There are parts of a bike that you can absolutely feel, and parts that a skilled rider can feel. Easily noticeable: * Tires. Wide supple tires make a huge dif

There are parts of a bike that you can absolutely feel, and parts that a skilled rider can feel. Easily noticeable: * Tires. Wide supple tires make a huge difference, especally as the quality of the road goes down. They're no slower than narrow tires. Narrow high pressure tires chatter, the feel faster from the vibration, but they're not when tested. * Fork. Carbon forks change the vibration profile dramatically, aluminum forks are pretty harsh in my memory, and steel can be liveish, or just harsh and stiff, depending on how it's built. An aluminum or steel bike with a carbon fork rides very similar to a carbon frame carbon fork. Less noticeable: Handlebar/Seat. These cantilever out, and there is flex, but it's subtle. On the other hand, if you don't have a good seat for your anatomy/riding style, it's the single best upgrade you can make. Stem/Seatpost. There's some flex in these, but it's much less than the above, but they still are there. Possibly noticeable: Frame stiffness/Weight/Wheel stiffness I've got three bikes I ride now, a Carbon/Carbon road bike, with 25mm max tires, a cheapish Al/Carbon Fork "all road" bike that's had 700cx25, 700cx35, and 650bx42 (Babyshoe Pass) tires on it, and a handbuilt steel tandem with 26x42mm tires. I've also ridden most combinations of Steel frame/ Al/Carbon/Steel fork, Al Frame w/ Al Fork/Carbon Fork, and Carbon/Carbon. The narrow tires are horrible, except on excellent roads, of which there are a few. The 650b tires are nearly the best thing I've ever put on a bike, with the possible exception of a seat that fits my butt. They glide on bad chipseal, where my riding companions chatter their cables and teeth. They're ok on everything this side of singletrack. The Al/Carbon bike still feels a little dead, and it doesn't really reward high power spinning, which I attribute to the heavy stiff frame and the carbon fork. The Tandem just feels alive riding, and you can see the fork flexing over road noise. It's got a quality of ride that just isn't there with the other bikes. My next bike is going to be Steel with a pretty flexy fork, and probably a pretty noodly steel frame at that. (Looking at a Crust Canti Lightning Bolt or best match, if I can ever get one). It'll have 42mm tires minimum, and maybe 48's if they will fit with fenders. I'm not racing, I'm riding alone or with friends, not super long nor super fast, but 60->100mi at 16-18mph depending on terrain, wind, and fitness levels.