Will the Shimano Claris FD-2403 triple front mech (max 50t) work with 52t or should I drop the size of my chainset either by complete replacement or changing the chainrings?
The problem with currently available road triple mechs is not so much the size of the outer chainring as the difference between it and the middle ring. The Claris front mech is designed to work with a 50-39-30 combination. The inner plate is contoured to match the 39t middle ring when the mech is correctly positioned over the 50t outer. If you use it with a 52-42 combo, the surface shaping for the 39t middle ring will be in the wrong place. The mech should still shift, but will do so with much less ease and precision than on the correct chainring combo.
Furthermore, its maximum capacity is 20t, so on a 52t outer the cage will not be best placed for your 30t inner ring either. The good news is that examples of the FD-2203 do turn up on eBay from time to time if you are prepared to wait.
Cycle’s Technical Editor