I can get close to 50 mph (safely) downhill on my 30 year old steel framed 8 speed bike with 20mm tubular tires pumped to 120 psi. No problem with riding at 20 mph on the flats and I'm close to 60 years of age. My "aero" CF bikes with deep carbon rims are minimally faster. Speed is irrelevant unless you are racing. Enjoy the ride and stop relying on equipment for minimal performance gains.