Two Wheel Blogs

I have done some experimenting over the years with tubeless conversions, and various tire sealants. My findings are by no means Earth-shattering, or even interesting probably. I just thought that I would share some thoughts on sealants that I have learned through my trials. I certainly welcome any comments or disagreements. I have tried to present the facts, but I am pretty much a failure when it comes to unbiased reporting. It is obvious what I think works...if you choose to go tubeless.

That said, here are some thoughts on tire sealants:

Let’s talk tubeless Sealants

Sealants exist in several forms. I will limit this discussion to the liquids that are commonly used. This means that I will exclude (except for the following sentences) the aerosol cans available that not only inject sealant, but also inflate your tires. These aerosol cans often contain propane (flammable) as a propellant, and many times the sealant chemicals in these cans are also flammable. If that is not enough, some contain caustic chemicals that cause oxidation and pitting of aluminum (and other metals), and they can result in breakdown of the tire (that can lead to explosive failure). Suffice to say, I do not recommend aerosol cans with sealant in them…commonly marketed as Fix-a-Flat or similar products.

I will discuss two basic groups of liquid sealants that are available. These are latex-based, and everything else. But before I do that, I want to mention a couple things that I believe are mandatory for MTB sealants: The liquid has got to flow (needs to be watery) in order to distribute quickly. Additionally, it needs to seal the hole completely and quickly. The reason for this is simple...if any air is escaping, it will not be long before the tire is totally flat and provides no service. In larger tires (such as those on a lawn mower) this is less of a problem because the volume of the tires is so much larger (it may take hours for the tire to go from fine to flat with a slow leak...compared to minutes with a MTB tire).

I am not a fan of thick sludgy sealants because they tend to distribute slowly and often times do not stop leaks before the tire becomes too soft to ride. Another strike against thick sealants is the difficulty associated with getting the sealant to slosh up into the bead and seal it against the rim (or rim strip). I have found that with thicker sealants, if burping occurs, a slow leak will result at the burp site and the tire will go flat shortly after. Thinner sealants (especially those with a lot of latex) tend to suffer this problem less (they reseal more effectively).

What is burping? Burping is when the tire suffers an event leading to the bead becoming momentarily unseated, usually some air is lost in the moment before the bead re-seats. I find that thick sealants that contain a lot of fibers tend to be the worst in a burp situation (the fibers become lodged between the bead and the rim and actually prevent resealing).

EVERYTHING ELSE

The “everything else” category is a huge category that contains sealants like Slime and MANY others. To use some sweeping generalizations, I will say that these sealants use chemicals of various sorts to slow or halt the leakage of air out of a tire. Many also incorporate fibers to assist in the plugging of larger holes. In my experience, none of these products stop leaks very well, but rather slow them down to a more manageable rate. Some contain caustic chemicals that can do some real damage to tires and wheels. Simply put, I have not tried everything, but what I have tried has led me to the conclusion that latex based sealants work best for MTB tires.

LATEX-BASED

The Latex Based category is also a large category really. As in the “everything else” category, there can be a lot of different stuff in these sealants to help them do their job. Since, I am not a testing engineer for tire manufacturers, I have a hard time giving the end-all be-all answers here, but I will try to arm you with enough information to make a decision.

Let’s look at the 2 most common Latex-based sealants available; home brew, and prepackaged.

HOME BREW Latex Based

Home brew recipes exist all over the Internet and elsewhere. Here is one:
1. Tablespoon of latex.
2. ¼ cup of water.
3. Tablespoon of windshield washer fluid.
4. Tablespoon of Slime.

This recipe already throws a wrench in my classification system by using an “everything else” type sealant (Slime) into the Latex brew. The reason it does, is for the fibers that are present in Slime. These fibers give the brew a thickness that aids in plugging larger holes.

I have seen similar recipes that include Glitter, Ammonia, and even Automotive Antifreeze. The glitter is an agent that is supposed to help with the larger holes, while the Ammonia, Antifreeze, and Washer Fluid, are supposed to reduce the freezing point, but what else might they do?

When you look at these recipes, one thing that becomes apparent is the vast range of chemicals that we are introducing into the critical link between us and the earth (our tires). I am not sure what these chemicals will do to those paper-thin tire casings. Ammonia is sort of harsh, and I can envision it reducing the sidewall strength. Antifreeze is not always pure ethylene-glycol; sometimes it contains petroleum compounds which are not good friends to rubber. Washer fluid? That stuff is so variable you have a hard time even finding an accurate list of contents on the container…and just what brand are we talking about using anyway (Prestone has 3 types of washer fluid available, all contain different chemicals to do different things)?

PREPACKAGED Latex Based

First off, I don’t have any affiliation with any manufacturer of this stuff, but I am pretty familiar with some of the products out there. Some have done testing and have communicated with tire manufacturers to determine what is OK and not OK to use in the brew.

One thing I really like about Prepackaged sealants (in general) is the consistency of it…Not the viscosity, but rather how constant the ingredient concentration tends to be (Brand X now will be quite similar to Brand X next time you need some more). This helps reduce unwanted interactions (chemical reactions) from taking place in your tires (due to incompatibility of introduced chemicals) when you introduce a new dose of the stuff.

I am not trying to convince anyone to buy any particular product…In fact, I think the guy that makes home brew and really understands the chemicals (and their potential reactions) he/she is using, can probably develop a superior sealant to anything out there…but if you have the knowledge to do that, why are you reading this?

The most common latex based tire sealant in the realm of bikes is probably Stan’s (NoTubes.com). As I understand things, Stan’s is a brew of chemicals that is relatively stable in a tire, but becomes unstable when it leaks out to the atmosphere (resulting in sealing the hole). This instability can (and will) result in premature hardening of the sealant. There are some known triggers that can cause this premature hardening to occur. Some people (including NoTubes.com) claim that CO2 inflators do it...I am not in a position to argue that, but I have seen it happen in the absence of CO2 also (in automotive and MX tires, and my bike tires). I suspect that either rapid pressure or temperature changes will cause this slow reaction to speed up (yes, I said “slow” because the stuff is hardening/drying up from the day you put it in). A CO2 inflator will cause both a rapid temperature and pressure change...perhaps that is the mechanism?

While Stan’s does not seem to list the contents of their sealant anywhere, it seems to be a water based, odorless, white liquid with some sand-like solids in it. It would be impossible for me to state the chemical compatibility between this product and the tires I use, but Stan’s has gone on record to say what is compatible and what is not. Of the tires listed that are not compatible, Stan’s says these tires should be avoided due to problems inherent with tires ability to work tubeless and not the sealant interactions with the tire.

I realize that I have only talked about Stan’s Brand as a latex based sealant…I hate to present only one. There are others available, but I have limited experience with them (I have used about 3 varieties marketed to the MX and Commercial equipment crowd, but they were a little too thick to seal a lower volume MTB tire quickly). Of the brands available, I prefer those that are thin and watery as they distribute evenly and quickly. I also would avoid anything that has a foul odor, and has any warnings regarding skin contact (it is going to happen as some point, and when it does you will probably not have soap and water available). I have a feeling that there will be some more competition in the market in the near future for Stan’s because I think it is a growing market.

In summary, no tire sealants are ideal. This is one reason that I do not recommend them for riders not interested in the hassles associated with experimental performance items...it is not plug and play. The best we can hope for is to use what is available to get the most out of life. For some, the choice will be to not use sealants at all (this is the “most-ideal” practice since most conventional MTB tires were designed to use tubes and no sealant), for others, the choice will be experimental concoctions of chemicals that work best for their special needs. Where you fall on the spectrum has everything to do with your needs, and expectations.