Catrin, I can't really address your question about the brakes, dirt, etc., but I can say that yes, a strong headwind can sap the life out of you, exactly the same as hard climb. The best example I can give you is that the only century I have ever done is almost completely flat, but it is by the ocean. On the way back, you are riding into the wind. The day we did the ride, it was getting ready to storm (it did at mile 85) and the wind was fierce. Although we set our pace at a modest average of 13.5-14.5 and we rarely we riding at a speed above 18, at one point the wind was so tough that we were going around 10 mph in a very low gear. My DH told me that if I didn't get in front and pull for awhile, he would kill me! I have never experienced anything like that again. Since I routinely ride fairly challenging hills, the experience really surprised me.