Although I am still running road tubeless tires on one wheelset, I have been curious about developments at the opposite end of the spectrum. You can now buy inner tubes that are made of thermoplastic urethane (TPU). These tubes are significantly lighter than both butyl and latex tubes. Butyl tubes are what you’re used to running but you can also buy latex tubes, which are usually lighter than butyl tubes. Butyl tubes run the gamut from “ultralight” to heavy duty with purported weights as low as 65 grams. But a typical butyl tube you might use for fast recreational riding runs about 110 grams. Latex tubes are usually about 75-95 grams.
Considering that a TPU tube like those sold by Tubolito is about 35 grams, switching out tubes is tempting. Until you see the price tag: one Tubolito tube costs about $32 compared to a run-of-the-mill butyl tube for about $5. That’s a hefty premium! So the question is: what are you getting for that extra coin?
Tubolito wasn’t the first seller of TPU tubes but they seem to be the most prevalent. They’ve recently been joined by Schwalbe and Pirelli: the Schwalbe Aerothan tube is $40 and the Pirelli P Zero Smartube is $36. You can see that they are all extraordinarily expensive. Perhaps if TPU tubes become more popular the cost will go down. But for now the price is quite high.
If you’re racing or just obsessive about your bike weight, then the gram count is about the only thing that will matter in your decision. You’re going to be using TPU tubes because they’re the lightest, even lighter than a tubeless tire with sealant. Why is that? Tubeless tires are coated on the inside with a layer of butyl rubber, which adds weight. Then you add sealant, anywhere from one to two ounces of sealant per wheel. One TPU tube weighs less than the sealant you need and you still have to contend with the extra weight of the buyl coating.
Although I like light bikes and wheels, this is no longer my top priority. Whether it’s due to changing taste, getting older, or a developing a princess-and-the-pea mentality, I’ve been paying a lot more attention to ride quality. I like really smooth wheels and bikes these days. A bike that bucks and jolts or that rides harshly is just a drag both figuratively and literally. Riding in places that have degenerate asphalt, which is all too common in the Bay Area, really calls for mitigation from your wheels and your bike. At the same time I don’t want to be riding a heavy, inert bike—I mean, I could just ride a full suspension MTB, right?
After a long experimentation period with tubeless tires, I think I know what that technology can offer me. Tubeless tires do reduce the on-road hassle of flats as long as you take proper care by monitoring your sealant level. I’ve been using Schwalbe Pro One tires with Orange Seal Endurance on a HED Belgium wheelset. This setup is light but not the lightest. Yet it spins up quickly and generally I don’t mind the slight extra weight. They also roll rather sublimely—smooth, damping bumps and pavement roughness. But it could be better.
It may surprise you that these aren’t my preferred wheels. My favorite wheels have latex tubes. These are also HED Belgium rims but with regular Michelin Pro 4 tires in nominal 25mm width. Although I’ve used a variety of high-end tires, overall I’ve ended up preferring these tires. The interesting thing about Michelin tires is that they are undermeasured: they always seem to measure wider than the label says. Putting them on a wide rim like the HED Belgium and they balloon out to 30 mm! Oh, and they also weigh just 205 grams. So they are light and the extra girth makes them floatalicious on HED rims. As far as I can tell the casing construction, which affects ride quality, is nothing special and they’re not expensive, running about $42. So I’m not sure what ‘secret sauce’ Michelin is using to make such supple tires. In my experience latex tubes make a noticeable difference in the smoothness of a wheel. The above wheelset is the first set of clinchers that feel close to a set of high quality sewup tires, specifically the Clement Criterium Setas. The Clements are the best tires I’ve ever ridden, period. They had silk casings as supple as can be and latex tubes. And they weighed only 250 grams! (Oh, and the rim was a tubular Nisi, just 360 grams so two out of three: light, smooth, but not convenient.)
Back to the Tubolito tubes: I wasn’t sure what ride quality to expect with these tubes. When you handle them TPU tubes don’t feel as elastic as a latex tube despite being so light and thin. The inflexible feel of the TPU doesn’t bode well for ride quality since suppleness comes from the ability of the material to flex easily. I put them on a different wheelset, a pair of Astral Solstice wheels. These wheels are traditional aluminum rims but very light, about 1,400 grams, and a low spoke count, 24 front and 28 rear. The rims have a 19.5 mm internal width. I was trying out some Rene Herse Cayuse Pass tires; these tires are whisper-light, only 183 grams in 26 mm nominal width. When inflated they grow to just 27 mm on the Astrals. So this was a little like comparing apples to oranges since this wheelset is lighter but narrower than the HED wheels just to confuse things.
I ran into a series of problems with this combination of parts but they revealed a problem with the Tubolitos that I was unaware of. The tires were extremely tight and getting them on the rims required I use a tire lever—never a good thing. Naturally I punctured the tube. But that gave me an opportunity to test the special Tubolito patches. TPU is not rubber so regular vulcanizing patches like Rema Tip Tops will not work. Instead Tubolito sells special proprietary adhesive patches for repair. Conceptually they are similar to Park Tool glueless patches. You are supposed to apply pressure for five minutes to the Tubolito patch before inflating it. Long story short: the patches don’t hold well, at least for a long period. The first patch failed after a few days. I clamped the second patch in a C-clamp to apply pressure for three days. It failed after about two weeks. I now have a third patch in place that I also used a C-clamp to apply pressure. Subsequently I got a real flat and patched that. After about a week the tube went flat and I have not been able to uncover the leak. My suspicion is that the adhesive is just not strong enough and with sufficient air pressure a tunnel is created to the edge of the patch for the air to escape; after the pressure drops, the adhesive reattaches but only for low pressure (like when you’re looking for the leak!)
As for the ride quality it was merely okay. The wheels felt similar to what butyl tubes feel like if that. They lacked the distinctive “whine” that a supple tire makes when it deforms while pedaling. If you’re ridden the best tubular tires you know what I’m talking about. To be honest I can’t give a definitive answer because this wheelset is different than the HEDs: it’s lighter but narrower. So perhaps the ride quality is tempered by the narrowness (and perhaps by the slightly higher pressure I was using, 55 versus 50 psi on the wider HEDs). Or, it might have been the spoke count or the rim weight. (The HED rim is slightly heavier but has fewer spokes.)
At this point I’m skeptical of TPU tubes. They’re expensive and patching is not reliable despite best practices. Tossing out a Tubolito because it flatted is just not common sense. Even latex tubes can be repaired. The only thing they have going for them is lightness. Originally I bought three tubes, one as a spare. But I’ve put the third tube in and when it flats, I’ll try to repair it. But if that patch fails, then I’m tossing them all in the trash. It’s ridiculous to spend that amount of money for something that might not last one ride. Even sewup tires can be mended after a flat, making that $120 investment a meaningful one.
For the kind of riding quality I’m looking for, latex inner tubes provide the best solution. They’re light—lighter than butyl, they’re repairable, and they’re not silly expensive, about $15 instead of $32+. But best of all the ride quality is better than both butyl and TPU, and for me that is the most important criterion. You could say that I didn’t give the Tubolitos a fair chance—I might not disagree—but even on a slightly narrower rim I would have expected them to ride more smoothly. Don’t get me wrong: these tubes don’t feel awful, they just feel ordinary. That doesn’t justify the extra cost, I think, unless you are looking for the lightest setup possible.
Last comment: Tubolito tubes are not only very light but very small. The thickness of the TPU is so much less than butyl or latex that you can roll one up into half the size of the lightest butyl inner tube. That makes them near perfect as a spare tube in your saddle bag or pocket. They’re so light and packable that you can carry two or three and not feel burdened at all.