Black Ox Sealant is a new bike tire sealant designed to work for mountain, road and gravel bikes (even in inner tubes for basically any bike). Its secret sauce is a mix of different length carbon fibers blended into the latex-based sealant.

And those fibers are chopped in house to control the lengths, then blended with other materials to create a sealant that uses both physical and chemical properties to plug holes up to 9mm in diameter. To test it, they shot the spinning tire with a rifle:

They also tested it with three different screwdrivers puncturing the tire, ripped out at once, with surprisingly little air pressure lost:

black ox sealants carbon fibers plugging a puncture hole in a mountain bike tire

Carbon fibers help fill a puncture hole to clog it up, helping the sealant coagulate to plug the leak.

It’s made in Oxford, North Carolina, using technologies and materials borrowed from their parent company, which makes products for the aerospace industry. It’s good down to 20ºF (-6ºC), with a cold-weather formula planned for later this year. They say it’s compatible with other brand sealants and Cush Core inserts.

Retail is $5.99 for a 4oz bottle, $17.99 for 16oz, and $28.99 for 32oz. They recommend about 2oz for a 700×40 gravel tire, moving all the way up to about 10oz for a 29×3.8″ tire. So, probably best to get the bigger bottles.


    • John on

      Is this really a serious queston? The worst thing you contribute to the environment is the carbon fiber hairs that may or may not escape the tire in the event of a puncture? Exactly how many punctures a month do you expect to have?

    • retro_slouch on

      It never will. Carbon fibers are essentially just carbon graphite, and will not decompose. Carbon composite bike frames and components are particularly tricky since they contain strong resins and adhesives that make it trickier and more expensive to recycle. 99% of sealants are already non-biodegradable and are not very nice for plants and animals to consume, thanks to oils, rubbers, and other nasty stuff. This is a latex-based sealant, and so we’re getting a few real nasty bits together into a not very friendly cocktail.

      The bike industry has never focused on sustainable practices, and there is no good option for a nice air-holding solution as far as I know. The closest match would be the biodegradable Effeto Mariposo sealant that was posted here recently, but this is likely very resource-intensive to make, as it uses olive pits. (They are likely able to get pits from food processing factories though, which reduces impact.)

    • Jeff on

      the increase in CO2 production from your elevated breathing rate during said exercise that caused the puncture is probably far worse for the environment. So you should be sure to hold your breath during the entirety of your ride.

  1. TIm on

    Why do so many companies think “testing” their product with a firearm is somehow impressive? If I’m in the market for a bulletproof vest, yes I want to see the demo where the test dummy is unharmed after getting shot close range, with a high caliber armor piercing round. If I’m in the market for tire sealant, I’m much more impressed with a rock stabbed into the sidewall at low speed that doesn’t cause a total flat.

    • Jon Hinman on

      Yep, go back to driving a car, and replacing/disposing of wearable parts that each have more of a carbon footprint than a whole bicycle.

  2. Artie on

    I am simply amazed how haters can down play such an awesome ground breaking product. Carbon is in everything including us. Using a rifle to demonstrate how effective this product is genius. Nothing can be more destructive to a pressurized tire than a bullet hitting the side wall. Hi how would pass through likely causing it to expand. Leaving a larger exit hole. These people are obviously jealous but I am amazed. So my question is how soon will it be available for cars and trucks and how can I become a part of the sales and distribution? Because this is huge. Congratulations on this product. Eagerly wanting to help bring it to the masses.

  3. Seraph on

    I like that the video showing it seal on a spinning tire has a major cut in the edit, basically not showing the actual point in time where it seals the tire. So basically we have a video that claims to show the sealant filling a .22 hole but never actually shows us just that.

  4. Gone Bike'n on

    Wow, there is some weird organized negative “enviromental” campaign against this product. The couple of ounces contained within a tire will have zero impact. Carbon by it’s nature is inert. These posts are totally bogus. I haven’t used this product, but it looks promising.

  5. Morgan on

    Just wait till you have to run your hands through the inside of the tire when you have to throw a tube in. You’re going to get carbon slivers like crazy doing that.

    • TheKaiser on

      Aside from the other environmentally based objections, this is actually a really good point you bring up. Anyone who has worked in hand’s on carbon manufacture or repair for an extended has experienced this issue. I’d wondered about the internal risks of of breathing in fibers spraying from a punctured tire, but hadn’t thought about external risks to the skin.

    • Randal Bladel on

      Naked carbon fiber, without a a hard epoxy resin, are quite soft. You will not get a carbon fiber sliver from them. I think they are softer than fiberglass fibers I have worked with, Nor will you be subjected to “sprayed” carbon fiber, as it will be coated with the latex solution.

  6. Nick on

    They test it like that because it’s fun. Have a sense of fun. Besides, we finally have sealant that is perfect for hunting season on those days we forgot to wear orange.

  7. briannystrom on

    I have nothing against the product per se, but their recommendations for how much to use are insane! Ten ounces in a 29×3.8 tire? I wouldn’t use that much in a car tire, let alone ANY bike tire.


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