It might not look like much, but this little cup of goop and its creator, Stan Koziatek, are responsible for how today's mountain bike wheels and tires are made. Starting with his sealant, Stan built an empire; he came as close to reinventing the wheel as anyone in modern mountain bike times, and in the process, seized the tubeless throne from the 100-year-old company that invented it.
If history went the way everyone expected it would, this story would be about the first Mavic Crossmax UST wheel. Since that's where it began, it would only be logical to credit Mavic for the modern tubeless system. But the French company merely planted the tubeless seed–Stan's sealant was the fertilizer.
Tubeless brought the promise of running lower tire pressures without the danger of pinch flatting, which, in mountain biking, is the Holy Grail. But UST fell short of that promise when Mavic released it to the world in 1999. Even though the tires were built with a butyl layer and a specially designed airtight bead, they still let air escape over the course of a few days.
This wasn't good enough for Stan, so he formulated a latex-based liquid to coat the inside of the tire and seal the microscopic holes left in the not-so-airtight UST rubber. It worked, and soon he noticed that the liquid was filling thorn punctures as well, so he added differently sized and shaped platelet-like particles that would automatically clot gashes up to a quarter-inch in length.
Since the sealant was doing what the heavy butyl layer of the UST tire failed to do, and would automatically seal punctures as you were riding, it could essentially antiquate the UST tire before it could ever take hold. Stan began selling the sealant and a rudimentary tubeless conversion kit consisting of packing tape, electrical tape and a valve he'd liberated from an inner tube with a punch.
Naturally, people began sealing conventional tires with Stan's. Mechanics referred to this as "ghetto tubeless," implying that they didn't think it'd be around very long. Seriously, who would've thought that taping valve holes and using a messy liquid would beat out the millions of dollars in research and development Mavic had invested in UST? Stan did. "I knew from the beginning that the sealant-based system was going to take over. We used to stop several times during mountain bike rides to fix flats. It's just what we were used to. The sealant made the rides a lot harder because we never had an excuse to stop and rest anymore. Riding without tubes and normal tires converted with sealant is much faster. That's when I knew it would be perfect for racers."
And it was. World Cup cross-country racers Thomas Frischknecht and Christoph Sauser were early adopters of 'ghetto tubeless,' and they were winning races with it. Soon, Stan was supporting nearly every team on the World Cup circuit.
But it was still pretty ghetto. Non-tubeless tires lacked the correct bead needed for a secure interface with the rim. It only became legit when Stan finally convinced Kenda to make a Stan's-branded hybrid tire that used a normal casing in order to ditch the now-useless butyl layer, but retained the tubeless bead. Tubeless-ready was born, putting the final nail in the UST coffin. These days, nearly all wheels and tires made for mountain bikes are tubeless-ready. And it all began with a cup of latex.