The split seattube has become a "signature feature", of sorts for me.
It's a concept I came up with mainly to accommodate a short chainstay, such as 16.5", on a 29er. It allows me to produce virtually any effective seattube angle while giving clearance for the rear tire. This could, of course, be accomplished with a simple bend or notched and welded joint in the seattube. However, some advantages of the split seattube are:
-Greatly improved pedaling stiffness at the bottom bracket -- From the small handful of split seattube customers I have so far, all have made comment of a notable difference. I also have my own ongoing thrash test.
-Seatpost can be lowered ALL the way if desired. This is a huge plus for those seeking a compact cockpit, allowing infinite saddle heights, all appropriate to how ever you want to ride your bike that day, dropped to the rails if you please, or at full leg extension for an all day climb.
-Water cannot enter the frame via the seattube, one less place.
-The short chainstays that generally accompany this design create a 29" wheeled mountain bike that handles exceptionally well on tight switchbacks and riding conditions where the front wheel must be easy to pull up. The shorter, quicker handling wheelbase is "counter balanced" with big wheels and a slack headtube angle, while the improved lateral stiffness of the bottom bracket shell makes the bike more responsive when you're pedaling your hardest.
This is probably my most performance enhancing option.