Is it just me or is it impossible to extract techs from the AI during wartime? Even if I'm steamrolling them, they refuse to give me even the cheapest techs for peace. I used to love using war in Civ III as a way to catch up in the tech race, but it seems that the developers saw that as an exploit and got rid of it in Civ IV.

I'm running the latest patch of vanilla Civ IV, so you know.

I must say that I have more luck extracting technology than cities from them! I think you really need to push them to the brink of their demise (depends how you define "steamrolling").

I would also imagine that different tribes respond differently to getting "steamrolled" also when it comes to talking peace (apologies - can't point to any XML file on this one, but others may be able to).

The implementation of Vassals in Warlords does address this to some extent, so I guess the developers did eventually bend a bit on this one.

Does anyone know what factors influence how much you can squeeze out of them? E.g. if you've just taken a third city, whether it's better to call them up that turn, or wait to move a big stack up to a fourth city. Whether pillaging/their economy has an effect, or their total number of troops, etc etc.
Sometimes tech is a major factor contributing to war, and it'd be nice to know how best to exploit it.

I assume you mean "extorting" techs...

Best way to loosen up an AI is to take all of their major cities, including their capital, leaving them with just a few fringe cities in the tundra. However, sometimes they just won't do it -- I've had civs willing to give up their 2nd-to-last city for peace, but they STILL won't let go of any technologies! I think it depends on the civilization.