WARNING: LONG POST, I am procrastinating and not writing my paper right now.

Quote Originally Posted by KnottedYet
Dumb question: how do you know you are drafting someone, or vice versa? Like, I had some dude ON MY BUTT for a couple miles once when I was riding the 'bent. Was he drafting off me?

What does it mean? Is it easier? Are they just cutting the wind for you?
Yes, it is definitely easier when you ride less than a bike's length behind someone else. It can be as close as 5-10 cm for maximum effect. Very useful, especially in a head wind. Doesn't make a huge difference on climbs, except perhaps when very windy. If the wind comes from the side there are different techniques (you move a bit to the side, being careful never to have your wheel overlap with the front rider's - if the wheels touch, the person in the back, and many others behind her if there's a whole paceline, goes down! ).

The person in the back is very close to the person in the front which makes it about 20-30% easier to propel herself forward. Over the long run, if two or more people do that together (like exchanging pulls every 5 minutes or 1 km or even 30 seconds depending on your strategy) they save a lot of energy. That's the reason why cyclists race as a team. Think about Lance: he does not do all the work, his teammates actually "pull" him for a fair amount of the time (although Lance specifically was known for taking more than his share of wind-time). When the time to attack comes, he's fresh. Triathletes are often unfamiliar with drafting because they are not allowed to in their races. [Speaking of triathlon: using your aerobars while drafting is a big, big no-no, and will get you rightfully kicked out of a paceline.]

Drafting comes with responsibilities. The person in the back has an easier time, but is at greater risk than the person in the front. One second of inattention can have great consequences, because as I pointed out earlier if wheels touch the person in the back goes down. Major pile-ups happen this way, and other sorts of accidents too. The person in the back's field of vision is also obstructed by... well, the person in the front's butt. So you don't see obstacles/potholes/incoming pedestrians/parked cars as well if you're in the back. So the person in the front HAS to know that there is someone in the back, so she will signal the obstacles, and make appropriate signals to indicate turns, stops, railway tracks, potholes, etc. When she decides to stand on the pedals (or to sit back down), she announces it because it causes the bike to jerk back by about 5 cm, enough to scare the person in the back if she's following closely.

Important: when drafting, you're supposed to look through the person in the front's hips, not directly at her wheel. Looking at her wheel will make you micro-correct your trajectory all the time, and in the end you'll be zigzaging all over the place (also very bad - you want to be predictable). Use your peripheral vision.

So obviously you want to draft behind someone who knows that you are there, and who knows what they are doing, and who are conscious of their responsibility.

I ALWAYS look over my shoulder every other minute, just a quick glance, to make sure I am alone. If I found someone drafting behind me, which happens at high traffic hours with lots of commuters, or when riding at popular roadie spots, I just start making the appropriate signals accordingly. If for some reason I don't feel good about that person drafting me, I will signal that I am slowing down and motion the person to pass me. It is also good manners to alternate at the front if the two riders are of similar strength, and even if they aren't (then the weaker person just takes shorter pulls).

The fine art of drafting and pacelines could take a whole book to discuss, with topics like "how to find a suitable speed" and "practicing the wheel" etc. But I have to go back to my paper. *sigh*

As a final note: Some people do not draft. Ever. They can't stand the idea of sharing responsibility for their safety with other riders. You can totally opt out of drafting if you like. Personally I think it's great to draft with people I know and trust, which includes most members of my bike club, and to teach the others how to do it properly. I find that we can go further together, and I like that. But it's a tradeoff, and I have to be conscious of the risks.