Have you ever wondered which tubeless sealant works the best? We’ve carried out controlled tests to try to find out.
Read on, or watch the video below to find out how we did this, and discover which products came out on top. But first, a little bit of sealant theory…
What is tubeless sealant?
Tubeless sealant is a liquid designed to plug small holes in a tyre’s casing, thus preventing punctures. It works a bit like blood clotting to prevent bleeding. There are two main types — latex-based and latex-free.
Most sealants use the coagulating properties of natural latex to clog punctures. Latex is a dispersion of polymers (long chain molecules) in either water, or a water-based solution of ammonia. Inside a hole in the tyre, the air pressure drops and there is a rush of air. This causes the water/ammonia-solution to evaporate, leaving the latex molecules to coagulate (knit together), plugging the hole.
The problem with latex-based sealants is that, as air is pumped in and out of the tyre during normal use, the water/ammonia-solution slowly evaporates. This causes the latex to coagulate inside the tyre carcass, resulting in a dried-up mess, which after a few months, won’t seal punctures.
Most latex-based sealants also contain small particles, such as glitter or small fibres, suspended in the liquid. These help to provide a surface for the latex to coagulate around (like how snowflakes form around a particle of dust), thereby helping it seal holes more quickly and effectively. The downside is these particles accelerate the rate at which latex coagulates inside the tyre, reducing its lifespan.
These have no latex and no chemical change occurs inside the tyre. Instead, they rely on a more viscous (thicker) liquid, containing a wider variety of sealing particles, designed to physically plug punctures. These last far longer inside the tyre, but, in our experience, don’t plug punctures as well.
How we tested
The problem with real-world testing is that it’s impossible to test each sealant in the same conditions. The tyre, temperature and the type or position of the puncture all affect the sealant’s ability to seal. Therefore, we performed comparative tests in our workshop, controlling the variables as much as possible.
All the tyres needed to be identical, as the tyre casing makes a big difference to its ability to seal (generally, thicker casings seal more easily). Worn-out tyres may not seal the same as brand-new ones, so we had to use box-fresh tyres for all sealants.
In an ideal world, we would have used a different tyre for each sealant, but this would be extremely wasteful. Instead, we used two of the same model of tyre (Michelin Wild Grip’R 2), and tested three sealants with each tyre. (Please note that the tyres shown in the video are not the tyres used in our tests.)
After we’d finished testing a sealant, we thoroughly cleaned the tyre with water and rags, plugged the existing holes in the tyre with tape, and tested the next sealant on a different section of tyre. Using this method, we can be fairly confident that the order in which the sealants were tested didn’t affect the results.
After thoroughly shaking the bottle of sealant, we installed 100ml of each into the tyre (27.5in x 2.3in), inflated to 30 psi, then span and shook the wheel to ensure the tyre was evenly coated.
We then stabbed the tyre on the outer casing, between the tread blocks, using a 2mm pick. The tyre was spun until the hole was sealed and the pressure loss was then measured, before re-inflating to 30 psi.
The same hole was widened by inserting a 4mm screwdriver, and the process was repeated. We then tested with a 6mm, then an 8mm screwdriver, or until the tyre would no longer hold 30 psi.
We also inserted a 2mm pick halfway up the sidewall of the tyre, spun the wheel in the vertical plane, and measured how much air was lost from our 30 psi starting point. This test was intended to see how easily the sealants could access the harder-to-reach parts of the tyre.
Those which could seal the biggest holes, or hold the most pressure with a given size of hole, were deemed to perform the best.We also considered cost per unit volume when scoring and ranking the sealants.
The limitations of our testing
However, we should acknowledge the shortcomings of this protocol. First, due to the demand for destruction of brand-new tyres, we weren't able to repeat the test with the sealants in a different order, or to allow a fresh tyre for each sealant. This limits the reliability of our results, and so if someone else were to repeat this test, they may get different results.
Also, the longevity of these sealants was outside the remit of this test. This is because, to make a longevity test fair, we’d need to leave each sealant inside (six) different tyres for several months before testing. Again, this would demand the destruction of too many tyres. Simply using the sealant on a bike for a few months would introduce too many variables, as not all sealants would be used in the same way.
Finally, a sealant’s ability to seal a hole made by a cylindrical screwdriver may not necessarily correlate to its ability to seal a real-world puncture, such as a rip in a sidewall. We used screwdrivers and picks as they produce measurable and repeatable holes. As is often the way with product testing, we compromised realism for repeatability.
Best tubeless sealant results
Stan’s No Tubes Race Sealant
- £32/$39 for 946ml
So good: Simply put, this is the most effective sealant here. It plugged holes made by a 6mm-diameter screwdriver with minimal fuss, only losing 5 psi from the starting pressure of 30 psi, and holding 30 psi after sealing. The relatively runny solution sealed sidewall holes quickly too, and all punctures were plugged with minimal leaking. It was the only sealant to plug a hole made by an 8mm screwdriver, which it managed after three rotations of the wheel.
No good: It’s considerably more expensive than Caffélatex, which performs almost as well. We’d recommend Stan’s Race sealant for keen racers or regular tyre-rippers, but Caffélatex for more cash-conscious riders.
- £20/$28.99 for 1 litre
So good: This is certainly the best value sealant here. It’s one of the cheapest, but in our tests, it was the second most effective. The low-viscosity foaming solution plugs hard-to-reach sidewall punctures with the least air loss, and sealed holes made by a 6mm screwdriver with 10 psi air loss, and sealed 30 psi with minimal leaking once the hole was sealed.
No good: It couldn’t plug the 6mm hole as quickly as Stan’s Race sealant, and couldn’t plug the hole made by an 8mm screwdriver — only Stan’s managed that. Additives are available from Effetto that are claimed to increase the effectiveness of Caffélatex with larger holes, though.
Orange Seal Endurance
- £16/$16.49 for 237mm (with injector)
So good: We found Orange Seal’s original formula to be one of the most effective solutions for sealing large holes in the past, but it degraded quickly. This Endurance version is claimed to last up to four months between top-ups. The included valve injector makes topping up the tyre easier.
No good: Although it plugged sidewall-holes well, it couldn’t match the original version when it came to larger holes. After successfully sealing the hole made by a 6mm screwdriver, the seal broke as it was re-inflated above 20 psi. It’s the most expensive by volume too, and the 910ml refill bottle is barely better value, at £40.
Schwalbe Doc Blue
- £21 for 500ml
So good: Doc Blue is made by Stan’s NoTubes. While we’re not sure if it’s exactly the same formula, it performs just like the original Stan’s sealant (not the Race sealant we have tested here) in our tests. The only real difference is the blue colour, and the fact an empty 60ml dispenser bottle and a valve-core remover are included, making installation easier.
No good: It’s considerably more expensive than the original Stan’s solution on which its based (which costs £16 for a 473ml bottle). Like Stan’s original sealant, it performs well with smaller holes, but doesn’t plug larger ones as well as the top performers here. The 6mm screwdriver resulted in almost all the air being lost.
e*thirteen Tire Plasma
- £19.95/$17.95 for 1 litre
So good: At under £20 for a litre bottle, this is (just about) the cheapest sealant on test. It was able to plug up to 6mm holes quickly, with similar pressure-loss to Orange Seal Endurance Sealant. It was similarly mid-pack when it came to plugging sidewall holes too.
No good: It must be shaken vigorously then poured immediately for the small particles to get into the tyre. Although it coated the tyre well and plugged holes quickly, it never completely sealed them. When testing with a Michelin Wild Grip’R 2, the holes we made all leaked very slightly (like a slow puncture) after sealing.
Finish Line Sealant
- £15/$15 for 240ml or £40/$40 for 1 litre
So good: Finish Line claim its Kevlar-based sealant won’t degrade over time like latex-based sealants do. They say it will last the lifetime of the tyre, but we’ve not had time to test it for that long.
No good: In our tests, the gloopy solution was reluctant to coat the tyre, making it harder to seat the tyre than with other sealants. Once set up, it was the slowest to seal sidewall-punctures. It also performed worst in our outer casing puncture tests; it was the only sealant that failed to seal the tyre at all after it was stabbed with a 6mm screwdriver. The 240ml bottle is only enough for two tyres and it’s expensive per unit volume.
"Why haven’t you tested sealant X, Y or Z?"
We tested six more sealants last year using a similar method. You can find the results of that test here.
- 6 of the best: tyre sealant — 2017 testing
There are other sealants that we left out of this test simply because we’ve found them lacking in day-to-day use. For example, we’ve regularly tested Peaty’s Tubeless Sealant, and often found the viscous solution failed to coat the tyre properly, resulting in several sets of new tyres deflating overnight even after being shaken vigorously or ridden home.
Of course, there are other sealants that we simply haven’t got round to testing yet, but we’re working on it!