The discrepancy you're experiencing between Zwift's FTP test results and your actual rides may be due to a few factors. First, it's important to remember that FTP tests are just estimates, and individual results can vary based on factors like motivation, fatigue, and environmental conditions. If you're consistently exceeding the estimated FTP by 10-15 watts on Zwift, but not seeing the same results in real-world rides, it's worth considering whether the test is accurately reflecting your true capabilities.
Another possible explanation is that the intensity and endurance you're experiencing on Zwift are not translating to the road. Virtual riding and real-world cycling can feel very different, and what feels challenging on Zwift might not be as difficult in real life. Conversely, you might be able to push harder on Zwift due to the controlled environment and lack of external factors like wind, traffic, and road conditions.
That being said, it's still important to use Zwift's FTP test as a benchmark for training and progress. If the test results are consistently higher than your real-world performance, it might be worth adjusting your training zones and workouts to reflect the higher power output. However, it's also important to listen to your body and adjust your training based on how you feel, rather than relying solely on numbers.
Ultimately, the key is to find a balance between the virtual and real world, and to use both as tools to improve your overall cycling fitness. Don't be afraid to push yourself on Zwift, but also don't neglect the importance of real-world riding and training. By combining the two, you can build a well-rounded fitness base and become a stronger, more confident cyclist.