Tubeless sealant dries out every few months, and refreshing it without an injector means breaking the tire bead, pouring in liquid, and hoping the mess stays contained. Park Tool's TSI-1 Tubeless Sealant Injector skips that process entirely. You remove the valve core, draw sealant into the syringe barrel, insert the injection tube through the valve stem, and push the plunger. Sealant goes directly into the tire without dismounting anything.

The injection tube measures 120mm long with a 3.5mm diameter, which fits through any Schrader valve and most Presta stems with removable valve cores. That length gets the sealant past the valve threading and deposits it inside the tire rather than gunking up the valve channel on the way in. The syringe barrel holds 100cc (3.5 fl oz), which covers most road and gravel tires in a single fill. For mountain bike tires that need more volume, you refill and inject a second time. Fluid ounce and cc markings on the barrel let you measure exact amounts instead of eyeballing it from a bottle.

The TSI-1 works in both directions. You can inject fresh sealant and also extract old sealant by reversing the plunger action, which means you can check sealant condition or empty a tire before a tire swap without peeling the bead off the rim. One note on valve compatibility: some tubeless valve stems have an internal opening narrower than the 3.5mm tube. In those cases, the tube won't pass through, and you would need to break the bead to remove sealant. Injection still works in most of these situations since you can deposit sealant at the valve opening, but full pass-through requires a wide enough bore.... Read More