Tires, indeed. I had 23's on my '85 Trek 460 and threw some Bontrager 25's on for 2 seasons. Then went back to Michelin Krylion 23's. Wow, the front end got light on me, acceleration was quick once again.

Last August I acquired the Trek 760 that had very heavy Conti 25's that I swapped for Avocet 23's (22 actual) and that difference was similarly dramatic as the the 460. Both bikes are dedicated race platforms and easy to tell tire differences.