First I thought it is the bars. That's where I talk with the bike and where we connect. My hands rest lightly on the bars, I look and we go the way I glance.

At a hill I start to shift down, there is no down my bike says "dig deep, we can do this".

The bars are where we are one. But then maybe that is the frame, If not for the frame and the builder's design and my LBS art at bike fit that connection would be lost or feel strained.

So maybe it's the wheels. Each time I've upgraded wheels, or got a new bike with "better" wheels, or even test ridden a bike with different wheels it's felt like a conversation with a new person. A person who is twitchy yet responsive and fast, or stable, predictable and reliable.