Ignoring the comfort/performance side, I’d be more worried the rf tyres will crack those lovely 326 wheels. It’s not “if” but “when” unfortunatelyBusterboo wrote: ↑Sat Aug 04, 2018 1:21 amIt's not a matter of harshness, but of performance.
Search the forum and you'll find a large number of posts on the topic. Many say the same thing: you'll never know how good the Z4 is until you dump the runflats.
Rob