235/40 on 18x7.5 is an illegal fitment : for MOST but NOT all 235/40R18 tyres.
+55 isn't a legal offset either.
Your _legal_ offset range is from +40 to +52.5
Double check that +55 offset for OEM rims - I am confident that is _wrong_ and the correct value is +52.5
If you want to use 8" wide you can (possibly contrary to ROH advice), but the offset should be as high as possible - preferable +48 to +52. +45 should be OK, but it would be borderline, and with any of the 8" wide fitments you should consider you will need to roll rear gaurds. The lower the offset, the more trouble the fitment will be in terms of rubbing and what you might have to do to resolve that.
RX-8 whee;s are 18x8+50 and that's a decent fitment, but does run close to guards with 235/40 wrapped around them.
Can't comment on the hankook, but 225/45R18 on 18x7.5 is a good fitment....+48 is what I consider the ideal offset for this fit...because it placed the tyres inside track within 0.5mm of the stock position.
"Blue Meanie" 2007 Aurora Blue MPS 3 - 18x8.5+44 SSR GTX01 - 235/40R18 Michelin PS5 - 3.5" ETS TMIC - CPE stg 2 mount - HKS/CPE BPV - 2XS inlet - 2XS short shift - Corksport turbo manifold - HT 98 octane tune - Leather/Aluminium handbrake - Momo shifty knob - 7" touchscreen - JDM Mazda Retractable dashtop screen assembly - Bespoke Raspberry Pi Android based GPS/Carplay and instrumentation - 36AH reserve battery and C-TEK isolator - TEIN Street Advanced coilovers 1" drop - Superpro bushings - 220Kw/410Nm.
"Lipstick" 2013 Velocity Red MPS 3 - 18x7.5+48 Enkei RPF1 -225/40R18 Federal RS-RR - CPE TMIC - COBB inlet - CPE stg 2 mount - COBB Stage 1 98 octane tune - COBB shifty knob - 2XS short shift - 2XS turbo manifold.