
This post is about how—and why—to build a soda-bottle human-powered air compressor for inflating tubeless bicycle tires. For a few dollars you can create a non-electric equivalent of that giant, loud, coin-operated air compressor that you might use at a gas station.
I freely acknowledge that I did not invent the soda-bottle air compressor, nor am I the first to showcase it on the Internet. But I’ll give you a more thorough account than you’ll get elsewhere, which might a) prepare you for the kinds of difficulties you might encounter (since I encountered them all), and b) give you the opportunity to laugh at me. You’ll also get some safety tips.
Why build your own compressor?
My friend Peter (“Uncle Peter” to my kids) is like a superior version of me, except that he can’t be bothered to blog. He introduced me to the human powered air compressor concept, via an e-mail to John, Dan, and me, which included this photo:
Uncle Peter wrote, “I went riding with some jackass this summer and we were on a dirt road and he flatted twice thanks to pinch flats ... the humanity!” He was of course referring to me, and this ill-fated ride.
John and I were cycling teammates in 1981 and have been friends ever since. (He lives way far away and my kids couldn’t pick him out of a lineup, so he’s not yet an honorary uncle.) He replied to Uncle Peter’s e-mail: “So many questions… First, this looks like a home brewer’s still, not an air compressor. What are the details on this contraption? You can buy an actual air compressor for about $100 —why go this cheap route?”
It’s very tempting to take John to task for being a yuppie, not being resourceful, etc. but I would just sound bitter. Probably he was baiting me, and if so it worked—I’m a cheap bastard, allergic to throwing money at a problem. It’s not that $100 seems like a lot to me (though it does); any time I buy anything I feel a sense of defeat.
Meanwhile, there are non-fiscal reasons to make your own compressor. For one, electric compressors are loud and take up a lot of room in your garage, whereas you can throw the soda-bottle generator in the trunk of your car. (Perhaps John is reading this and thinking, “You can buy an actual portable gas-powered generator for about $400 to power your compressor with—why go this cheap route?”) Dan replied, “I love the idea of pulling up to the pre-race parking lot extravaganza, where everyone is pretending to not be checking each other out, but that is exactly what is happening, and then pulling out this plastic bottle thing. You would automatically get a call-up at a Cross Crusade race I think.”
Now, regarding a portable non-electric solution, some reader is going to bring up CO2 cartridges so I’ll head him off at the pass. Yes, there are little disposable CO2 cartridges that many people use to seat tubeless tires. But I hate this solution. First of all, it can take several tries to seat a tire (especially a new one) which means potentially going through a lot of cartridges. Plus, we embrace how hard cycling is … why be wusses about it and clutter up landfills with these cartridges? And, they cost money.
Naturally that won’t be good enough for some of you, so I’ve done a little homework about another downside of CO2: it leaks out of your tires faster than air. Someone told me this has to do with the size of the molecules, but I wasn’t sure I believed it. In fact, as described here, the size of molecule isn’t important, but “the leakage rate of CO2 is huge, and the reason is that it is actually soluble in butyl rubber and is thus not constrained to normal permeation loss; it can transfer straight through the bulk rubber resulting in severe tire pressure loss.” This explanation, and the empirical tests confirming the theory, are corroborated here. But I wasn’t sure if this phenomenon applied equally to tires vs. tubes (i.e., to a tubeless setup) until I read this article. It not only gives the same explanation—“CO2 is actually soluble in butyl rubber—it essentially melts right through the material without having to wait for permeation”—but the writer tested CO2 vs. air on tubeless car tires. Despite the thick rubber, the difference in leakage rates was demonstrable.
Which leaves the final alternative to this soda-bottle compressor: one of these fancy new tubeless-specific floor pumps with an extra chamber that compresses the air in advance. (That is, it does the same thing as this soda-bottle compressor but without being kludgy.) What’s wrong with this approach? Well, this pump and this one are butt-ugly. They’re also really expensive—even more so than a compressor. And this (also expensive) Lezyne pump looks really nice, but I already have five Lezyne frame pumps and two Lezyne floor pumps and don’t want another. My most recent Lezyne purchase was a high-volume pump that supposedly can seat a tubeless tire. It cannot. And, after the first time I used it on a Schrader valve, its over-designed chuck—which is supposed to work on either Presta or Schrader—doesn’t work at all, on anything. Don’t get me wrong, Lezyne pumps are really nice, when they don’t suck like this. I’m almost as bitter about this pump as my wife is. (She doesn’t know a pump chuck from a hole in the ground, but she can count, and I have more than ten bike pumps in all—she wouldn’t stand for another.)
A final note on these pumps. The marketing people must think they’re pretty clever with the naming: “Flash Charger,” “Pressure Over Drive,” “JoeBlow Booster.” You know what, guys? If you wanna get really edgy, I dare you to name your next pump “Blow Job.” I double-dog dare ya.
How does this homemade thing work?
I’ll answer both interpretations of this question: 1) what is the method for building and using this contraption, and 2) how well does it work?
Even after the basic justification for this compressor was supplied, John replied, “But I still don’t understand—is there water in the bottle? Or do you just fill the bottle with air (using a standard pump) and then connect that piece of fish tank pump tubing to the valve on your wheel? For some reason I’m thinking there would be some water in the bottle, but I’m not sure why (the incompressibility of water would help for some reason…? Boy my physics knowledge and intuition has totally atrophied…).” Before you malign my friend, consider that he has a Ph.D. in geophysics from UC Berkeley. But that didn’t stop me from ribbing him: “No, there is no water! Stop trying to turn everything into a bong!” (This is an inside joke: John, Dan, Uncle Peter, and I are among the seemingly rapidly collapsing minority who don’t smoke weed.)
Dan chimed in, “I was looking at that contraption and thinking that you were making moonshine on the weekends! Cheers to that. But you burst my bubble of mirth and raised my curiosity. How did you seal the valve to the plastic bottle? Caulking?”
The answer is, you drill two 5-millimeter holes in the bottle’s screw-top cap, far enough apart that they don’t touch but close enough together that they don’t touch the edge of the cap. You take a couple of old Presta tubes, cut off all the rubber around the valve, shove them through the holes, and then screw down some valve rings really tight with a pair of needle-nose pliers. (For an invaluable discussion of valve rings, and bicycle inner tubes in general, click here.) Thankfully, no caulking is required.
The next step is to remove the valve core from one of the valves. Do this with the little plastic wrench that came with your tubeless tire valves, or with some needle-nose pliers. Now, a quick aside: you don’t need the full tubeless kit that comes with the fancy rim tape. Just buy the tubeless valves, a bottle of Stan’s NoTube tire sealant (or “jizz” in the vernacular), and some Gorilla tape. (Is there a better product than Stan’s? I don’t know and I don’t care.)
You’ll also need a spray bottle full of a water/dish soap solution. And you’ll need some extra Gorilla tape (or duct tape), a 2-liter soda bottle, a pair of vice grips (or some other crimping device), and of course a floor pump. Finally, you’ll need a foot or two of surgical tubing. (What diameter? I asked Uncle Peter what he used and he said, “I think it was 4mm. About the size of your dick.” Nota bene: 4mm is the inside diameter. Of the tubing.)
Okay, because you’ve been so patient with all this text, here’s a pretty picture.
As I’ll get to later, you should eschew the 1-liter bottle shown above and go with a 2-liter Schweppes bottle.
Next, you shove one end of the tubing down over the valve that has the core removed.
The tubing should be a jolly tight fit over the valve. You could use electrical tape to secure it, but don’t bother. First of all, it’s extra work. Second, I have discovered that under sufficient pressure, the tubing will pop off, but this isn’t a bad thing. Think of it like a fuse: if the tubing pops off, the bottle won’t explode. And you really don’t want the bottle to explode. That would be very loud, and possibly dangerous. That’s why you wrap the bottle in duct tape or (ideally) Gorilla tape.
How likely is an explosion, assuming the tubing doesn’t pop off the valve? The good news is, these bottles can take a lot of pressure. I saved you the effort of researching this by finding this video showing how much pressure various bottles can take before exploding. Most 2-liter bottles can handle 150 PSI. The Schweppes bottle doesn’t explode at all; rather, it splits a seam and the air hisses out harmlessly at 140 PSI. That’s the bottle you want!
Fortunately, with a 2-liter bottle you’ll only need about 60 PSI to inflate a brand-new tubeless mountain bike tire, so the explosion risk is quite low. That said, you should absolutely wear safety goggles just in case.
To get a new tire ready to be seated, you should mount it to the rim with an inner tube inside, pump that bad boy up good and hard (the maximum the tire is rated for), and leave it overnight. Then, remove the tire and tube, remove the old rim strip, and tape up the rim with your expensive fancy-pants purpose-built rim tape or the Gorilla tape. If using Gorilla tape, you’ll have to cut so it’s the perfect width for your rim. Use a safety razor blade or a utility knife. If you don’t cut the tape just right, or if you use the wrong width purpose-built tape, then you are not a good person and should take up some other sport, like golf. (That is, you won’t have a perfect seal.)
Then, install your tubeless-style valve but don’t tighten the ring down very tight just yet. Mount the tire to the rim (without the tube, duh), leaving one section open. Pour in the jizz (whatever amount the bottle says—I think it’s 2 ounces?), then seat the rest of the tire. Hang the wheel from something, like your bike stand. Now spray soapy water all around the bead on both sides. This will help the tire bead seat. That’s the name of the game here: that bead has to make an airtight seal all the way around. What makes new tires such a bitch to mount is that they are shipped all folded up, and those creases create giant gaps where air leaks through like a sieve.
(Now, if this all sounds like a total pain in the ass, consider that most of the hassle here isn’t specific to using a homemade human-powered compressor. Tubeless is inherently kind of a hassle, but then so is puncturing during a ride. Obviously it’s worth the trouble or we wouldn’t be here.)
Okay, so this is where it all comes together. You shove the other end of the surgical tubing over the valve stuck in your rim. You pinch the tubing closed with your vice grips, some inches from the valve. And you attach your pump chuck to the valve on your compressor that has the valve core intact.
And—don’t skip this step!—you put on your safety goggles. Here’s the whole setup in one photo:
Then you whale on that floor pump like there’s no tomorrow. Pump the soda bottle up to about 60 PSI, maybe 70 if it’s a really fat tire. Then release the vice grips and—whoosh!—all that air flows in with a quickness, and if you’re lucky, the tire will seat, making this glorious popping sound, and you’re good to go.
Now … did this work for me? No. My first three tries were dismal failures. Look at that photo above: what mistakes can you see, right off the bat? Well, first of all, I used the one-liter bottle that Uncle Peter sent me. (He built my compressor. There. I said it. I was tempted to leave that kind of vague, so you might think I made my own, and frankly I’d planned on making one, but before I got around to it, Uncle Peter mailed me one he made. This astonished me. He hates going to the post office. When I left my helmet in his car once, it took him like 8 months to get it to me.)
For a road tire, whose pressure is higher but whose volume is way lower, a one-liter bottle is probably fine. It also worked great when I removed and re-seated a used mountain bike tire. But it’s not enough air volume to mount a new mountain bike tire. Don’t even waste your time. Just buy a two-liter bottle to begin with.
What else did I do wrong? The wheel wasn’t hanging from anything. The deformation of the tire, where it touched the ground, surely hurt my cause. Man, what a waste of time and spirit. I had my daughter making a video of all three efforts, which wasted her time too, and surely eroded her respect for me (a precious, rare resource). A neighbor friend even happened by to witness my disgrace. Damn. I called Uncle Peter and he pointed out all the mistakes I’d made. “Man, you’re the worst student I’ve ever had!” he jeered.
So, I headed to the grocery, bought a 2-liter bottle (alas, I hadn’t seen the video and didn’t know Schweppes was the ticket), drank a glass of (grossly cloying) ginger ale and dumped out the rest, taped up the bottle, hung the wheel from my Park stand, summoned my camera operator, and tried again.
This time it didn’t work at all. Something was horribly wrong. Finally it hit me: I’d forgotten the vice grips. I wasn’t compressing anything. Easily solved. I clamped those bad boys down and tried again.
This time the tire came a lot closer to seating—it actually got some shape to it—but alas, the flow of air wasn’t quite fast enough and found a way to leak out. For a terrifying moment I battled despair and was on the verge of rending my garments, gnashing my terrible teeth, and roaring my terrible roar—but my daughter was there filming. So I confined the profanities to my interior monologue and made one final tweak to my setup: I removed the valve core from the valve installed in the rim. This would, I hoped, speed the flow of air into the tire.
Did it work then? Well, check out this video!
Yeah, baby! It’s not the greatest camera angle, and you can’t hear the bead popping in, but that’s for safety’s sake. I had my daughter stand way back and use the camera zoom, because I only have one pair of safety goggles. Suffice to say, this time the compressor worked like a champ! Alas, when I pulled the tubing off, the air rushed out fast enough that the tire unseated. So I had to inflate it one more time, and this time I was ready with my thumb when I pulled the tubing off. I managed to get the valve core back in without the tire unseating, and my long ordeal was finally over.
Now, I’ll give you one final word of advice. Once you’ve got the tire seated, you shouldn’t just leave it. You should put the regular pump on there and inflate the tire to its maximum rated pressure. Then tighten down that valve ring (you left it loose before in case the base of the valve fought with a tire bead). Then you need to give the wheel a good spin, and shake it back and forth (like you are trying to bop yourself alternately on the forehead and then the belly with the tire), moving your hands from place to place. Here is a good video of that process. Then bounce the wheel on the ground a whole bunch of times. Then set it horizontally across a trash can for a few minutes before flipping it over. This sloshes the Stan’s jizz around in there so it coats the whole inside of the tire.
But even if you do all that, you still might not be done. The first time I installed tubeless, I did all that, and even bounced my wheels on the ground for several blocks while walking home from the auto repair shop. Everything seemed fine, even the next morning, but by afternoon when I wanted to ride, one tire had lost its pressure and puked jizz all over the floor of my garage. So I highly recommend you go for a short ride once your tire installation is complete, to spread the Stan’s around even more. If possible, take your camera operator with you on the ride, if he or she is your offspring, so you can justify the project to your spouse as “quality time.” If your offspring is shy about being photographed during this victory lap, snap an artsy photo like this one.
Is there an even better compressor out there? Well, consider this user comment to one of my blog posts:
Great device. I think he don’t feel tension who has a Kensun AC / DC Heavy Duty Air Compressor Tire Inflator Review. Because it is portable and anywhere we can carry this for pumping tire and best air compressor I have ever seen in market
Note: I can’t vouch for Charles’s knowledge of compressors, or for Charles being an actual human.
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