When to top up your tires
Every tire leaks. What decides how often you pump is not the tire — it is what you mounted inside it, and the spread is wider than most riders think.
And a narrow tire empties faster than a wide one, which runs against the intuition.
What you mounted decides how often you pump
Every tire leaks. The rubber is permeable, the valve is a moving part, and the bead is a seal made by pressure rather than by glue. The question is never whether yours is losing air — it is how fast, and that is decided mostly by what is inside it.
No nudge yet. You are 2.2 psi down and it waits for 2.3.
| Setup | Per day | From 38 psi, after a week | After two weeks |
|---|---|---|---|
| Tubeless | 0.87% | 35.8 psi | 33.6 psi |
| Butyl tube | 1.39% | 34.5 psi | 31.3 psi |
| TPU tube | 1.91% | 33.2 psi | 29 psi |
| Latex tube | 3.03% | 30.6 psi | 24.7 psi |
A latex tube gives up roughly 3.5× what the same tire loses tubeless. Two weeks in a shed and it has lost 13.3 psi — which is not a slow puncture, it is what latex does.
A narrow tire empties faster
This is the part that catches people. A 25 mm tire loses 1.1% a day where a 61 mm one loses 0.7% — a larger SHARE, not just a larger number, and it runs the opposite way to the intuition that a big tire holds more air and therefore loses more.
| Tire width | Per day |
|---|---|
| 25 mm | 1.1% |
| 32 mm | 0.97% |
| 40 mm | 0.87% |
| 50 mm | 0.77% |
| 61 mm | 0.7% |
The reason is surface against volume. A narrow tire has proportionally more casing wrapped around proportionally less air, so the same leak rate per square centimetre costs it a bigger fraction of what it is holding. A road tire on tubes is the worst case on both counts at once.
When Baró decides to mention it
The app does not nag you daily. It works out what your tire should be at by now and stays quiet until the gap is worth a pump: at least 2 psi AND at least 6% of your target, whichever is larger.
Two thresholds rather than one, because either alone gets it wrong somewhere. A percentage alone nags a 100 psi road tire over a difference no rider can feel; a flat psi alone stays silent while a 20 psi trail tire loses a tenth of itself. The larger of the two is the one that holds at both ends.
A gauge beats a thumb, and neither beats a pump
None of this is a reason to chase a number every morning. It is a reason to know roughly where you are before a ride that matters, and to stop reading a soft tire as a puncture when it is just a fortnight.
If you want to check the model rather than trust it: write down what you pumped to, leave the bike a week, and read it again cold. The table above says what you should find. How the rest of the number is built works the same way — published so you can check it, not so you can take our word.