@Ayjay @Carbon13 I'm similarly interested in the reason for putting Hankooks on in the summer. Some reports the CC's handling is a bit "squishy" in hotter weather? I was planning on having them on all year round.@Carbon13 - Your first para above makes me wonder why you would ever bother going back to the Hanlooks if the Cross Climates are so good. Speaking personally, I found the Hankooks to be irredeemably bad when I had 16" wheels and just couldn't wait to be rid of them!
On your second para, I seem to recall that the reason we all rode 23s at the time was that the science told everybody that the narrower the tyre, the less drag and more aerodynamic it was - until, that it, the science was found to be wrong and we now all know that you can go big (within reason) without losing the other benefits.
Yeah, we were all told narrow and max pressure was fast because it felt fast as we rattled along the road! Had some 20's (possibly 18's) years ago but my aging bones are very glad of the current trend for bigger volume tyres and lower pressures which we are now told is also faster (to a degree, depending on tyre rim interface etc.)