Normally tubes do not give a pressure spec, just a size. Tires always give a max pressure figure. Exceptionally, I bought a universal innertube for a range of sizes: 26—27.5″ (only because it was quite cheap). The box for the tube has a chart listing all the sizes and widths it can support, and a pressure for each size. for 26×1.75″, it gives a pressure of 3—3.5 bar. My tire gives a pressure of 4.5 bar. The chart on the innertube box indicates 4.5 bar only for the largest smallest size (26×1.50). As the air volume increases, the pressure is lower.

e.g.

|--------+-----------+---------|
| 40-559 | 26×1.50   | 3.5—4.5 |
| 47-559 | 26×1.75   | 3—3.5   | ←
| 50-559 | 26×1.90   | 3—3.5   |
|      … | …         | …       |
| 57-584 | 27.5×2.25 | 2.5—3   |
|--------+-----------+---------|

So this is annoyingly confusing. I pumped to 3.5 bar because I’m afraid to exceed the limit spec’d for the tube. Is that the right move?