Dear sifus, my car came stock with 225/50R17 tyres and it's about to due soon and I'm actually considering switching to 225/45R17.

May I know any possible impact / changes if I were to do so? As far as I know the speedometer reading may not be as accurate as before and it tends to over-read speed, but is it a lot?

If not mistaken rim size is 7.5 x 17

Thinner side wall.. your actual speed will be lower than the shown speedo reading.

And your ride will be stiffer, or less comfortable, but only slightly since its a 5% reduction (from 50 to 45) in tire side wall.

Too small. Percentage difference is 3.4% smaller in overall circumference. Max difference is 2.5% ideally. Best to keep the percentage difference as small as possible.

225/45R17 91V is usually for C segment cars.
225/50R17 94V or 215/55R17 94V is usually for D segment cars.

Just stick to OEM size. The engineeers that designed the car know whats suitable for the car. Too small might affect safety such as traction/stability control systems. 225/50R17 is pretty common anyways. Lots of choices.

Way too small in diameter, your ride will be noticeably harsher, ride height drops by 1cm and fender gaps increase by the same which makes it look ugly. The closest alternative is 245/45/17 but it's too wide for your 7.5j rims. Another option which you can use is 215/55/17 which is about 0.5cm taller so your ride height also increases by the same. Your comfort will be improved but consequently handling will be more slushy. So this is the only option available for you. I'd suggest you just stick to original size.

Thanks for the advise! Guess I'll stick to original size.