In the end it’s about %FTP for a certain time. For me, 230 km at 25 km/h is ~50% FTP for 9 hours. If I were to ride at 90% FTP for multiple hours, which I think

In the end it’s about %FTP for a certain time. For me, 230 km at 25 km/h is ~50% FTP for 9 hours. If I were to ride at 90% FTP for multiple hours, which I think is at the border of what's humanly possible, I could do ~33 km/h, so 230 km in ~7 hours. If I were to raise my FTP by 40% to 350 W, leisurely 50% FTP would be ~29 km/h and 90% FTP would be ~36 km/h, so 230 km in ~8 and ~6.5 hours, respectively. What's constant regardless of FTP is the ability to ride for multiple hours without getting saddle sores, joint pain, or running out of energy, which is what endurance is about in my opinion.