I need speed. I have a 13-30 in back and a 24-45-50 in front. Can I replace the 50 with a 52? (Trek 1420)
I would recommend replacing your rear cluster to 11t or 12t -28
24-45-50 seems a bit odd to me. the tooth spread on the front is getting extreme, if you are correct.
5t from middle to big ring and 21t from small to middle? is that how the bike came? to be safe and in range you should bump up the small ring along with the big ring if that is the way you want to go.
and change the rear cluster and new chain would give you the most effect.
There are two kinds of people in the world, "Those who help themselves to people, and those who help people!"
Also: You should watch your cadence: I ride around 100 rpm (usually). It is much better for your knees.