Well suburbs aren't exactly so Republican, depending on the part of hthe country. Boston's suburbs are liberal and have been for awhile. new York's suburbs (especially Long Island, & Westchester) have gone from GOP to DEm & now is fairly liberal. Philly's suburbs Montco & Bucks have done the same & are now fairly liberal. D.C's subrubs are moving leftward (Fairfax especially) Denver's suburbs are pretty liberall, Seattle's suburbs are fairly liberal, same with the bay area.
Only midwestern and southern suburbs are "conservative".