Spare tyre size when running 235/55/18

[JAC13]

Hi... I know this has been touched on before but was hoping for any new advice/updates.
I am currently running Comfessor CF1100 235/55/18 A/Ts. I have not looked yet but I'm assuming the spare is a 16. What size tyre could I still fit underneath that would be the closest match to main wheels.
Van is a 2018 swb t6.

 

[sparkzer]

205/75/16 seems to be the closes size, if it will fit however is a completely different question, its about 30mm over stock - Link

 

[TrevorK]

The standard 205/65r16 is around 6% smaller and should suffice if you are intending to use the spare to ‘get you home’.