I've got a set of tubeless tires that have been on my mountain bike for over two summers and have had zero flats. How often should I be adding more sealant? How much? Should I be removing old sealant first?
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I add sealant when it stops holding air. You loose 5 psi in just a couple days add a cap.– paparazzoCommented Aug 24, 2015 at 17:54
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1You don't want to wait until the tire stops holding air as you want to make sure you have enough active sealant to plug any small leaks/penetrations that occur while you are riding.– Glenn StevensCommented Aug 24, 2015 at 19:00
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2 Answers
At minimum, you should replace the sealant every 6 months or so. As you have found, a good tubeless setup will stay inflated well beyond that time, as the latex in the sealant has already sealed any small holes. However, the sealant does dry over time, so the systems ability to self-repair when you run over a thorn or sharp rock is greatly reduced.
There is no need to clean and remove the old sealant. However, some brands tend to leave clumps that you can pick out.
If you're valve cores are removable, the easiest way to add sealant is through the valve. Otherwise, you'll have to break the tire bead off the rim (just a small section) to add sealant. This can sometimes take a few tries to get sealed again (helpful to have a compressor or large CO2 cartridge to "slam" the tire into the rim).
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3I'll add to this that if you have a "seansonal" rig, it's sufficient to change it at the beginning of the season. I do my summer bikes at the beginning of the summer and my snow bike once the first flurries hit. Commented Aug 24, 2015 at 18:31
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3@ruedi Most sealants specify that they 'last up to 6 months in the tyre', so time is more important than kms– NZDCommented Jan 25, 2021 at 22:06
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It can actually be quite dificult to get the sealant through the valve as it tries to seal the holes including the syringe opening and the valve itself. It just clogs my syringe instantly. Commented Jun 2, 2022 at 7:04
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@ruedi The sealant dries out as a function of absolute time elapsed, not distance ridden. Of course your puncture risk increases the farther you ride, but it's fairly obvious you'll need to refill your tires if you have sealant spraying out everywhere. Commented Jun 3, 2022 at 0:43
And probably consider temperatures. In the summer, it’ll frequently be in the 100’s here. I’ve found that it dries up much more quickly when it’s hot.
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1The temperature is a definite factor to consider. Nice addition to this question.– Ted HohlCommented Jun 2, 2022 at 4:13