[2011z435is]

I bought a 2011 z4 sdrive35is about 6 months ago and it looks like the OEM run flats in the rear will be needing replaced soon while the ones up front still have plenty of life left.

Now I know ideally all 4 tires should be the same brand/type, but would it be possible to replace the rears w/ non run flats... like the Michelin PSS and wait until the fronts run out of tread to replace those with non run flats as well?

thanks for the input