Skinnier tires=faster speed??
Well, I feel I must report my own experience with thinner tires, just to be on the record...
I am sure that it is probably true for many of you that you gain speed when you put on skinnier tires. But oddly, it did not seem to make a difference for me.
I went from 700c x 38cm tires on my road bike to 700 x 28cm tires (with smoother tread as well). That's quite a difference to jump in tire width.
Although it "felt" a bit quicker and more responsive on turning, etc,...according to my bike computer and my wristwatch my usual 21 mile ride did NOT get any shorter at all, time-wise. I re-checked the time about four different times under varied conditions. Interesting!
Your mileage may vary (ha ha)....