Originally Posted by Homebrew01

Put the skinniest tires you can find that will fit on your rims. So if your current tires are 26 x 1.75 knobbies, maybe you can find 26 x 1.25 slicks. Just tires & tubes and you're ready to go.

Switching to 700c means new wheels, tires, cassette, chain (if the brakes even reach)

Drop bars mean new brake levers & shifter levers too.

Compatibility is an issue when switching drivetrain components, so you have to plan that ahead of time (7 speed, 8 speed, cassette, freewheel, indexing ....)