Because mountain bikes and road bikes have different uses and designs, the saddles of the two can be seen to be different in shape: the saddles of road bikes are narrower, thinner and longer than those of mountain bikes.

The riding posture of a road bike extends the stroke of the femoris major, quadriceps, and gastrocnemius as much as possible by lowering the upper body, causing the thighs to be more vertical. If the saddle is too wide, it will rub the inner side of the thigh root.

The riding position on a mountain bike is more upright than on a road bike, so being a little wider doesn't particularly hinder leg movement. Also, mountain bikes are less suited to road conditions than road bikes, and a wider saddle will increase comfort.

The riding posture of a road bike determines that the power distributed to the arms is greater than that of a mountain bike, and the road bike is also light-weight, so the saddle is thinner than that of a mountain bike.

As for the reason why the nose of a road bike saddle is longer than that of a mountain bike, it is because the inner leg is raised when riding a turn, and the outer leg is dead on the pedal. In this way, the main force of the bicycle is resisted by the contact between the inner side of the outer leg and the saddle, and the arms can easily and carefully control the details of the steering, making it easier and safer to corner. It can be dangerous if the road bike can't find a place to lean or lean on the wrong position when the road bike is cornering.