Here’s a little known fact: few bike upgrades—if any—comes close to the value of great tires. That ultralight aero wheelset your fellow cyclists have been raving about? Will perhaps improve 2-3% of total performance. That overpriced, oversized ceramic derailleur pulley? Good luck ekeing more than 1% of performance gain out of it. A pair of supple performance rubbers, on the other hand, is a potential game-changing gem; it can easily gain as much as 5% of performance increase compared to stiff, touring model—equal to the performance gain of dropping 7 kg off the bike. Supple tires, especially the wider ones, also improve comfort in a way carbon handlebar and/or seatpost can never match.
Tires, therefore, should occupy the top of bike upgrade/improvement list.