I thought I’d talk in this installment of Tech FAQ about a few tire sealants that are available, as I get so many questions about them. If you’re not familiar with the installation of a tubeless system, check out the video below.
One sealant install tip: It’s easier to pour sealant into the side of a mountain bike tire while you are mounting it rather than through the valve stem, as you would with a road or cyclocross tire, because the amount you are putting in is greater.
Tire sealants fall into two basic categories (although there is some overlap):
• a suspension of flakes and fine fibers in a liquid, or
• a natural or synthetic liquid rubber (i.e., latex).
They all take advantage of escaping air, the tire’s rotation throwing them to the outside, and gravity to stop air leaks. One type stuffs the hole closed with fibers and particles; the fibers wrap around the chips and form a plug. The other type closes the hole off with solid rubber that solidifies as compressed air passes over the liquid rubber as it escapes through the hole. Some sealants contain ammonia or other chemicals that can damage rims over time.
Most of the fiber/chip sealants contain a mixture of water, a water-miscible carrying agent such as propylene glycol, and the bits and pieces that will fill the hole. These can be paper fibers, synthetic fibers, mica flakes, polyethylene chips, hydrated bentonite clay, and all manner of other items that will clog a hole. A sealant need not have the glycol; it could be completely water-based, but it would tend to separate and freeze at temperatures often encountered while riding and could dry out quickly.
Sealants can be poured into a tubeless tire when mounting it, or they can be injected through the valve of a tube or tubeless tire. Injecting through the valve is best done by first removing the valve core to avoid clogging the valve. Latex-based sealants can be injected through Presta valves with non-removable valve cores, but fiber/flake-based ones cannot (you can remove the end nut with pliers and allow the valve pin to drop down into the tube, but you have to pinch the tire or tube with your fingers to hold the pin below the valve or you’ll lose it during injection or removal of sealant).
Given enough time, most sealants cease to be active and should be cleaned out; if they solidify, they unbalance the tire with useless weight concentrated in a single spot. Removal is easy to do on a tubeless tire by removing the tire; the fiber-based sealants can be wiped out and rinsed out with water, and the latex-based ones can be rinsed or peeled out once solidified. On a tire with an inner tube, including a tubular, you’ll need to remove the sealant through the valve, which requires removing the valve core, and ideally rinsing and sucking it out.
If a sealant is used in a tube tire that subsequently gets a puncture, you must remove the penetrating object or it will flex in the tire, continually un-sealing the hole and shredding the tube.
Stan’s NoTubes: The original liquid latex-based sealant on the bicycle scene that made it possible to run non-tubeless tires as tubeless, Stan’s seals well up to quite large punctures. Stan’s offers a syringe injector as well as rim-sealing tape and rim strips to run non-tubeless rims as tubeless.
Effetto Mariposa’s Caffélatex: A foaming synthetic latex-based liquid sealant containing no ammonia. The foaming action created by the tire’s movement is intended to seal sidewall and rim-side punctures, while most sealants, thrown outward by centrifugal force or pulled down by gravity when stationary, only seal the tread side. Available with rim-sealing tape and syringe injector.
Vittoria/Geax Pit Stop: Two different brands for the same product, this is an aerosol containing a foaming latex-based sealant. Via its flexible tube, inject it through the Presta valve with the valve core in place to seal/inflate a new tire or to seal a tire that has received a puncture.
Hutchinson Fast’Air: Fast’Air is an aerosol containing a foaming latex-based sealant. Via its flexible tube, inject it through the Presta valve with the valve core in place to seal/inflate a new tire or to seal a tire that has received a puncture.
Schwalbe Doc Blue: A liquid latex-based sealant in a squeeze bottle, you can pour it into the tire on mounting or inject it through the valve with a syringe.
DT Swiss Tubeless Kit: A liquid latex-based sealant in a squeeze bottle, you can pour it into the tire on mounting or inject it through the valve with a syringe. Seems to solidify in the tire in normal use more rapidly than other latex-based sealants.
Slime Pro: Consisting of fibers and chips in a glycol-based solution, Slime was the biggest-selling bike-tire sealant before latex-based sealants came along. Now, Slime Pro combines a latex-based sealant combined with a fiber/chip sealant to plug holes as well as to seal tire beads more like a latex-based sealant.
Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”
Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.
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