DT Swiss rims - what are they thinking???

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So I've just spent 45 minutes trying to mount a GP 4000s tire on a new DT Swiss RR 465 rim. I've been using the GP 4000s for years on OP rims, and have never had a problem mounting a tire in a couple of minutes. I decided to give the DTs a try after hearing from numerous sources that they are higher quality, more precise rims. Now, 45 minutes later, the first tire I've tried to mount still isn't fully on...and at this rate it could be another 45 minutes of wrestling. My thumbs are cracking.

I've tried everything I know about how to stretch a tire over a rim, with no success. There has to be a trick, or DT would've been out of business years ago...right? Anyone want to share the DT club secret with me?

What on earth do people do when they're out on a road and get a flat with these wheels...or is that just not an option?