hello,john!
front-rim: 1,85/18 alu
rear rim :2,15/18 alu
the first silver-star, as shown at the ifma in cologne was fitted with this original "grünert" mz-aluminum-rims.
you can also use both rims in 2,15.
think of the different front-wheel-hub spoke-length.
dimension is similar to etz 251/301 with grimeca disk
all parts you need are available by:
http://www.zweirad-schubert.dewith best regards from bonn/germany
uwe walter