Which alternative is generally preferred?
It is safer and better for the environment to have a slightly higher pressure in your tyres.
“If you fill the tyre 10–15 per cent more than the recommended tyre pressure, it reduces rolling resistance without jeopardizing traffic safety. [...] If, on the other hand, you only have 70 per cent tyre pressure, the tyres are worn twice as quickly. Too low a tyre pressure also deteriorates traffic safety.” (Swedish Transport Administration)
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