alo

I am running tubeless sealant in fat bike tubes. I may go completely tubeless in the future.

A couple of times I have had tires losing pressure when the bike is parked. I pumped them up, went for a ride, and they seem to hold their pressure.

What probably happened is, I got small punctures not long before stopping. The punctures were probably above the level of the sealant while stopped, so the sealant didn't reach them. But when riding the bike again, it seems to have sealed the leaks.

Sometimes prickles from plants break off in the tire. I am still waiting to see if something remaining in the tire is a problem with a permanent seal.

Hokiedad4

How much pressure are you losing? One consideration is that at full pressure, a small hole will get larger and lose air, which can seal once the tire loses a bit of pressure.

ClydeClydeson

I used to use Slime brand sealant. It was generally effective, although it also would eventually clog up valve cores. Another thing it struggled to help with was punctures through the tires' sidewalls. I caught the sidewall of my tire on a cactus needle and the tire started going flat. I was able to stop the leak by laying the bike on its side with the damaged sidewall facing down and slowly rotating the tire to cover more area with SLime, and I finished my ride.

I would not be surprised if tubeless sealant works the same - it can't seal what it's not in contact with. I am a bit surprised a partially sealed leak in a fat bike tube can cause noticeable pressure drop - those fat tires are good down to very low pressures, and require a lot of air loss to change the pressure.

Skulking

Tubeless or not, bike tires do lose pressure over time. I'd guess that you never had a hole, just normal pressure loss while the bike was sitting.

alo

I am talking, for example, about stopping for 1 hour and the tire goes too flat to ride. It has happened a couple of times. Another time, it lost pressure over night.

The only explanation I have is that the puncture happened shortly before stopping, and when I stopped, it was higher than the level of the sealant, so it did not seal. But after pumping it up and riding the bike, it does not leak any more.

I am in a place where there are a lot of prickly plants, and I go off road a lot.

Koyote

But not if the Earth stops turning.

bruce19

So, you saved me from making a similar statement.