A sub-20 pd. bike should not be a problem, even with steel, but finding one with all the requirements you desire will just require a little or a lot of research. Your local bike shop would probably have a head start in finding one or actually this forum is probably your best bet because there are so many riders with so many different brands of bikes. You might also want to put a post on the frame builders forum because a lot of those guys are really familiar with different brands and their geometry. If you could find the head angle you are wanting, you could just leave the steerer tube a little longer to get the upright position, and if you are not worried about racing or mud I am not sure why you need a 40c tire. I ride a cross bike all winter long with 32-35c tires, mostly rode riding and occassional gravel like you stated. With a 32-35c tire I pump it up to around 75-80psi and roll with it. Clearly it isn't as fast as a road bike with 23c tires but you can ride 17-20mph no problem depending on the terrain. What size rider are you and why are you set on a 40c tire width? Also, what kind of head tube angle are you wanting? I re-read your post and realized you ride some loose terrain, hence the 40c tires. I am sure there are plenty of frames out there with s-bend stays that will accommodate the 40c you are looking for. Someone will post something shortly I imagine.
Last edited by meech151; 04-18-10 at 01:18 PM.