Does Tubeless Sealant Expire? How to Know When to Top Up

Tubeless sealant is brilliant — right up until the day it quietly dries out and you discover it the hard way, mid-ride, with a puncture that won't seal. So does sealant expire? In the bottle, barely. Inside the tyre, yes — and knowing the timeline saves you a walk home.

Why sealant dries out inside a tyre

Latex-based sealants work by drying to form a plug when they hit air. That's exactly what you want at a puncture — but it also means the liquid slowly cures over time as tiny amounts of air pass through the tyre. Heat speeds it up: a bike stored in a hot garage or ridden in summer will need topping up sooner than one kept cool.

The signs your sealant is spent

• No slosh. Spin the wheel and hold it still — if you can't hear liquid moving, there's little left.
• Dried skins or a "milk-skin" ball. Peel the tyre and you find rubbery films instead of liquid.
• Small punctures that used to self-seal now leak. The clearest sign it's time.

How long does Magic Milk last?

Magic Milk Tubeless-Pro Hi-Fibre is built to stay liquid and ready for around 6+ months (nearer 3+ months in very hot climates) before a top-up. Because it's a synthetic-latex formula, it seals cleanly without curing into heavy clumps inside the tyre — and there's no natural latex, so no harm to rainforests either.

How to check and top up

1. Deflate, unseat one section of bead, and look — or remove the valve core and dip a spoke to check the liquid level.
2. Top up to your usual dose (see our ml-per-tyre guide).
3. Re-seat, inflate, spin, and you're good for another season.

The easy habit: refresh at the change of season and you'll never think about it on the trail. Stock up from the tubeless range.