Pedal Steering Interference (PSI) can be a problematic phenomena in the design of moving BB (MBB) recumbents. When riding a MBB recumbent which is prone to PSI by design, the pedalling driver is steering the bike unwantedly. This happens, if the position of the BB is moved forward.
||The greater the distance d and the force of the pedalling driver, the more the bike wants to turn left.
However, the driver is - while pushing into the right pedal - also pushing on the left side against the seat as a raction.
This force wants to turn the bike back to the right side.
||Also, the PSI is dependant of the position of the steering pivot relatively to
the riders hip joints. If the steering axis goes
right through the center between the riders hips then PSI is minimized.
You will find this at all center-steered bikes. This bike has noticeable PSI.