So, I have been doing the W4SB program for over a month now with the main goals of gaining muscular size and strength. On the repetition upper body days I have been doing the standing dumbbell French press exercise -with one dumbbell in each hand- for primarily the triceps and the standing alternating dumbbell bicep curl as my elbow flexor exercise.
The thing is is that it seems that I can only French press with 15 lbs. in each hand for about 10 reps at the most (without going to failure) while I can do standing alternating bicep curls with 20lbs. in each hand. for about 10 reps on each arm (without going to failure). I know that the triceps are supposed to be stronger than the biceps. So I am wondering if I actually have muscular imbalances in my upper arms?
You are weak, but you do not have an imbalance. If you really need reassurance, french presses (overhead tricep extensions?) put you at a big mechanical disadvantage compared to normal tricep extensions. I can only do 75 for sets of 13-ish with overhead tricep extensions, and I can strict curl 95 for moderate reps, and curl 95 for high reps with normal form. My triceps are also a lot stronger than my biceps. I also easily use 100 for sets of 12+ in normal tricep extensions, and can even do 105 for a good amount of reps for tricep rollback extensions (since my elbows take less of a beating).
Really, do not over think this. Train both, and if you really want to make sure your triceps get an advantage then train them before biceps.