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Looking at the two combos, you are trying to keep a similar rolling diameter so as not to alter the gearing? But the tread width is lower, so LESS grip and less precise handling (sidewall slop)?
We don't know important details - what sort of suspension, what rule set you have to comply with and what does it say about this. What is your tyre of choice, and how much freedom does that give you?
First question is, can you run wider tyres on those 14s, maybe go down to /50s too and wear the gearing change?
Can you buy lighter rims - I have ~140rwkw running 15x8s that are about 6kg, 225/45 semis and I would not be within cooee of 16kg.
Tyre choice/rim size can get too big and the drag from the big sticky tyres can make the car slower on the straights (if you run on longish straights), what is your output?
Too summarise, you are looking at a binary solution to a complex problem. Wheel diameter, rim width, power, rubber availability are the main variables, they all presume you have the lightest wheel you can afford.
If you have a tyre supplier that knows their stuff, they can offer good advice. What do the leading cars in your class run (or maybe the fast competitors in same cars as you), that is a good starting point if no other available.
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