any disadvantages to 19" wheels?

[Perfectlap]

well you have to consider the weight of a 19" wheel which is more of factor than the size. The factory 18" turbo twists are 30 pounds. That's about as heavy as I would go. The factor 18" Carreras are 20 pounds, as are many forged ($$$) wheels which have the advantage of being pot-hole proof and light. With a big heavy cast alloy 19" you get the worst of both worlds. And not only are the tires pricier there are also fewer choices. If you ask me most 19" wheels make the Boxster look a little goofy. You'd have to lower the car (never mind that the Boxster is very well set up right out of the box without lowering) and lowering has its own issues on rough urban roads, things come loose, start to rattle, break, etc. As far as performance you're probably better off with a 17" light wheel with more sticky rubber to fill that wheel well.