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So, I switched to tubeless only a few months ago, making this the first winter with tubeless. I've been a little surprised at my results. In some cases, I can remove a little thorn and expect to see it sealed quickly. Other times, a very small, pinprick hole leaks and leaks until there is a nice puddle of sealant on the ground. I converted initially using Orange original but now top off with Orange Endurance, as I got a great deal on a large bottle of it. My topping off is done through the valve stem. I use these bottles with these large dispensing needles to add through the valve stem-- no need to break the seal.

So, my questions:

  1. I understand that Endurance does not have quite the sealing power of original, being designed to require less-frequent refills rather than optimizing sealing ability. A part of this is the little grits 'n bits that are added to stop up holes and give the sealant a point to adhere to. What have you tried that is effective at this? I've heard quite a variety of ideas-- fine sand, fine- and course-ground pepper, glitter, even the hairs shaved from one person's face. What actually works for you?
  2. How much of my recent failure-to-seal could be attributed to cold or to tire pressure? Due to drastic temperature changes and time since inflating, my tire pressure was probably about 18PSI, down from my normal 32PSI. It was about 36°F. I removed a very small thorn, leaving a tiny hole that leaked without sealing at all. This went on for several minutes. In the end, I added more sealant and pumped up the tire to 32PSI. This quickly resolved the problem. However, the tire had a full dose of sealant already, and more was being actively expelled when the hole was facing down, so it doesn't seem to be a question of quantity of sealant. Was it the cold, the (counterintuitive) lack of pressure, or absence of the gritty stuff? I know you can't definitively answer based on the information here; I'm just looking for the thoughts and experience of those that have been riding tubeless longer than I.
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  • From what I understand, the effectiveness of a sealant also depends the speed it flows through a hole (the faster the better). Bigger holes are sealed faster, as the sealant flows faster through them.
    – Rеnаud
    Dec 21, 2021 at 17:37
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    18 psi isn’t /that/ low for a lot of mountain bike applications. Durable casings and 2.6” make it a pretty good pressure for a lot of folks
    – Paul H
    Dec 21, 2021 at 21:29
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    @Criggie While some people do ride that low, I usually ride at 32PSI. I'm on the bigger side for MTB. I was going to deal with the leak and then the pressure, but it turned out that the pressure fixed the leak.
    – Andrew
    Dec 21, 2021 at 23:37
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    @Criggie I run 22psi in 2.6" tires. The bead retention features on modern tubeless rims are pretty strong. Even 18psi still results in hundreds of pounds of force pressing the bead into the rim wall. The stiff casings Paul describe also really help.
    – MaplePanda
    Dec 22, 2021 at 4:02
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    @MaplePanda fair enough - my main point was more that 18 PSI is ~half the given "normal" pressure, which feels insufficient, rather than the raw pressure measurement.
    – Criggie
    Dec 22, 2021 at 4:55

1 Answer 1

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Some general commentary:

  1. I now prefer to install sealant by dumping it in (not through the valve). I find that the particulates inside can sometimes settle out of solution because the valve injection method is slower.

    Your choice of installation method is especially poor in this regard. You have a 3.3mm needle through which all of the sealant and particulate must flow. Consider that sealant is generally able to SEAL punctures twice this size — not the best idea to install it like that in my opinion.

  2. Sealant usually has particulates added already. It's uncertain whether adding more helps or hurts. Please refrain from using glitter for environmental reasons (also leaves a huge mess if you DO try it — don't ask how I know). I'm also concerned about pepper and any possibility of an unwanted chemical reaction.

  3. Consider why the Endurance bottle was so heavily discounted in light of supply vs. demand.

  4. Cold temperatures definitely play a role in sealant effectiveness. Since it is a chemical reaction, the reaction rate coefficient is affected by temperature; lower temperature = lower reaction rate. I believe the rule of thumb is that reactions halve in speed for every 10°C/K decrease in temperature?

    I think this point doubly goes against your choice of Endurance formula sealant. Not only is the Endurance stuff watered down intentionally, but now its rate of reaction is even further reduced.

  5. Regarding tire pressure, I do believe it has an effect. Perhaps the higher velocity of the ejected sealant makes it polymerize more rapidly? You can use your finger to rapidly uncover and cover the puncture, which can sometimes help it seal.

I must make a product recommendation here: Stans' Race Sealant is arguably the most aggressive sealant out there. It's worth a try I think. The freezing point might be an issue though depending on how cold your winters get.

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