Ibis launched its versatile Tranny hardtail at the first indoor day of the Interbike show Wednesday. The new frame is made entirely from carbon fibre, but has an intriguing wrinkle that makes it "three or four bikes in one" according to Ibis' Hans Heim: completely separable seat- and chainstays.
The objective is to make one frame that can be used as either a geared bike or a singlespeed. To that end, Ibis needed a way of adjusting the chainstay length that was lighter than an eccentric bottom bracket. The answer: a plug-in chainstay held in place with aluminium and titanium bolts, with enough overlap and friction surfaces that it would lock into a rigid structure when joined.
The plug-in design provides half an inch of adjustment, equivalent to an eccentric, and Ibis expects the weight to be in the 1200-1300g range.
The joint areas are made from compression moulded carbon fibre, as are the rear dropouts, though the latter are hidden by a protective steel skin. A choice of geared and non-geared dropouts will be included with the frame, so you can choose to build it up your way.
The frame being separable also adds a third use to the Tranny: as a travel bike. Ibis' suspension bike, the Mojo is easily dismantled for travel and the frame then fits into a box the size of the wheels, which means US airlines don't whack you with a US$150 bike tax.
A fourth use might also be as a bike that can be converted to a 29in wheeler by simply replacing the rear subframe; that's not something Ibis is promising, but it's a distinct possibility.
The Tranny you see here was literally the first one out of the mould and some aspects of the new frame are yet to be thoroughly tested, Heim says. When BikeRadar asked, Heim says he doesn't yet know for sure how well the joint will tolerate repeated dismantling and assembly, thought "preliminary testing looks good."
With some details still to work out, Ibis expects to ship the Tranny in Spring 2008. The frame will cost US$1399, with a complete Deore XT equipped bike at $3599.