Originally Posted by mr_pedro

Why do people keep explaining how Zwift is not comparable to real life and if you want to learn to be a better climber you should climb in real life???

This is obvious, but it is also not the point. The OP question is how to stop being dropped on the climbs during a Zwift race. That is not asking how to become a better climber in real life. Zwift even has the option to ignore the climb and make the resistance level of the bike feel exactly the same as it would on a flat. If you don’t have a smart trainer, that is even the only option to you.

In Zwift the most important difference between a flat and a climb is that your speed goes down for the same power output and that there is less drag effect. The resistance also goes up if you have a smart trainer, but the standard setting is to simulate only half the grade and there is a setting to adjust this even further down.

OP writes that power before the climb is the same as power during the climb. This tells me that before the climb he is already being stretched above threshold and during the climb as everyone accelerates, he can only just keep pushing above his limit at the same pace as before the climb. But you can only pedal above your threshold for so much time and that is why he then drops off.

This is easily tested. If your FTP is around 200W, what is the average power in the first part of the race before you get dropped off? I bet it is a bit higher than 200W. For example 210W-220W you will only be able to maintain for 10 or 20 min.

So most likely you are not yet strong enough to keep up with the top of Cat C. That is not strange if you just moved up, the categories are quite wide and also people might cheat by adjusting their weight (both up or down), putting a large group of riders right at the top of the categorie W/kg limit.