All tires have recommended pressure listed on the sidewall, hence calculations for optimal values should start from there and (usually)should not go out of those ranges. Technically this is also true for some rims albeit it's harder to find data. For example one 23mm road tire could be 5-7BAR and other 9-11BAR. If calculator claims that 8BAR is optimal then you are not running tire to manufacturer specs. Of course this doesn't mean that bad things will automatically happen, just increases bad outcome chances.