Originally Posted by
BikeWNC
Switch the wheels on the two bikes and see then how they feel. The 25c tires on the Roubaix absorb way more road vibration than the zertz do. I ride my Roubaix with 23c tires and put 25c on the Tarmac to smooth it out a bit.
Agree, but...
Switching to the Conti 4000S yesterday, after the first 100 yd., ride-wise I couldn't recall the difference between it and the 25mm Conti 4000. 97 mi. later on a 2010 Roubaix Comp, same thing. On the other hand the 23's definitely feel a little more precise on a 40+ mph descent with a string of 30+ mph curves.
No comment on the zertz, as I don't see any practical way to discriminate its effect on a consumer level.