Tire Sealants

May 15, 2012

Use of tire sealants, while well established and common practice in the mountain bike world, is still a relatively new concept in road-based cycling and triathlon. To newcomers, it can seem like a black art. With so many brands, different types, application amounts, riding conditions, wheel and tire types, what should I use, if anything? This article attempts to cover the market of tire and tube sealants, and distill the information in to what really matters for most triathletes.

What many are now realizing is that the use of a sealant can apply not only to tubeless clinchers, but also tubular and tubed-clinchers. The key premise being: While it can’t guarantee you won’t puncture, it is cheap insurance that has a good chance of saving your race. At this time, it appears that the rolling resistance geeks are largely agnostic on the topic—there is no measurable change in Coefficient of Rolling Resistance (Crr). All it costs you is a little bit of weight. Weight that is, in my estimation, well worth carrying around.

There are two main types of sealant that are sold today:

1. Preventive sealants: intended to be applied to the tube or tire before riding.

2. Emergency sealants: intended as an on-the-road “fix” after a puncture has already occurred.

In general, most of the preventative sealants require that you remove the valve core from your valve stem to inject it. These sealants usually have some sort of particulate (or sealing “chunks”) suspended in liquid. The particulate is intended to clog holes (for example, when you run over that thorn). However, it also means that it would clog your valve stem if you try to inject it while the core is still intact. The emergency-style sealants are of a thinner solution, and will inject through the valve core.

The one caveat that tends to plague sealant’s application to road-based cycling is the nature of the tire system: low volume and high pressure. For the sake of example, let’s pretend that you run over a thorn. Most sealant manufacturers recommend that you use around one or two ounces of sealant in a road-sized tire. This means that the sealant does *not* fill up the entire volume of the tire. As you run over the thorn, it will take a moment for the sealant to roll around inside the tire and “find” the hole. Since road tires use relatively high pressure (say, 100 psi or 7 bar), there is a chance that you’ll lose a fair amount of this pressure during the time it takes to seal. And that, my friends, is the crux of it all—and what is making sealant manufacturers scramble to find the best possible mixture. For mountain bike applications, pressures can be as low as 20 psi; when you hit that thorn, the difference in atmospheric pressure between the tire and the ambient air is not as great, so you do not tend to lose as much pressure while the sealant works its magic.

As well, the performance of a sealant isn’t necessarily the same for each type of tire (tubular, tubed-clincher, and tubeless clincher). In general, sealants live the easiest life in a tubeless application. When that puncture happens, there is only one layer of material that must be sealed. With a tubular or tubed-clincher, there are two separate holes to fill: one in the inner tube, and one in the tire casing itself. This is compounded by the fact that the two layers of material move independently of each other. As you roll down the road, the tire and tube get deformed (by the road), and then bounce back to a round shape with each wheel revolution. That extra bit of movement between the tire and tube makes the sealant’s job tougher. This isn’t to say that sealants don’t work at all in these applications, just that they likely won’t have quite as high a degree of effectiveness (regardless, I’d still recommend using a sealant).

It should be noted that if a puncture does happen, and get sealed, it is prudent to inspect the tire at the end of your ride. The idea is to allow you to finish the ride or race, but that does not assume indefinite safety or robustness of the now-damaged tire. Mountain bikers will sometimes find a thorn or other object stuck in their tire at the end of their ride and have no idea how or when they picked it up. With a tubed-clincher, you may want to replace the tube, even if you think the sealant did its job. Tubular is 50/50; the extra expense of money and time for replacement can make it a toss-up. Tubeless tires have the highest probability of being able to continue life-after-puncture.

On to the sealants themselves, this is a non-comprehensive look at what’s available. It is non-comprehensive simply because the product category is expanding so rapidly. It seems that every other week a new product hits store shelves, and everyone wants in the game. Expect this growth to continue, and the products to continue improving.

Stan’s NoTubes Sealant
At least in mountain bikes, Stan’s is the standard. Founded by Stan Koziatek, this company sells a huge variety of products from tubeless-specific rims, tubeless conversion kits, complete wheels, tools and, of course, its famous made-in-USA sealant. As the name suggests, this latex-based sealant is largely intended for tubeless clinchers, and applies equally well to road, cyclocross, and mountain bike systems. The secret, Stan says, is in their formula and its “crystals”, or chunks. The mixture is liquid, similar in consistency to whole milk. It is non-homogenous, so the crystals settle quickly to the bottom. Like James Bond’s martini, it must be shaken (vigorously), not stirred.

There have been many attempts to copy this popular product. For tubeless applications, there’s no doubt that it works quite well. In my personal experience, its effectiveness drops slightly as you go to tubular and tubed-clincher tires. But as previously mentioned, it is cheap insurance that might save your day and get you rolling back to transition with 70psi instead of zero. Stan’s is also one of the easiest to use. They have a great injector that works on removable-core, externally-threaded valve stems (for example, a Vittoria or Zipp tubular tire, or the very-common inner tubes from Continental or QBP). For non-threaded valves such as Continental tubular tires, Stan’s also sells pre-filled two ounce bottles can inject directly in to your valve – and is the exact amount that they recommend for a road tire.

The only downside to using Stan’s is the fact that it, like all other latex-based sealants, dries out over time. The rate of drying out depends largely on the ambient humidity in your region, and whether you’re using tubular, tubeless, or tubed-clincher. The longest-lasting environment is a humid climate and the safe-haven of a butyl rubber inner tube; the most precarious environment is a dry climate and poorly-sealed tubeless tire. This also presents a minor problem over time in the form of gummy valves. The sealant can gradually seep in to the core and can make threading/un-threading more difficult. Stan’s sells replacement valve cores for two dollars (US), so keep a few on hand and replace yours when they get sticky. They also have an ingenious and simple valve removal tool that makes the task done in seconds, but you can also use needle nose pliers.

Vittoria and Geax
Vittoria burst on to the triathlon scene several years ago, and in a huge way. What was the product? Vittoria Pit Stop. What does it do? It’s a portable version of “fix a flat”, an all-in-one sealant plus CO2 cartridge. The scenario goes something like this: Jane Triathlete is JRA (Just Ridin’ Along) at her local sprint tri. Then, without warning, psssssssssssssssssst! Flat tire. Bummer. But she came prepared with a Vittoria Pit Stop canister taped neatly under her bike saddle. Hop off the bike, open the presta valve, jam the Pit Stop on to the valve… and she is back on the bike and riding in less than 60 seconds, with 90 psi in her tire.

This product was such a novel concept at the time. You could buy peace of mind. And buy they did (and still do). The first few years the product existed, you could predict the sell-out time like clockwork before Ironman Hawaii. The island, the entire island, would run out of Pit Stop on Thursday night. And on Friday, the last-minute scramble ensued. Never mind the fact that these people had two spare tubes, a patch kit, and the kitchen sink on their bike. They wanted Pit Stop. It got to the point where sponsors of every type were buying Pit Stop ahead of time for their professional athletes. It wasn’t necessarily their bike sponsor or wheel sponsor’s job to provide this, but it was such a significant and relatively cheap value-add that they’d bring a box of it to the island.

This leads us to ask: Does it really work? In my personal experience, you’ve got about a 50/50 shot of sealing the puncture. The anecdotal evidence from working on a *lot* of professionals’ bikes is that it works better in tubulars than clinchers. That isn’t to say it can’t work on a clincher; this is just an N=1 data set. The beauty of the system is the simplicity, but that’s also the Achilles heel. The liquid is non-chunky and can inject straight through your valve core. But, for the most part, you want the chunks for sealing punctures. I predict that Pit Stop will continue to be a top seller simply due to convenience, but likely will not be the most effective sealant in all cases.

Vittoria does, however, offer another product under their Geax brand. For those unaware, Geax is their line of mountain bike products: Tires, tubes, and sealant. They have a line of tires and sealant called TNT, short for “Tube, No Tube”. As the name suggests, these tires and sealant may be used with a tube, or tubeless. The TNT sealant must be injected in to a removable-core system, and is intended as a preventative measure, vs. the emergency-only nature of Pit Stop. I’ve not yet used this sealant, but a little birdie suggested to me that it may, in fact, be one of the better products out there, and possibly be used by several ProTour teams for Spring classic races.

Effetto Mariposa Caffelatex
Effetto Mariposa is an Italian outfit specializing in a variety of cycling-related goodies. They started with a high-quality torque wrench set, but soon expanded in to tire sealants, tubeless conversion kits, lubricants, and even a carbon-frame-protecting adhesive tape.

Known as Caffelatex (its kit is pictured above), its sealant is quite unique in that it has a foaming mixture. The benefit, they say, is that it more quickly ‘finds’ a puncture, compared to non-foaming competition. In addition, it is claimed to better deal with sidewall cuts or punctures, since the centrifugal force caused by riding makes liquid-only sealants pool at the bottom of the tread. As well, Caffelatex is 100% ammonia-free, which makes it environmentally harmless, and generally harmless to any type of rim, tire, and tube. In fact, Dugast recommends this as the only sealant you should use with their tires, due to ammonia’s potentially harmful effects. While Caffelatex is relatively new to me, there seems to be a growing camp of people who use and support the product.

Effetto Mariposa also offers a CO2/sealant combination similar to Vittoria’s Pit Stop. It is called the Espresso injector, and can be used either as a preventative or emergency-type sealant. The key benefit of the Espresso injector is the fact that it has a flexible plastic tube that attaches to your valve stem. This allows you to effectively use the injector on a disc wheel valve cutout (the same cannot be said about most other emergency sealants). Even if you don’t ride a disc wheel, the Espresso injector is a worthy addition to your Ironman special needs bag.

Slime
Most of us are very familiar with this product; it has been available for many years on the shelves of your local big-box, home improvement, or hardware store. There are different mixes for automotive, small vehicle, and bicycle applications. In the past, it appeared as though Slime was perfectly content to maintain status quo as the “everyman sealant”: what other people buy, not us true athletes. It’s for the guy filling up his lawnmower tires.

More recently, Slime has impressed me with a push into new and improved products, and showing presence at more race expos and triathlon tradeshows. Gone are the old days of a single Slime formula and pre-injected Schrader-only inner tubes. Now we have a very legitimate player.

Specifically, you should be interested in their new Slime Pro. It is set to compete with Stan’s, Caffelatex, and all of the other latex-based, tubeless-specific sealants. Its mixture is less of a true green slime than the traditional product; it’s now more of a greenish-white-milky slime (getting hungry yet?). It’s non-homogenous, so you must shake it up. After that, you can use it exactly like any other sealant of this nature. Slime provides a plastic nozzle and tube for injecting your removed-core-presta valve. This system works, but the downside is that it’s harder to measure how much you’re injecting. I personally recommend using a graduated/measuring injector, such as the Stan’s or Effetto Mariposa products. Similar to just about every other sealant, Slime Pro will dry out over time. Plan on adding a boost of sealant every six months or so, depending on the humidity in your area.

What of the other Slime products? The automotive Slime is a thicker goop, and some prefer this for inner tube applications. In my experience, this is a decent way to go that won’t usually offer a permanent seal, but it could very well get you back to T2 without stopping. The thicker mixture will deal well with small punctures such as “goat head” thorns, small staples, etc. While the puncture might “weep” sealant and slowly lose some air pressure, the thick goop should make these losses minimal. Some mountain bikers will even mix a 1:1 mix of Slime and Stan’s, looking for the best of both worlds. My personal experience showed that this combination didn’t evaporate as fast as, say, pure Stan’s. However, it did not keep the bead sealed as well on my tubeless cyclocross wheels (I had to add air much more often compared with pure Stan’s). So I suggest its use only for inner tubes and tubular tires.

Hutchinson
Those who know Hutchinson know that they are big into tubeless. This company, partnering with Shimano, made the first commercially available road tubeless system (Hutchinson Fusion tires and Dura Ace aluminum wheels). What you may not know is that Hutchinson makes its own sealant products as well. Called Fast’Air, this is available as a ready-made “emergency” injector similar to Vittoria Pit Stop. They say it can work in all types of tires: tubeless, tubular, and tubed-clincher, for punctures up to 1mm in diameter. Hutchinson also sells a tubeless-specific sealant called Protect’Air, that must be installed via a removable-core valve stem. They claim that the proprietary blend will seal punctures up to 3mm diameter, and will last for two years without drying out.

Hutchinson also sells a unique repair system called Rep’Air. This is a glue-like substance that can repair cuts on the inside of your tubeless or tubed-clincher tire. For punctures up to 1mm diameter, simply use the Rep’Air glue by itself. There is also a patch kit that can be glued to the inside of the tire for punctures up to 5mm (!) diameter. This could very well save your tire and extend its life considerably.

The beauty of the Hutchinson product is that the Fast’Air cartridge can serve as an all-in-one installer for its tubeless tires. Depending on your luck, you may or may not be able to inflate your tubeless tire with a floor pump. There is always variance in manufactured goods; get unlucky with a loose fitting wheel and tire, and you may need an air compressor to ‘blast’ the tire beads in to place. For those of us who don’t have a compressor at home, a quick shot of Fast’Air will seat the beads and inject puncture-resisting sealant all in one step. Sure, it’s not as cheap as a floor pump, but neither is an air compressor.

Specialized Airlock
Similar to bicycle and auto Slime, Specialized offers a sealant specific to inner tubes or tubular tires. Also similar to Slime, it is available for sale in pre-injected inner tubes. Their proprietary blend is not intended to seal tubeless beads, likely due to its non-latex and non-drying formula. The good side of this is that it does not dry out quickly. The potential bad side is it may not offer a permanent seal to your puncture. In my mind this is not a deal breaker; the idea is to get back to your house or T2 without stopping, and change the tube later if need be.

The Specialized formula is fairly unique in that it is a completely homogenous mixture. No shaking or stirring, Mr. Bond. This means it’s generally a bit easier to install because you forego the frantic process of mixing and injecting… and hoping you’ve put the perfect mixture in each tire. It is worth noting that Specialized recommends using a higher volume of sealant than the competitors—roughly double at four ounces per tire. You can use Airlock in either latex or butyl tubes, so try it out for training or race day.

Flat Attack
You may not have heard of Flat Attack, but they market themselves as “The original green sealant – Since 1982”… and we’re here to tell you all about them. Flat Attack is a “semi-homogenous” mixture. It has a propylene glycol-base, and they tell us that it’s unlike any other sealant on the market. Benefits include: 1) It doesn’t dry out, 2) The chemicals and mixing method they use disperses the fibers evenly throughout the mixture, and 3) The lack of ammonia means it will last for years without rotting the inside of your tire or tube. They real key, according to Flat Attack, is the unique type of clotting fibers they use.

They claim that the product will last for 5 years, or the life of your tire or tube. Similar to the Specialized and auto or tube Slime products, it is not intended for tubeless applications—keep this for your inner tubes and tubular tires. As well, it is said to work for punctures up to 3mm in diameter, depending on air pressure and tire volume. For those who prefer a plug-and-play option, you can purchase pre-injected “Freedom Tubes”, with the appropriate amount of sealant already inside. Flat Attack also holds very high standards when it comes to environmental friendliness. They use food-based chemicals that are not harmful to people, pets, or the environment. We’ve obtained testing samples of this new-to-us product, and look forward to seeing how it fares long term.

Bontrager
Bontrager offers two sealants to choose from: Sealsafe (for inner tubes) and Super Juice (for tubeless applications). The former is a homogenous glycol-based mixture, which Bontrager tells us will not separate and is good for the life of your inner tube.

Super Juice is a separate beast. Like Stan’s, CaffeLatex, or Slime Pro, it may be used for either tubeless or tubed applications. However, those are all latex-based, and Super Juice is glycol-based (similar to Flat Attack or standard Slime). It stands as the only glycol-based sealant on the market that is manufacturer-approved for road tubeless. For mountain bike applications, you must use it with a tubeless-ready or UST tire; it is not recommended for those who wish to use a non-tubeless tire set up in a tubeless fashion. It also does evaporate slowly over time, telling us that their unique mixture splits the difference somewhat between a latex and glycol sealant.

Both Bontrager sealant products require a removable valve core and can be injected straight from their narrow-tip bottles; or you can use a measuring injector (i.e. Stan’s) for more precise application.

Continental Revo
Continental is the new-kid-on-the-block when it comes to sealant. Many Xterra racers have used its mountain bike tires with other sealants on the market for many years. This year, Conti launched its own sealant, called Revo. Unlike most other latex-based sealants, Revo uses a synthetic latex base, rather than natural latex. Continental claims that this makes the mixture more stable, but notes that it cannot be mixed with any of the other latex sealants currently on the market because gelling would occur. Note that Caffelatex features a synthetic latex base, so the same rule applies—similar to your car, keep the synthetics together and the naturals together.

As well, the Revo sealant follows the new trend of being completely ammonia free, so it is safe for your tires long-term. The sealant also boasts four different sized particles suspended in the mix, to help deal with more types of punctures: thorns, pinch flats, glass, and the like.

Homemade Mixes
While all of these pre-made mixes are great, there are a growing number of folks who make their own “home brew” sealants. All it takes is a few inexpensive ingredients and your time, but you can end up with a huge amount of sealant for minimal investment.

The majority of the latex-based sealants out there have a similar basic formula:

• Natural latex (often containing a small amount of ammonia to prevent coagulation during storage)
• Antifreeze (Propylene glycol or Ethylene glycol)
• Water
• Proprietary chunks

Essentially what you have is latex paint plus water (for volume) and antifreeze (as a low-evaporation carrier fluid). When these sealant products dry out, it’s the water and antifreeze agent that evaporate, and you get the latex film left behind. This is why you must add more sealant over time, and why you should always keep air in the tires/tubes. Let them go completely flat for several months, and you’ll likely have an inner tube that is glued together with dried latex on the inside.

Search the internet and you can find a huge variety of different mixes; it seems everyone has what they consider to be the best brew. Most start with latex mold builder from a craft or hardware store. Next is the antifreeze from your auto parts store. Propylene Glycol, or PG, is generally more expensive and environmentally friendlier, but many eschew it due to its tendency to have more additives (for auto use) that can botch your brew. Ethylene Glycol (EG) is cheaper, not enviro-friendly, but often has fewer additives and tends to mix better. Water is the easy part. Chunks are the fun part. People are known to use anything from mica to glitter to black pepper. What you’re looking for is something to clot up around a puncture and give the latex time to seal and dry. And the best part is this: even if your puncture doesn’t seal, you’re left with a pretty bike. Who wouldn’t want pink sparkles all over his carbon frame while waiting for the SAG wagon?

To use a home brew, you will want a measuring injector, such as Stan’s or Effetto Mariposa’s products. What appears to be the biggest hurdle with these mixes is simply the handling: Measuring, mixing, storage, and not making your wife livid at your basement science experiment. Is it worth your time? That’s up to you, but some swear by this cost-effective method.

What’s the take-home?
…You must be asking yourself. The sealant waters are muddy indeed. The good news is you have a ton of options. The bad news is… you have a ton of options. The biggest piece of take-home advice I can give you is this: Something is better than nothing. In most every situation any sealant is better than no sealant. You can’t be sure it’ll seal, but why not take a shot? In my mind, sealant is one area of immense potential for future growth. The benefit from the fastest frame, wheels, helmet, and clothing can quickly go to waste if you’re on the side of the road fixing a flat at mile-fifty. As well, I generally recommend using sealant as a preventive measure, rather than taking the chance of the emergency-style systems (especially if you forego carrying a spare tube).

Now, which type of sealant? And what amount? The answer to the former depends on your wheel/tire choice.

For tubeless clinchers, whether road or mountain, you should use one of the true tubeless sealants (latex-based) such as Stan’s, CaffeLatex, Slime Pro, Hutchinson, or Geax TNT. However, if you’re allergic to latex, your only choice that fills this void is Bontrager Super Juice. For tubulars and traditional tubed-clinchers, the jury is still out. Some have had success with the tubeless-intended latex sealants. Others prefer the true tube-type glycol sealants such as Flat Attack, Specialized Airlock, or traditional Slime.

I personally feel that the nod goes to the tube-specific sealants, especially if you store your wheels during the winter and don’t want to deal with continually adding air and sealant to keep the inner tube from becoming latex-glued-shut. The amount varies by manufacturer, but it generally appears that you want roughly two ounces (59ml) for a 700c road tire. As for inner tube type, every manufacturer stated that their sealants work with either butyl or latex.

You may also be asking: Does use of sealant affect my tire choices? Can I get away with a thinner, faster rolling, more puncture-prone tire if I use some sealant? Some will disagree, but I argue that tire choice ought to be independent of the sealant discussion. Sealant is not a guaranteed fix, and won’t turn your paper-thin race tire in to a Conti Gatorskin. A thinner tire will be more prone to cuts… and in 99% of cases, no sealant on the market will fix a large cut on a road tire. For tire choice, let the tradeoff between low rolling resistance and puncture resistance be your tire guide… and if you ask me: Use a sealant either way.