Sorry I can't help with the 18" wheel question.

Since posting in the thread about tyres I've now changed (finally) my awful Bridgestones to what consider an all-round better tyre, the Kumho PS71.  I also have these on my MX-5 and anyone who's chosen tyres before for that model will know how fussy the car can be, re handling etc and tyre choice.

Glad to say although the Bridgestone were well past there best re age the Kumho are fantastic in comparison. An understatement to say it's transformed the way the car handles and mostly the noise levels have most notably dropped in comparison to the very noisy Bridgestones.

Edited 15 February, 20224 yr by MickA

Pilotsport 4 (~15k miles), currently have Premium Contacts on the front axle virtually the same feel as the 4's hopefully they wear less.