TPU Inner Tubes Part II: characteristics and market overview

Update Sep 2022 to include Vittoria’s ultra-lightweight offer for road.

Update Feb 2022 to include the new well-priced TPU entry from Barbieri.

TPU inner tubes have been on the market for several years now, yet they have to make significant inroads into the market. The second part of YellowCrank’s report on TPU tubes dives into their characteristics, how they compare to alternative materials such as latex and butyl, and provides a market overview. If you have not read the first part about the history of inner tubes, you can find it here: History of Inner Tubes. If you are not into details, scroll down to the bottom to see a summary of performance and the current market overview.

TPU inner tube characteristics

Inner tubes performance can be assessed in 7 areas:

• Weight
• Rolling Resistance
• Air Retention
• Puncture resistance
• Repairability
• Cost
• Environmental Impact

TPU inner tubes compete with two other materials: Butyl and Latex, Butyl being the most common, and TPU’s characteristics must be viewed concerning those materials.

Weight

TPU tubes are very light. Roadbike (700cc) versions range from race-oriented 23g / 25g (Tubo S-Tube / Revoloop race ultra) to around 40g for regular road tubes. This is less than half the weight as compared to Butyl, which ranges in weight from race versions at 50 / 65g (Continental Supersonic / Schwalbe SV20) to regular tubes at 93g /105g (Michelin Airstop / Schwalbe SV15), and still compares very favorable to Latex at 50g (Vredestein Race Latex ) to 80g (Vittoria Latex).
If looking at regular ( not race versions), weight savings can be summarised at 60g per tube compared to Butyl and 40g compared to Latex. Total possible weight savings per bike are thus around 100g. In addition, the weight saved is rotating weight, which helps with acceleration.

Rolling Resistance

Rolling resistance on smooth surfaces is mainly caused by energy loss due to the deformation of the tire/tube. The higher the pressure, the minor deformation, the more flexible material, the less energy lost in deformation. This is why lighter tubes compare favorably to heavier tubes in the same material and why there are differences between materials.
Bicylerollingresistance.com recently did a test comparing the rolling resistance of tubes in all three materials. It was found that the relatively heavy latex tube (Vittoria Latex, 80g) performed the best, closely followed by lightweight TPU tubes. A standard weight TPU tube loses around 0.7W compared to a Latex tube but saves up to 2.5W compared to standard Butyl tubes.
The tests metrics were: Speed of 8 m/s – 28.8 km/h – 18 mph tested on three tires (GP5000, Vittoria Corsa G+, Michelin Power TT), 80 psi (they also tested lower and higher psi). See more details on Bicyclerollingresistance.com

Air Retention:

Butyl is a material known for excellent air retention. How does TPU compare? In short, similar to Butyl and far better to Latex. Cyclingtips tested, and here are the results:

Puncture Resistance

Puncture resistance is an important property of an inner tube, as ultimately, a flat tube can mean the end to a race or a taxi ride home. It also impacts the ecological footprint and the long-term cost. Besides puncture resistance, other factors affect the durability; I will not address them here but rather in a later section under “other considerations.”
There are many discussions around puncture resistance and conflicting data and anecdotal evidence. Part of that has to do with a) the limited applicability of a lab test to real-world riding conditions, b) the different kinds of punctures (e.g., snake bite, sharp objects of different size), and c) the nature of anecdotal evidence (negative experiences are overly reported).
So how do TPU inner tubes perform? In theory, and if the TPU tube manufacturers are believed, they perform in line or better than Butyl tubes. Just look at the data from Schwalbe’s website:

Their Aerothan TPU tube is the one in silver, and the higher bars indicate higher performance. The orange bar is a “plastic” tube from a competitor ( possibly Tubolito??), black is the Schwalbe Xtra Light Butyl tube, green is a latex tube, and blue is the Tubeless Pro One tire (the same as used in combination with the inner tubes), but now without any tube.
Here is a snake bite test from Tubolito’s website:

Unfortunately, there are no independent puncture tests or statistics of puncture frequency in real-life conditions. There is anecdotal evidence of more frequent punctures from some cyclists, whereas others have put 1000s of miles into their TPU tubes without any issue. Until there is more conclusive evidence, I am hesitant to attribute any better puncture resistance to TPU tubes than Butyl ones. How about Latex tubes? They are supposedly more resistant to punctures from a sharp object but more susceptible to snake bites (when the tube gets pinched between tire and rim, for example, when not installed properly or when running too low pressure). The data from Schwalbe seem to corroborate this, but again I could not find any independent test. However, one sure thing is that thickness of the tube material matters, so the heavier tubes are more puncture resistant than lighter versions in the same material. Ultra-lightweight Butyl tubes that can compete in weight with the other two materials and come close to regular TPU tubes in terms of rolling resistance are quite puncture prone.

Repairability

Butyl tubes are easy to repair, and if correctly done (not with self-adhesive patches, but with vulcanizing ones), the patches last a lifetime. The same patches can be used on latex tubes if needed. Latex tubes are otherwise patched with a cut piece from an old latex tube and regular rubber cement (the type you get with a butyl tube repair kit). One thing that needs to be mentioned is that Latex tubes might rip open into a bigger hole when punctured and thus get beyond repairability. With Butyl and Latex tubes being easily repaired, how is the experience when it comes to TPU tubes? Unfortunately, TPU tubes need their own repair patches, and the experience with them is mixed. Tubolito’s own patches have apparently improved. Their Tubolito Flix-Kit gets good reviews and is reasonably cheap at USD 4.90 for ten patches. Due to these patches working on any TPU tube equally well, and there is little good data on other patch solutions (almost nothing on Revoloop’s repair kit, and Schwalbe’s own patches are not TPU -specific), I recommend using the Tubolito patches. The drying time of the glue is 30min, and it’s essential to clean the tube with isopropyl alcohol before patching, so it is not a roadside repair solution in most cases but rather a repair-at-home one. Butyl scores higher here because even you might still opt to replace your tube and repair the punctured one at home, at least you have the option to repair roadside without losing much time.

Cost

TPU tubes are expensive. On average, they cost around USD 35, with Schwalbe Aerothans being the least costly at USD 29.99. That is around ten times the cost of a good butyl tube and about 3-4 times more expensive than a latex tube. The long-term cost would be similar to butyl and latex if TPU tubes outlast them 10x, respectively 3-4x.
There is no reason to assume they do, though. So if cost is a concern, butyl is still your best bet. However, suppose you like the attributes of TPU tubes, such as lower weight and better rolling resistance. In that case, the cost is reasonable: You pay around USD 0.5 per gram of weight saved (in line with other weight savings options, e.g., lighter carbon parts), and USD 12 per watt (of rolling resistance) saved, cheaper than for example oversized pulley wheels or graphene lube.

Environmental Impact

The bike industry is lightyears behind other sectors when it comes to assessing the environmental impacts of their products and transparency of data (a reason might be that cycling is inherently environmentally friendly, and thus most lifecycle assessments (LCA) focus on the benefits of cycling over traveling a similar distance by car).
It is thus not surprising that little information is publicly (and non-publicly?) known on the environmental impact of inner tubes, from production to disposal. There are nevertheless some differences between the tube materials that are known and can be used to attempt to compare the materials. The environmental accountability of product engineering and purchasing decisions is essential no matter the product: The more significant number of us and the greater rate at which we consume, the greater is the amount of resources used and waste and pollution generated.
To assess environmental impact in its entirety, we need to look at manufacturing, use, and end-of-life of a product. For inner tubes, it’s ok to focus on manufacturing and the end-of-life stage. During use, there should not be any environmental impact (it would be different with tires, for example, that wear down and contribute to micro-plastic pollution).

1) Production:
Butyl rubber production is not “clean” by any stretch. Besides the obvious environmental impacts from being crude oil-based, there are the following concerns: Fugitive air emissions, solid wastes, wastewater, and hazardous waste. Particulate matter hazardous air pollutants (PMHAPs) result mainly from the production processes of mixing, milling, and grinding, volatile organic hazardous air pollutants (VOHAPs) are emitted when the mixing and milling of rubber compounds generate heat, and solvents liquids are added for tube making.
The butyl inner tube consists of butyl rubber and a long list of other additives that add up to over 30% of the total input. This makes a complete assessment very difficult, and it is not helpful that there is no transparency from the brands about their product composition.
Neither is there any publicly available information about the place of production, the raw material source, and how factories are monitored (pollution and work safety can vary wildly based on the production conditions). Transparency is possible, as the apparel industry has shown, with brands disclosing their supplier list, in some cases including the origin of their raw materials. Big tube manufacturers like Continental, Hutchinson, and Michelin could undoubtedly do the same.
No information on sustainability is available from brands for their latex tubes. Michelin and Schwalbe have general statements about their participation in sustainable natural rubber sourcing programs and their initiatives. However, you won’t know how much of the natural rubber (=latex) used in your latex tube is indeed from a sustainable source. This is again different from the garment industry, where individual products’ organic or recycled content is clearly labeled. Why is the sustainable sourcing of natural rubber important? The answer is simple but surprisingly not well known: The plantation of rubber trees in Southeast Asia and East Asia has led to massive deforestation of natural forests and rainforests with all the consequences to local biodiversity. A list of natural rubber production impacts includes Landgrapping, child labor, forced labor, loss of habitat, erosion, and deforestation. In addition to natural rubber, the formulation of latex inner tubes includes around eight other components, such as sulfur dispersion, Zinc-oxide dispersion, formaldehyde, colorants, and more.
TPU is claimed to be an environmentally friendly alternative. This claim is not only made about end-of-life (see further below) but also about the production of the material. See this overview from Tubolito:

While it is difficult to verify and focuses on energy, water, and CO2 emission only, it aligns with other sources. It makes sense considering that TPU tubes are far lighter than butyl and latex and thus have less material use. Another potential difference is also the source of the TPU, which is still in large quantities produced in Europe, especially for domestic uses. Strict environmental regulations and enforcement thereof have a positive impact on the pollution generated during manufacturing. What is not clear is how much of the TPU (if any) used is bio-TPU from a plant-based source such as corn. The source impacts the sustainability of production and the end-of-life phase, as typically plant-based TPU is biodegradable, whereas oil-based is not.
2) End-of-Life
In short, anything going to landfills is terrible; anything being recycled is better. This is quite obvious; however, exaggerating the issue with inner tubes going to landfills is this:
The exportation of plastic waste from developed to developing countries has dramatically exacerbated problems of marine plastic pollution. Plastic waste is in massive quantities exported from industrial countries to developing ones, and it is a known – but not much spoken about – fact that most waste shipped to developing countries is being openly discarded on land or leaks into river systems and the sea instead of being managed adequately through landfill, incineration or recycling.
In terms of biodegradability and toxicity, butyl is worst, and latex and TPU perform somewhat better. Latex biodegrades, so does plant-based TPU, and as opposed to butyl, it doesn’t contain any chemicals that interfere with endocrine and hormone systems, nor does it contribute to PH change in soil or water.
Regarding recyclability, the tube manufacturer Schwalbe has a recycling program for their butyl and TPU tubes. Whereas butyl rubber can be (beneficially) recycled back into material for new tubes and tires, recycled TPU can not be used again in inner tubes. Instead, it is downcycled to make sealing or insulation material. This is slightly less desirable. However, since even the valve stems are made out of TPU, these can be recycled together with the tube. As for latex, I could not find any information about the recycling of latex inner tubes. In theory, natural rubber is recyclable to some extent, but that does not help if no recycling program is available. Ultimately, the best solution is to patch your tubes and keep riding them.

Other things to consider:

• Durability: There are reports on TPU tubes’ weakness centered around its valve. Some reports on delamination, and then some reports on the thread which is in TPU and not metal, becoming worn out. As for Latex tubes, one weakness is their degradation under contact with UV, ozone, and oil. Once they are mounted, this is less a concern, but it is one when they are stored.
• Tube/tire sealant: Cannot be used with TPU tubes
• Re-using tubes: TPU Tubes can only be reused with tires of equal width or wider than the previous one (this has to do with the limited elasticity of the material)
• Inner tubes and rim brakes: Some TPU tubes are not compatible with rim brakes (especially with carbon rims) due to concerns with heat resistance. See details in the market overview below. Latex tubes are not recommended on carbon rims with rim brakes either.
• TPU tubes apparently typically slowly leak air and do not burst explosively like latex tubes often do, and on some occasions, butyl tubes do as well.

Summary

If you like durability, cheap cost, and ease of use, butyl tubes are practical. If you go for the lowest rolling resistance and don’t mind pumping before every ride, then use latex. If you are interested in the lowest weight, low rolling resistance, can afford to spend more, and are willing to take some risks and teething pains attached to new technology, then TPU tubes are for you. Here’s the combined assessment of all seven characteristics of the three materials:

Market overview

There are currenlty 4 performance TPU tube brands on the market, Tubolito, Revoloop, Schwalbe Aerothan and Pirelli.
Update #1 February 2022: Italian company Barbieri has introduced TPU tubes, called NXT, made in Italy. They are bright green with a black valve (non-removable core) and look similar in specs to the other four but are much better priced at EUR 16.90. There are no reviews or testing data available, so it’s hard to tell how they perform. I have added them to the overview below. Update #2 September 2022: Vittoria have included one TPU inner tube for road, the Ultra-Light Speed tube. It is made in Germany, and the little information they make available suggests this tube possible is made in the same factory as Revoloop’s products.
Wolfpack is selling TPU tubes on their side as Wolfpack TPU, but these are just Revoloop ones. The Pirelli ones are very similar to Tubolitos and seem to be made in the same factory. Then there is the Taiwanese company FOSS which has been having TPU tubes for a long time in its line-up. However, their tubes are less performance-oriented and more targeted toward the casual cyclist, with the selling point of being more environmentally friendly. Check them out of you like, but I don’t list them here, as due to their different approach, they do not show all the same characteristics as the other TPU tubes.
Generally, when picking a TPU tube, there is the following to look out for:

• Size: TPU tubes do not expand as much as butyl or latex tubes, so it is essential to buy the right size
• Weight: There are regular and ultralightweight ones. As with all materials, as weight decreases, so do rolling and puncture resistance.
• Price: albeit all are expensive, there are differences.
• Rim brake compatibility: Not all TPU tubes are approved for rim brakes
• Valve length
• Valve type: Some tubes have removable valve cores, some don’t. This can be important if you have valve extenders that need you to take the core out.

Update #3: For those on tubulars, you don’t have to miss out on TPU’s performance properties either. The Pirelli P Zero Race SL tub that was launched ahead of 2021’s Giro uses a TPU inner tube which comes in at 275g, 35g lighter than their previous generation P Zero Race tub.