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?

  • I add sealant when it stops holding air. You loose 5 psi in just a couple days add a cap. – paparazzo Aug 24 '15 at 17:54
  • You 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 Stevens Aug 24 '15 at 19:00

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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  • 3
    I'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. – Deleted User Aug 24 '15 at 18:31
  • I think this should rather be dependent on km than on time. – ruedi Apr 4 at 16:56

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