Bicycles

Silca bicycle tire sealant uses recycled carbon fiber to plug holes

Silca bicycle tire sealant use...
Silca Ultimate Tubeless Sealant works at ambient temperatures down to 10 ºF (-12 ºC)
Silca Ultimate Tubeless Sealant works at ambient temperatures down to 10 ºF (-12 ºC)
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Silca Ultimate Tubeless Sealant works at ambient temperatures down to 10 ºF (-12 ºC)
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Silca Ultimate Tubeless Sealant works at ambient temperatures down to 10 ºF (-12 ºC)

We've heard about a number of uses for recycled carbon fiber, ranging from water-draining concrete to lightweight surfboards. Now, the stuff has been utilized in what is claimed to be a better-performing sealant for tubeless bicycle tires.

Known as Silca Ultimate Tubeless Sealant, the product is the result of a partnership between cycling tool manufacturer Silca and Connecticut-based Carbon Fiber Recycling.

The latter company grinds up damaged and discarded carbon fiber products – such as bicycle frames, race car parts, bike wheels and aircraft components – after which it separates the actual fibers from the resin matrix, then utilizes a pyrolysis process to strip those fibers of a special coating called "sizing." Although sizing does help the fibers bond to the resin, it has to be removed in order for them to work in the sealant.

That sealant consists of a natural liquid latex carrier, to which the chopped carbon fibers are added. As the bicycle wheel spins, the liquid foams up, suspending and dispersing the fibers within the bubbles. When a puncture occurs, the air pressure inside the tire forces a small amount of the sealant out of the hole. As the sealant shoots out, the fibers in it jam together within the hole, plugging it sort of like a beaver dam in a river. The latex quickly cures upon contact with the air, thus forming an airtight, permanent seal.

While this is the basic fashion in which most sealants work, their hole-plugging particles are typically made of materials such as ground-up rubber, minerals, or even crushed walnut shells. According to Silca, because the fibers in its sealant are unusually long and stiff – ranging from 6 to 12 mm – they're better able to plug larger holes. Tests have reportedly shown that the product can seal holes up to 7.5 mm in width, which the company claims is 25 percent larger than is possible with conventional sealants.

However, because the fibers are so large, the sealant can't be injected into the tire via the narrow valve stem (which it would plug). Instead, it has to initially be poured directly into the tire, while the tire is partially off the rim.

As the liquid latex dries out over time, however, it can be topped up with a fiber-free Replenisher liquid, which is injected through the valve stem. Silca suggests that the Replenisher be added once every three to six months (depending on riding conditions), and that the sealant be removed and replaced once every 12 to 18 months.

Should you be interested, Silca Ultimate Tubeless Sealant is available now via the company website. Pricing starts at US$18 for an 8-oz (237 ml) bottle of the sealant, with the Replenisher going for an additional $12 per 4-oz (125-ml) bottle.

Source: Silca

2 comments
2 comments
DaveWesely
My experience with tire sealant in inner tubes is poor. It works for a while, but eventually turns into a mess. Using the stuff in a tubeless tire makes more sense because they cannot easily be fixed on the roadside.
But having to replace it every year and a half sounds like crazy talk to me.
If the latex dries out with exposure to air inside the tire, why not encase the sealant in a flat tube made of foil or plastic on the inside, and a thin film covered with adhesive on the outside. Stick the adhesive side of the tube to the inside of the tire tread. With the latex protected from the air, it won't dry out. No muss, no fuss.
Taking it to the next level, incorporate the latex layer right into the tire during manufacture.
ljaques
I've seen the Project Farm tests of all the tire sealants and wonder who in the bleep ever runs over half inch diameter (or larger) spikes and expects to drive away safely. Most of my tire tube punctures (when not ridden on the rim, splitting the tube for inches +) have been from small nails and thorns, mere pinholes when viewed in the surface of the tube. I don't see the need to pay top dollar for unknown gains, myself.
@Dave, I believe that the incorporation of latex into a layer could tend to cause a more disastrous delamination. I had a sidewall delam once and it scared the heck out of me when I saw several 3x6x2" thick bubbles on the inside of my tire on the way to my truck in a mall parking lot. It went straight to the tire center from there.