McLaren entered the production sports-car world a few years ago with the McLaren MP4-12C. More recently, the British automaker unveiled its second production model, the 650S and 650S Spider, and retired the 12C. Though roughly 75 percent of the 650S is carried over from its predecessor, the changes are significant.

The convertible’s design appears to derive more from the McLaren P1 supercar than the 12C, and underneath its body panels is an improved chassis that provides better handling than the 12C. In tur…