Where in their website did you see 18" wheel as optional for LR4?
If you downloaded the PDF Accessaries Brochure for LR4, you get outdated LR3 one. New LR4 accessaries brochure is not yet available for US market. I found this Discovery 4 accessaries brochure made for other countries off google and 18" wheel is not listed as optional. Anyone interested, send me your email address. It's 4.5MB in size, too big to attach here and I forgot which site I downloaded it from. It's was one of those nights where I was all over the internet with 20 web browser windows open.