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In the modern world of cycling, technological advances have paved the way for numerous innovations. I’m talking disc brakes, fully integrated cable routing, electric shifting and, finally, tubeless. The latter is probably one of the most significant developments in recent years. But what exactly makes it so attractive and are all aspects of it really positive? In this article we dive deep into the pros and cons of the tubeless system and analyze in particular the tubeless sealant as well as tubeless kits to convert to the tubeless system.
I use my experience of tubeless on road bike, gravel bike and MTB to illuminate all possible points of view in this post all-around. Hazards and Ecological aspects as well as compatibility with different applicatios of tubeless are covered here just as well. In addition, I am specifically testing three tubeless products: Stan’s Notubes (identical to Schwalbe DocBlue), Finishline Fiberlink (tubeless milk with Kevlar particles) and a more ecologically friendly variant: Végétalex.
Which sealant spills the milk, literally? Let’s find out.
The best tubeless tire sealant
You are here just for the results? Good! Let’s see which sealant has the best sealing properties. Let’s keep it short: I tested the following three products. The cuts in the tire were about 4mm in size. Each agent had 24 hours to close the hole in the tire.
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You can find the detailed test and presentation of the products below. Where I also address all the aspects of a good tubeless sealant such as chemical ingredients, test results in detail and ecological footprint, in the truest sense of the word. As sometimes the sealant leaks and is left on the trail behind.
However, the realization that all products want to be able to plug holes up to 8mm, but in practice this looks quite different, was grave. I’ve gone into more detail below about how I set up my test and the unfruitful result.
Surprisingly, the 4mm cut was not closed by any agent in the test. My guess is that it’s a question of exactly how you define the cut and its size. If you pierce the tire with an 8mm mandrel, it is not the same as a straight cut of exactly 8mm length, ie. with a knife or flint stone. This is because the mandrel primarily stretches the tire; once it is out, the elastic material closes again somewhat, and the sealant only has to do part of the work.
So much for the short result. You can find the complete test protocol below.
A brief overview of tubeless
“Tubeless” means, as the name suggests, without a tube. Instead, the tire is mounted directly on the rim and sealed with a special chemical fluid, the sealant, to prevent air pockets. This system has become particularly popular for mountain bikes, gravel bikes and, more recently, road bikes.
The advantages of tubeless systems
- Puncture safety: One of the main reasons for switching to tubeless is the significant reduction in puncture risk. Eliminating the hose prevents “snakebite” mishaps (caused by the hose getting pinched).
- Performance: The absence of a tube allows the tire pressure to be dropped, resulting in better traction and therefore improved performance, especially off-road.
- Weight: Although the difference is minimal, riding without an inner tube can mean a weight saving, which is particularly interesting for road cyclists.
The disadvantages of tubeless systems for bicycles
- Installation complexity: Installing a tubeless tire can be a real challenge, especially for beginners. Patience and sometimes special tools or parts are needed here to make installation easier.
- Maintenance: The sealing agent must be renewed regularly, and it can happen that it clumps inside the tire. Better said: it is only a matter of time when this clumps. Removing the remnants from the tire may sometimes be necessary if the tire no longer closes flush with the rim due to the bumps.
- Price: Tubeless-compatible tires and rims are usually more expensive than standard components. See tubeless kits below – several components are usually necessary, all of which contribute to the price.
- Tightness: Tubeless tires have more often the tendency to lose air. The vast majority of users (whether from communities, experience reports in blogs or YouTube videos) complain about losing air and hence pressure loss after a short period of time. From 24h to 48h, the tire loses air pressure significantly and must be pumped back up more often. However, this is more of a random component, some combinations hold air better than others, but it is not reproducible. The same rim and tire combination can work in the front but not in the rear, it is quite common actually. Unfortunately, there’s little you can do about it other than completely remount the tire with new rim tape, if you have the leisure. Even then, however, it remains a gamble how well the tire is sealed afterwards.
My experience on tubeless – road bike, gravel bike and MTB
During my 10+ years on the bike I had the chance to put quite some tires on without an inner tube. Mostly out of my own curiosity, sometimes with more sometimes with less success. Briefly summarized, one can sum up as follows:
- Road Tubeless: In the linked post I have given several updates on the subject. Nowadays, I also trust the narrower tires without a tube. Even setting up does not necessarily have to end in disaster, but it can. The Ötztaler (Tyrol, Austria) marathon of 225km with over 5,000 meters of altitude and corresponding descents at over 80km/h were put to test my Tubeless Conti GP 5000 S TR. Which they passed flying.
- Gravelbikes: I’d count all my road bikes with 38mm+ tires among them. Here I have virtually no problems at all with tubeless setups. Only old tires that are particularly worn can sometimes no longer be patched with the tubeless sealant alone. Which is perfect for my test to put the tubeless products to the toughest test possible.
- MTB: I have the least experience with this genre, only one of my bikes falls into this category and there I could put the wide tires on tubeless without any problems. There were mixed results here as well: one tire was perfectly tight and lost virtually no air. The other tire was less dense and had usually lost more than half of the pressure after a some days passed.
My general conclusion on tubeless in total is positive. I like to ride tubeless on all the bikes. Though on the road bike I just as gladly would pick TPU inner tubes, as the simplessness of an inner tube just has it’s own appeal.
To be open with you: Tubeless tires can be quite a mess.
Well and good, my tire suddenly deflates in the test and leaves a latex pool on the floor. Left and right also little splashes spatter further into the room. I did have a “secured” area set up with a mat, but the photo above is a spontaneous latex outpouring. You just can not trust a tubeless tire in such a test.
If you ride tubeless you must be prepared for such messy outcomes. Also less nice is that the sealant spreads with every turn of the tire on to the frame in case of a cut. Cleaning the bike becomes an even bigger struggle, because the sticky nature of the sealant is particularly stubbornly stuck to the frame and binds a lot of dirt to itself.
Inner tubes as a fallback
Although it is often said that you should also have a spare inner tube for emergency handy. That is when the tubeless tire can no longer be cured by sealant alone. But this is probably more theory than practice. Opening the tire on the road, draining the sticky latex mixture and inserting an inner tube is not a nice thing to do. Neither for the environment nor for the then dirty hands. The new tube will form a unit with the latex residues in the tire and stick.
Much better and more practical is to fix the defect with tubeless patches or so-called tubeless “worms” (plugs). On the road, you can use the plugs, smaller the puncture with them and let the tubeless sealant do the rest.
It all sounds a bit more negative than it really is. If you do not want to change the tires frequently and the wheel is moved frequently and to re-pump the tires more often times is not a problem to you, then you will have a very good time with tubeless. Because the puncture resistance is a big plus.
Before we continue with the tubeless sealant test, I would like to briefly discuss the different products and their advantages and disadvantages.
A deep dive into the milky tubeless world
The most important component of the tubeless kit is the sealing milky chemical, often based on latex or natural latex mixed with ammonia. As a tubeless rider, you need a permanent supply of sealant, because you have to regularly refill the tires with the agent. As a rule of thumb, you should refill once or twice a year. The sealing milk ensures that tire and rim form an airtight unit during mounting. But the sealant also ensures that the tubeless tire is so extremely puncture-proof. If the tire is punctured by a sharp object while riding, you can sometimes observe how the sealant goes into action and seals the hole. First it sprays some sealant and after a couple of turns of the tire it is gone.
However, not all product compositions are even quite the same. Depending on the manufacturer, there can be considerable differences in the chemical composition of the liquid. Therefore, as an experienced bike hobbyist, it makes sense to buy the sealant for a particular bike individually. Components of the milk must certainly be critically evaluated, which is why I had already tested biodegradable sealant (see below).
Chemical ingredients and ammonia in the sealing milk
A popular point of contention when choosing a sealant is the ammonia content, which is present in many sealant grades. Allegedly, the ammonia is not so good with some bicycle tires or with carbon rims and lead to the decomposition of the tires or rims. Maxxis also directly advises against using sealant containing ammonia: Link to maxxistires.com.
However, there are also an overwhelming number of testimonials from cyclists who use ammonia-based sealants and ride without any problems. The points of compatibility with tires makes me personally no cause for concern. The ammonia in the sealing milk is a natural component of the latex and the total percentage of ammonia in the sealing milk is negligible (often less than 0.1%). The ecological aspect is much more important to me.
Revosealant sealing milk from Continental, for example, does not contain ammonia. The Végétalex presented below also uses a completely different carrier than natural latex.
In summary, this special milk used in the tubeless system consists of several components. Their main task is to immediately seal minor holes and cuts in the tire.
- Ingredients: Most tubeless fluids are based on synthetic or natural latex or synthetic polymers. This allows the fluid to solidify quickly upon contact with the outside air, sealing the hole.
- Additives: Many manufacturers also add small particles such as cork, plastic, Kevlar, carbon fibers or even ground olive pits to their milk to seal larger holes more efficiently.
- Ecological aspects: Newer products on the market, such as those from Effetto Mariposa, are biodegradable and rely on natural ingredients. The goal here is to minimize the ecological footprint.
Latex or natural latex is generally a biodegradable material. However, additives as well as the possibly contained ammonia do not make the mixture environmentally friendly. Unfortunately, very few manufacturers specify whether ammonia is included and in what concentration to keep the latex liquid. Because without ammonia, the mix would not remain liquid.
Végétalex sealant has a completely different carrier: polysaccharide as a carrier solution containing only biodegradable substances to seal even larger holes.
Other manufacturers are far less transparent and do not specify exact ingredients or even ammonia content. Likewise, I could not find a bicycle print magazine that would have dealt in depth with the ingredients.
Briefly: Potential hazards and pollutants
- Chemicals: Some tubeless sealant products may contain harmful chemicals that can cause allergies. It is important to wear gloves and avoid direct skin contact when handling these products. Ammonia has a strong odor and can irritate the respiratory tract.
- Environmental impact: Not all tubeless milk products are biodegradable. Some may have harmful effects on the environment if disposed of improperly.
If you use CO2 cartridges to inflate the bicycle tire, you should make sure that the sealant is compatible with it. Depending on the sealing product, the use of a CO2 cartridge can cause the sealant to clump and become unusable. This happens because the chemical foams up due to the extremely high pressure and the gas of the Co2 cartridge.
Some products like this SKS sealant is also compatible with CO2. The tubeless kit from SKS includes this sealant, but you can also buy them separately. There are also some other products that advertise being compatible with Co2 cartridges. If this is important to you, then always pay attention to this information. In case of doubt, it must be assumed that the milk is otherwise incompatible.
Three popular tubeless milk products compared
I made a heavily worn gravel bike tire (a Gravelking Semislick in 700x38C) the guinea pig for my test. The tire already has several larger cuts of 2-4mm. According to the manufacturer, all of the following products should be able to seal these holes.
- Finish Line – Fiberlink: A premium product that advertises a sophisticated formula. It provides an excellent seal and is known for its durability.
- Effetto Mariposa – Végétalex: A greener option. As mentioned earlier, this product is biodegradable and uses natural ingredients without compromising performance.
- Stan’s NoTubes: One of the best known products on the market. It provides a reliable seal and has proven itself over the years.
Test procedure and result
The test tire is cleaned after each run. The holes or cuts in the tire are 2-4mm in size. The air pressure for the 40mm wide tire (40-622 or 700x38C) is brought to 4.5bar. This is about the optimum air pressure for a rider of about 85kg for such a “narrow” tire.
Each product has 24h to seal the holes. Tubeless plugs are not used (during the test). After 24h, the tire is inflated again to 4.5bar and it is checked whether the holes have been sealed in the long term.
The tire was already worn and “by nature” already had several cuts of a length of about 4mm. When pumped up to a pressure of > 50PSI the tire always cracked and the air was lost. In some test runs even the complete sealant load (tire all filled with 60ml) just leaked empty.
This is very frustrating and a real mess. Anyone who wants to convert a worn tire to tubeless should therefore be careful. It could end up in a sticky pool in the workshop or, in the worst case, in the living room, if you happen to open your workshop there.
I finally got the hole sealed, but only for the help of a tubeless plug. And even then, a lot of sealant has been injected into the workshop.
Let’s briefly discuss the products in detail in the final conclusion.
Végétalex – Biodegradable sealant
The product with the greatest transparency in the test. Effetto Marioposa from Italy is the only manufacturer to specify what exactly is used as a carrier and further ingredient.
I had already tested the product extensively years ago. You can find more details in the test:
Here I would like to report only briefly the result.
Test result sealing: all but the largest cut (4mm) were sealed. Even after 24 hours and repeated inflation, air escaped from the larger cut.
1 out of 3 stars:★☆☆
Ecological footprint of the product: Very good. Relatively close manufacturing site (talking from a perspective of Europe) as well as transparent ingredients, completely biodegradable.
3 out of 3 stars: ★★★
Considered the inventor of the tubeless system on bicycles, Stan Koziatek is still going strong today. For many, Stan`s NoTubes is the epitome of tubeless. Schwalbe also has the DocBlue developed and bottled here, presumably with the same or nearly the same formula. However, the exact ingredients are a company secret.
By the way, if you want to read more about the invention of tubeless, in the “Prime Mountainbiking” issue 15-2018 is a detailed interview with Stan:
Simply read the magazine online with Readly – with full access to all current issues and archive:
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Here, briefly, are the results for my test of Stan’s NoTubes sealant.
Test result sealing: all holes except the largest cut (4mm) were sealed. Even after 24 hours and repeated inflation, air escaped from the larger cut. As a result, this is unfortunately also unsatisfactory.
2 out of 3 stars:★★☆
Ecological footprint of the product: Exact statement of contents is missing, ammonia content not indicated on product.
1 of 3 stars:★☆☆
Finish Line Fiberlink
I had already written about an earlier version of the product. Meanwhile, the name as well as the label has been redesigned. But one ingredient seems to have remained the same so far: Kevlar. These fibers should help close the larger holes.
But a key part of Finish Line’s advertising slogan has been dropped: refilling fresh milk. Until now, the US manufacturer had strongly advertised that its tubeless sealant did not need to be topped up year after year. It was supposed to last the life of the tire. I was never able to disprove this in the end (after about 1.5-2 years, the milk was still liquid in my long-term test). Currently, however, the Fiberlink mixture is sold without such advertising. According to the packaging, the product offers “optimal longevity between refresh cycles.”
Result: best result in the test, as the only sealant in the test, the FiberLink also cut a good figure at 4mm but after 24h also not completely sealed.
Sealing test result: all but the largest cut (4mm) were sealed. Even after 24 hours and repeated inflation, air escaped from the larger cut.
2 out of 3 stars:★★☆
Ecological footprint of the product: Exact statement of contents is missing, ammonia content not indicated on product. Only “natural latex” is named as content and Kevlar as additional ingredient. Unclear if biodegradable, very likely not.
1 out of 3 stars:★☆☆
The tubeless system offers numerous advantages for cyclists, especially in terms of puncture resistance and performance. However, there are also disadvantages and challenges, especially in terms of installation and maintenance. It is also important to be careful when using tubeless milk and be aware of the possible effects on the environment and health.
While the future certainly holds many innovations in cycling technology, the tubeless system has already made a lasting impression and is considered by many to be the gold standard.