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cyccommute, thanks for that constructive response! : thumb:
To clarify, the rides I refer to were long rides (100+ miles), not touring, so certainly a bit off topic. And they weren't particularly cold, starting in the high twenties, reaching the mid thirties, ending a little below freezing. I had increased my shoe size as you suggest, perhaps not enough. I had adequate insulation on top, obviously not enough below. That was my point.
I don't mean to imply my body heat was getting transmitted to the ground, but rather to the air. Metal transmits heat well, and quickly moving air takes it away.
The heat loss I'm talking about took many hours. I was plenty warm over my whole body, with the exception of thumbs, fingers, and feet. I conclude that my body heat was leaving those areas faster than it was reaching them. And it was leaving them and into the air, both directly and from the bike.
[MENTION=73614]rhm[/MENTION], I think a large part of the problem is simply that our bodies have to send that warm blood down long limbs so the blood that gets to our feet is considerably colder than our core temp before it even starts trying to warm our feet and fingers. (I have spent a lifetime trying to warm feet at the ends of skinny 34" pant legs. My fingers at the ends of 34" shirt sleeves don't do much better.) I suspect those with stockier, heavier limbs do far better (but I have never been able to get those guys to let me try them to see for myself).
Ben