Mounting a tire without an inner tube, aka tubeless, is the fastest choice in almost any condition. You are looking into saving around 7 watts over classic butyl! If tubeless is not a possibility, latex tubes are always an option and almost as fast. The newer TPU tubes can be produced with very little material and are a little faster than the classic butyl. An excellent choice for repair bags. Good, old black butyl tubes still present the time-tested and cheapest option.
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What are my options for mounting road tires?
Currently, there are three distinct options for mounting a pneumatic tire onto a bicycle wheel rim: tubular, tubeless and clincher. The latter refers to using an inner tube.
- Tubular: The tire is shaped like a tube and glued onto the rim. It’s cumbersome, requires a lot of work, and is not even faster than modern clincher setups. It won’t be covered here since it’s rarely used.
- Tubeless: as the name suggests, mounting the tire without an inner tube, mostly combined with a liquid inside, a sealant, which serves to make the tire airtight and also offers some self-repair in case of a puncture.
- Clincher Butyl tubes: the classic, black tubes made of synthetic butyl rubber
- Clincher TPU tubes: newer tubes, often color or translucent, made of thermoplastic polyurethane
- Clincher Latex tubes: you guessed it, made of latex and often in pinkish or pastel-like color
If you are looking for extensive coverage of bicycle tire topics, this video from GCN is recommended.
How do these options compare and which one is fastest?
They set out to answer precisely this question using our favorite Continental GP 5000 S TR tire with a different set of inner tubes as well as tubeless. Below is the graph with the rolling resistance testing data at 100 PSI, 80 PSI and 60 PSI. The lower the line, the less resistance; thus, the setup is faster. Notably, pressures between 60 and 80 psi are probably the most realistic in current setups with 25-30mm road bike tires.
- Tubeless is the fastest option with the least rolling resistance. In this test, 20 mL of sealant was used.
- Latex is the second fastest choice material. Vredenstein Latex is only 50g and thus a little faster than the Vittoria Latex at 80 grams. Of note, the Vittoria is also faster than some much lighter TPU or butyl tubes despite being heavier, which shows an inherent material advantage of latex (s. video below).
- TPU does not seem to be very different in terms of properties of the material over butyl, but because the TPU tubes can be constructed very light and thin (about half the weight of butyl) there is less energy loss and they tend to be a little faster.
- Butyl tubes are the heaviest and slowest at 105 g for the popular Continental Race28. However, the thinnest butyl tube, Continental Race28 Light, tests even a little faster than the much lighter Tubolito Road, which weighs only 39 g. This again suggests that TPU does not have an inherent advantage over butyl when it comes to the material used.
Aerocoach testing verifies the rolling resistance data
In another blog post, Aerocoach, a renowned company in this field, provided effectively the same data when they tested a series of inner tubes. The testing protocol was done on rollers, and you can see that the watt numbers are roughly twice the value for Bicycle Rolling Resistance due to a different setup and losses in the whole drivetrain. This is arguably more realistic, but we mostly care about the relative order, not those absolute numbers.
Again, Latex is the fastest, TPU follows and butyl is the slowest. Beyond that, as expected, lighter tubes are faster. In their test, however, the Tubolito Road TPU tubes appear to be slower than Schwalbe Aerothan TPU at a similar weight, yet a little faster than the Continental Race28 Light butyl tire.
In their conclusion, they add an excellent perspective stating that the lightest TPU inner tube, the Revoloop Ultra Race, would only be faster than its latex competitors if the gradient reaches over 15%!
TPU inner tubes like Revoloop, Tubolito, or Aerothan have the weight advantage, but it’s only really noticeable on gradients over 15%. If you want the fastest option, think about going tubeless, and keep TPU for repair kits.
Going tubeless can save you about 7 watts compared to traditional butyl tubes. If that’s not an option, consider using latex tubes, which are equally fast.
Why is tubeless fastest?
As discussed in another post, a faster tire has minimum energy loss when undergoing compression and decompression cycles while rolling along the pavement. When including a tube, the friction between the tube and the tire creates an additional energy loss compared to tubeless. In general, the less material, the less energy is lost. That’s why thinner tubes generally will be faster but offer less puncture protection! Another aspect is how much energy the tire and tube combination returns after being compressed. The more it returns, the less energy is lost and the faster the system is. It is again all down to the hysteresis of the material, as the video below illustrates.
Latex inner tubes are almost as fast as tubeless. Why? Latex returns 75% of the energy compared to 20% of standard butyl tubes. Less energy lost and hence faster!
When should I not use tubeless?
There are a couple scenarios where tubeless may not be the best choice:
Latex is the fastest option for Track Cycling
Using latex is your best option when you want a clean and fast solution without the hassle of mounting tubeless. The only disadvantage is that air is lost quickly at about 1 PSI per hour. This means you must pump before every ride, which can be especially difficult on multi-day events. In terms of product, judging from customer feedback at the big distributors, the Vittoria Competition inner tubes seem to be better built and with the consistent quality compared to the Vredestein Race Latex.
In track cycling. Just imagine having a puncture and spaying sealant all over the track! You may never show up in that velodrome ever again. It’s probably also forbidden. That is the ideal case for a latex tube, as sessions are short and you can easily repump the tires. Tubulars are still prevalent in this discipline, as they can resist high pressures and do not come off the rim easily. Still, nowadays, more and more people are switching to latex.
Light and packable TPU tubes shine in repair kits
As a spare, the TPU tubes have their place in the gear kit. They are the lightest and pack the smallest. However, looking at the comments around the internet and experience from the local community, the thin TPU tubes seem prone to blowouts and punctures independent of brand, which doesn’t make it a great choice beyond that purpose. As such, it is probably advisable to go for a little “beefier” option, such as Revoloop Race (39g) or Schwalbe Aerothan (41g), as the absolute minimum rolling resistance is not the most essential criterion in this scenario. And yes, besides tubeless plugs, it is recommended to always bring a spare tube as a means of “last resort” on a tubeless setup.
The Continental Race28 is a popular and affordable option for the classic tube scenario. It appears to be faster than the Schwalbe SV20 Light and is probably more puncture-resistant than either light version. If you really care about the least rolling resistance, you would want to switch to tubeless or the other options better.
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