Not a lot if room for the wheel on the front seat when it has a suitcase on it.
That's a fact.Here's a thought about vehicle packaging. Years ago I had a 1966 MG Midget. It had a full size spare wheel that just about fitted in the boot. No dramas if you got a puncture, other than having to empty the boot to get to the spare. Now I know it was only a 13" rim with a 155 or 165 section tyre, unlike the rims on a Z3, but then the whole car was only about two thirds the size of a Z3. I really don't think BMW took the concept of a practical spare seriously when they penned the Z3....
The wheels which I brought came with Bridgstone RFT's. Replaced with a 'budget' rear set, name escapes me, but cost £300 the pair 255/35/18'sA ford SMax (7seatwr MPV) Hans nonspare at all and not exactly small.
It didn’t have RFT as standard either but I’ve found some Bridgestone RFT that are made for retrofit and put those (it already has TPMS) just in case.
They are 16 inch so have plenty of sidewall but you can tell they are stiffer but as it is fairly compliant already no big deal.
Is this what you have gone for on the Z @Andy McDonnell ?
Not at all unusual, lost count of the number of times when I was working as a tyre fitter doing outside work that I'd come across people who didn't knowI once had a caravan that I used for around 5 years for holidays in Devon, I kept it up here and would take it down twice a year, when I came to sell it the buyer asked where the spare was omg it never occurred to me that there wasn't one, there was a space for it behind the gas bottle that the buyer pointed out to me. how daft is that, not even giving it a thought