Interesting. I haven't noticed the capability to track in greater detail than the whole bicycle. I see now that you can drill in on the web page https://www.strava.com/settings/gear to add components to a bike. Not quite as flexible as SportTracks (it looks more cumbersome to swap wheels, for instance, on the fly) but it looks like it would cover most to nearly all purposes.

Is it possible to add/edit components from the iOS app as well? I don't see a way to get to component or bike configuration on the iPhone. I see only being able to select existing bikes.