There are a ton of tubeless sealants on the market, but most have one thing in common – leave them in your tire long enough, and they’ll dry up. When they do, you’ll be left with dried clumps or sticky patches of cured latex inside your tire. The new Finish Line Tubeless Tire Sealant promises to change that, along with delivering a new method of plugging leaks.

New Finish Line Tubeless Tire Sealant will never dry out

To be fair, there’s more than one company that played a part in the new sealant. Finish Line says that they partnered up with MULTI SEAL who are known for their tire sealants – just in industrial or military applications. Developing a sealant for a bicycle is quite different, so we’re told that this is an all new formula that the two co-developed.

Where the Finish Line Sealant differs is that it does not rely on liquid latex or ammonia. Finish Line claims that this makes the sealant non-toxic, hypoallergenic, safe for carbon fiber, and it even cleans up easily with water.

New Finish Line Tubeless Tire Sealant will never dry out

Without liquid latex, the sealant has to rely on another mechanism for sealing punctures which is where the Kevlar comes in. Called FiberLink technology, the sealant is filled with small pieces of DuPont Kevlar fibers which are forced into holes when there is a leak. When enough of those fibers are forced into the hole, they mesh up and create a plug. Since the liquid carrier isn’t tasked to be the sealant as well, Finish Line was able to use a liquid that won’t dry up over the life of the tire.

New Finish Line Tubeless Tire Sealant will never dry out

New Finish Line Tubeless Tire Sealant will never dry out New Finish Line Tubeless Tire Sealant will never dry out

After some puncture testing of our own, the sealant works surprisingly well, plugging holes up to 1/4″ and cuts up to 1cm in the tread area, and it almost sealed a 1cm cut in the sidewall. As noted in the video, small amounts of air were still escaping from the plugged holes, but that could be due to the fact that we didn’t ride the tire after it was punctured. Finish Line states that as you ride, the FiberLink mesh will continue to tighten and reinforce the plug. That seems to match up with how the sealant plugged the larger holes above. Once it was sealed at lower pressure, adding more pressure would open up the hole a little more, and additional fibers would rush in and seal it again. You could keep going like that until the tire was holding pressure at 32psi. It’s pretty fascinating to see the strands of Kevlar sticking out of the holes after the sealant has plugged the leak.

When it comes to first impressions, the Finish Line sealant seems fairly impressive. If it lives up to the “it will never dry out, never need refreshing, and lasts the life of the tire” claims, then this is indeed a revolutionary tire sealant. Seeing as how we just got samples in last week, we’ll have to check back in with a long term review.

Finish Line recommends 2-3oz for road tires, 3-4oz for gravel, 3-4oz for 26/27.5″ tires, 4-5oz for 29″, and 6-8oz for fat bike tires. There’s no need to shake it, it’s safe to use with CO2 inflators, and it will work down to -10°f. Available soon, Finish Line will offer the sealant in 4oz, 8oz, 1 liter, and 1 gallon containers with prices TBA though expect it to be on par with current pricing of other tire sealants. For the shop setting, the big containers can be used with their industrial-grade pump which produces 1oz of sealant for each pump.

*Finish Line’s claim of a lifetime sealant has changed a bit since the product was launched. Under ideal conditions with a non-porous tire, the sealant performs as expected. But with more porous tires, the water portion of the sealant evaporates causing the sealant to thicken. Because of that, the company is no longer marketing the sealant as lifetime as of 09/2018.

For more details, check out our interview with Finish Line here.


  1. If it works as advertised this could be real game changer. The number one reason for me not to switch to tubeless is because I don’t get flats that often, having to mess with sealant for every wheels on every bicycle in my shed every few months is much more work than dealing with a punctured tube once in a while. Without the whole sealant maintenance thing tubeless just got a whole lot more interesting!

  2. Video unavailable for me also but super interested in the idea. Even though I usually find my sealant is still OK when I check the cleaning out is a pig and I still worry about it so tend to add a bit more which is slowly putting the weight up. Does this need a similar quantity as other sealants (therefore weight)?

    • I used it on my TCX SX cross bike, it didn’t go well for me at all. I lost 4oz in less than 20 miles of riding from a cut that was 1/8 of an inch across. I think the 50psi was too much for it. It did seal at 40psi

  3. If it works as advertised, this could be the holy grail of tubeless sealants. Worst thing about latex sealant is not know how solidified it has become in side the tire without peeling off the tire.

    • Agreed, and even if there is a meaningful amount of liquid sealant, the particulate has usually bonded itself to the tire’s casing, preventing it from traveling to the leak and doing its part in sealing the hole.

      I’m interested in seeing a comparison. It sounds as though this initial impression/test showed that at 32psi, it was able to seal, but will it hold up to higher pressures in gravel and road situations (the latter being a big challenge for all sealants, in my experience)?

      I also find it appealing that it’s easy to clean out. I’ve patched cuts in TL tires before to save them from premature landfill duty and cleaning the sealant off the inside of the casing to apply a patch is a big part of the chore.

      • Note that in the test video, we were just stabbing holes and seeing if it seals. Finish Line says that as you ride the bond will get stronger, which should mean better sealing if we had ridden the tire after it went “flat”. That’s something we aim to test out next.

  4. This kind of reminds me of the microbeads that they used to put in lotions. Someone correct me if I’m wrong, but it seems like this would introduce microscopic Kevlar fibers into the water supply and put animals and humans in danger of ingesting them. It’s the same issue as with plastic particulates in the ocean. I say this as a huge fan of Finish Line’s other products.

  5. It seems as though this would introduce microscopic Kevlar fibers into the food chain via water sources like those beads that were banned from use in lotions. Is this sealant ecologically safe?

    • That is a great question – perhaps THE question to ask of any new product… Is this product going to end up like ‘micro bead’ face washes, polar fleece etc and flood the oceans with nasty stuff?

      • It will never make a huge impact. Not that many people ride bikes with sealant. Huge numbers of people use body washes with micro beads.

    • Considering how much of a niche product sealant is and numerous competitors I very much doubt that even if there’s any effect it’ll be too marginal to even research about. You might as well start bothering about CF dust washed down the sink after the steerer was cut.

    • Kevlar doesn’t break down readily in normal conditions, but it’s also not toxic to plants or animals. As far as environmental concerns go this is probably pretty low on the list of things worth worrying about, and it’s definitely not in the same league as the micro-beads in face wash, strictly from a scale standpoint. If you think about the amount of this being used x the number of cyclists compared to the amount of people buying facewash, it’s pretty insignificant. Especially if you consider that facewash is designed to be washed down the drain and into the water supply, while this will have very tiny amount leak out under normal use.

    • Microbeads make it direct to the ocean because they go down your drain and into the waste facilities to get pumped out. Anything solid that drains into your yard or landfill will stay in the soil until it begins decomposing…however long that is.

    • What is really bad is dust created when cutting/recycling/prepping fiber reinforced plastic. I don’t think fiber segment are small enough to be a real treat. Sure don’t eat it but that does not look particularly dangerous.

    • Any environmental damage is bad, its just a little is how we managed to make no progress since all the warnings in the 80’s. There has to be something bio degradable they can use. Bamboo or hemp fibers perhaps. I suspect this will fall foul of certain laws.

      Were all for the hemp right?!

      That said if it doesnt dry out and does indeed strengthen its a godsend for the riders.

  6. I’m interested in hearing more about this and the Boyd bubble gum sealant. Maybe Bikerumor could do a sealant challenge now that there are several worthy options out there.

  7. there was a sealant in the late 90s trying to compete with Slime called Tire Lightning (i think). it was Kevlar based,sounds a lot like this.
    my concern is that without a drying element, there will always be some leakage. it may get you out of the woods, but you wont be able to ride in ignorant bliss like you can with a latex sealed puncture.

    • Agreed, it seems like without something that dries and sticks to the surrounding casing, there won’t be a membrane formed, and it seems tough to imagine this fiber plug won’t shift around and seep a little each time the casing is flexed. That said, this isn’t just some outside company that doesn’t understand the demands placed on a bike. Finish Line has been in the bike biz for a long time, so I’m willing to give it a try.

    • I had the same thought. No latex, with a lot of fiber. Slime never seemed to get much traction with tubeless users until they came out with their own latex product several years back, but maybe these guys have a new spin on it that nails (no semi pun intended) what slime couldn’t.

  8. Seems like a lot of manufacturers have already been down this path, and reversed back up it later – Bontrager Super Juice was exactly this idea too – non latex (glycol based i think), with fibres in to ‘coagulate’ around the puncture spot – but they don’t do it now, and the current Bontrager TLR sealant looks to just be another latex based sealant albeit without ammonia.

    I used the Super Juice all the itme, and thought it was good – be interesting to know why Bontrager/Trek backed away from it…

    • Hey David, I notice that the title of the article says “New Finish Line Tubeless Tire Sealant will never dry out” Is this only over the “life” of one tire? (“it will never dry out, never need refreshing, and lasts the life of the tire” ) Or does it really never dry out to the point where the leftovers can be reused in a fresh tire. Additionally have you used it on a hard wearing tire like the Schwalbe Marathon Almotion. In an average commuter application in the city I live in we’d expect a tire like this to last between 1-5 years, if this means commuters can run without tubes or punctures for 1 whole year that would be a game changer for many people. Will you be researching and/or promoting this product outside of the “performance” side of the industry?

  9. Recommended amounts seem 1-2oz higher than recommended by Stan’s, etc. Any particular reason for that? 5oz is a lot sloshing around a 29er wheel.

    • @Jim E – my guess is that the carrier is inert so all the clogging is from the particles. So effectively you “dilute” the active ingredients (i.e. kevlar strands). There’s only so much you can do when you have to fluidize it.

      Whether this is better in practice or not than a congealing sealant I have no idea. But it looks neat. And for something like a tubular CX application maybe ideal (unlike my fatbike, I never ride it at 0 F or below).

  10. Curious about it not clogging valves like many of the competing brands. And the qtys stated for each tire size seem like 1 oz more than the current products which equals more rotating mass…please correct me if I’m wrong on this. Overall if all claims hold true it seems like a cool product

  11. I’m wondering about old sealant contaminant, can you add it to a wheel that already had/has a latex sealant inside or if you would need to dismount the tire and scrub all the inside surfaces of the rim and tire and clean first.

  12. Installed new DH tires and thought I would give this a try. 4 days later and tires still go flat after about 8 hrs an leave puddles of slimy clear liquid on floor. It will not even seal a new tire bead to a rim (Stan’s and Orange Seal will do that in a few minutes) so I doubt it would ever seal a puncture . Will be washing it out tonight and going back to Stan’s.

  13. PLEASE DON’T BUY THIS PRODUCT! This stuff does NOT WORK! As soon as I installed it, the sealant wouldn’t plug a very small hole in my tire. I rotated it and shook it many times, then waited 24 hours to ride but it immediately started blowing out sealant when I tried riding. I was very hopeful this stuff would be valuable, but it’s been the opposite by not even lasting to the first real ride. I also had help from a local shop because I thought I might be doing something wrong, but it turns out the sealant just wouldn’t seal the tire. It says the sealant will fix holes up to 1/4”, but the hole I have is significantly smaller and still won’t seal. The fact that it doesn’t dry out never allows the stuff to cure and truly fix the tire.


    • Exact same “luck” – I do not recommend buying this sealant. I had 80ml of it not seal a puncture after many many many attempts. I loved that it cleaned up easy — because it got everywhere.

  14. Just had my first puncture with finish line and I will be washing it out. It could not seal a 2 mm hole. Rubbish. Cursed it every time I had to pump my tyre up as it went flat again as I staggered home.

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