Originally Posted by
jimmuller
Thank you. This makes perfect sense. From this answer I reason the difference between older days vs. now: With steel frames the tire's ability to absorb shock was less important because a lighter frame was more compliant anyway. With CF frames (and wheels) the frames can be very stiff while still very light, to the point where they are too stiff to ride easily or efficiently over long distances. So wider tires are used to compensate.
That is incorrect.
25s, carbon tubulars will make a steel bike perform better as well due to the contact patch shape (rolling resistance) and lighter weight over alloy rims.
Note that these are tied to wider rims to maximize aerodynamics and contact patch of wider tires.
Carbon rims are going to 23-25mm wide.
Most old wheels are in the 18-19mm width range.
Ride characteristics of carbon frames depends on the frame design. The advantage is compliance with bottom bracket stiffness and light weight that steel cannot match.
Wider tires are not making up for carbon frames.
This is simply a realization that wider tires are adding benefits without old school beliefs about narrow being a panacea for max speed problems.