In the lab with Slime Sealants

The oldest name in flat protection is still getting its hands dirty

When Stan’s tire sealant was introduced in 2001, the tubeless concept was barely two years old and it wasn’t showing signs of thriving. Stan’s latex-based solution eventually changed what was a niche and problematic upgrade into a must-have feature. And like so many great leaps in technology, we went a long time without asking for more. Only recently have viable competitors to Stan’s entered the scene with advantages in longevity, effectiveness and ease of use. Orange Seal took the latex concept and made it last longer, Finish Line abandoned it altogether and meanwhile Stan’s is ever-evolving.

For much of this time, Slime has been conspicuously in the back seat. Before tubeless, Slime was so universal its name had become genericized like Kleenex or Band-Aid. Started in 1989 specifically to serve the mountain bike community, Slime has made inroads into the automotive and motorsports worlds, which now makes up more of its output than does its cycling product.

Slime produces sealant for several brands, but if those brands want the recognition of the trademark Slime color, that comes at a premium, so often you’ll see Slime formula in less slimy shades.

One such automotive product was commissioned by Audi. The auto manufacturer asked for a sealant that would achieve a wider coat on the inside of the tire than Slime’s standard sealant. What resulted was a substance that was more mobile and stayed that way longer. That formula eventually lead to Slime Tubeless, which was released early 2017. The technology in Slime Tubeless, like WebTech, Flow Motion and the Audi-inspired Wide Coverage were developed in its San Luis Obispo laboratory and headquarters, and we recently stopped by for a tour.

I want to know what a milkshake made in a $500 milkshake maker tastes like.

The science of sealant development involves a fair bit of trial and error. Those trials involve making small batches of sealant and putting them to the test. There are plenty of industrial mixers out there, but Slime’s preferred tool is a Hamilton Beach milkshake maker. In the evolution beyond Slime Pro, which was Slime’s early, more traditional-style tubeless sealant, they experimented with removing the natural and synthetic rubber compounds entirely in favor of a focus on mechanical sealant made up of suspended fibrous material not unlike the active ingredient used in its original inner-tube sealant. That yielded a longer life and more predictable performance near the end of it. Further experimenting involved adding some natural rubber back into the mix and changing the makeup of the fibrous material. All of these steps first take place in a steel mug that might have just as easily been destined for two scoops of mint chocolate chip at a Baskin Robbins.

Testing which sealant can best take the heat.

And it wouldn’t be a lab without petri dishes. As formulas are developed, one simple stress test involves putting a small batch in an oven for various amounts of time. Shown here is a tray of Slime Tubeless, still relatively moist after baking for days. In the background are dishes of competitors  put through the same process.

Dynamo Humming

A less simple stress test is this dynamometer. Sealant is installed in a tire, which is spun at high speed for several hours. This mimics the heat, vibration and motion that our sealant faces in the real world. Punctures can be introduced, pressure can be adjusted, and results can be monitored. Just next to this relatively simple contraption is the room-sized automotive dyno where Slime tests its car tire sealant.

For a brand owned by a Fortune 500 company with holdings as broad as Miller Electric welding and Foster refrigerators, Slime has a remarkably intimate vibe. Its product development is driven by riders. And there’s a freedom of experimentation in that development that you’d expect to see from a small independent company, not a huge multinational. Maybe that shouldn’t come as a surprise from a brand on the central coast of California whose business is making a green goop called Slime.