GT Force Carbon Pro

The suspension on the GT uses a four-bar linkage in conjunction with a medium to high pivot and idler. The idea of this system is to enable the rear wheel to move in a rearward direction for a significant part of its travel. The idler wheel is there to separate suspension forces from the drivetrain. As you can imagine, as the distance grows between the rear axle and the BB the chain will come under tension. However, by installing an idler, which itself has a near-fixed distance to both the BB and rear axle, you can manage to negate the problem.

The adjustable chainstay length will of course change the travel and kinematics slightly. That said, I think it’s a great option to have and it’s great to see brands like GT offering real and useful adjustments. I would imagine that it’s not a purely selfless act, and making just the single sized rear triangle helped keep costs down.