Asking for a friend, i understand it lacks some information but here goes. None the less any help would be appreciated.
Do you need more carbs than the day before when doing back to back rides ?
I.e if you did 3 160tss rides same time same distance, would you need more carbs on the 3rd day compared to the 1st?
In short, no.
But if you have a rest day before the 3 days starts, he has probably eaten more carbs in relation to his daily output that day, making him more ready for day 1.
And if he doesn’t exponentially increase his carb intake during day 1 and 2, he will have a rough time on day 3.
Probably not, although if you are doing multiple high TSS days in a row some protein/carb recovery drink would help. However, your diet should be able to refill your glycogen stores in the muscles overnight provided you eat what you need for the rides you are doing.