Is there a formula for adjusting a driver’s seat to an ideal position? Car sharer
Driver seats and steering wheels are increasingly adjustable to meet the physical dimensions of most people, and other controls are also positioned accordingly. But human variations are so numerous and sometimes so extreme there is no mathematically precise anthropometric formula for every single individual.
Not only are your height, your weight, your limb proportions, and your natural body movements unique, but so too are your posture, your habits, and your preferences.
You have to find your own “best-possible” driving position within the available adjustables, and in accordance with some essential principles: Clear Vision. Precise Control. Alert Comfort.
Here are some pointers on how to fine-tune your own seat settings to achieve that:
Your weight should be supported in five places. Your back (moderate) your hands (light) your bum (heavy) your thighs (light/moderate) and your feet (light/moderate).
Adjusting the back rest: Your lower back (lumbar region) should be in firm contact with the back of the seat. Your shoulder blades should touch the back of the seat, but not press against it. Your head should not touch anything! For drivers, the term head-rest is a misnomer – it is a head restraint to help prevent whiplash injury in the event of an accident, not a pillow! If the back of the main seat is too sloped you will forfeit the “alert” requirement and reduce vision; if it is too upright you will upset overall balances of reach and weight, restrict your arm movement, and not have enough gap between your head and the top restraint pad.
From the correct seated position, straight outstretched arms should be able to reach the top of the steering wheel without leaning forwards. This means that with your hands on the East-West sides of the steering wheel, your arms will be slightly bent at the elbow (relaxed) but still stretched forward enough that your upper arms are not obstructed by your chest when you steer, and you do not have to twist your torso for sharp manoeuvres.
Adjusting the seat squab: Your bum should be in the wallow towards the back of the seat squab (the springing and cushioning is designed for about half of your total body weight to be there) with your thighs resting gently on the cushioned surface in front of that. If your thighs do not touch the cushion, they are not sharing weight, so your sit-upon muscles (gluteus maximus) will be more put-upon during long journeys.
You should be able to fully depress the clutch pedal with the ball of your left foot without fully stretching your left leg. If you have to straighten your leg completely, your left thigh will have to press down too firmly against the seat springs and cushion (undue effort).
Your right foot does not have to move so far forward to operate the accelerator and brake. The right thigh should rest lightly on the cushion. The right foot should be able to operate the accelerator with the toe while the heel remains on the floorboards.
Your ankle is doing the work. When it moves to the brake it should be able to press the pedal with the ball of the foot while the heel is off the floor. Your thigh is doing the work.
Once you have met all those parameters with the seat back, and then with the squab, there is scope for fine tuning to get the best “balance” between the back and squab adjustments (one directly affects the other).
More and more cars now have a “height” and “firmness” adjustment for the seat squab. This is a matter of preference but can also help if you struggle to find a good balance between back and squab.
