When it comes to vehicle seats, the best ones are those that you seldom think about. They’re so supportive and comfortable that you don’t realize how long you’ve been sitting in them. They provide good position for visibility, and if they fold, they’re easy to operate.
What isn’t easy is making such a seat, and automakers spend a great deal of time and effort designing them.
“It’s difficult to make a comfortable seat,” says Eva Greiner, project leader development compact class for Mercedes-Benz in Germany.
“You need to have the cushions not too soft so you sit like on a sofa, but soft enough that it doesn’t hurt or push in a certain area, and gives you lateral guidance so you don’t move in curves. It’s supposed to be pretty, and have additional functionality so you can adjust the seat.”
Each vehicle has different dimensions, which affect the seats.
“I have to fit the seat to the car, not the car to the seat,” Greiner says. To this end, the team writes a specification book — known as lastenheft to the German team — which outlines the parameters of the project, including how the company will market the car and what it will cost. The process takes nine months.
Several factors must be considered, including the height of the floor and roof, the position of the airbags, how easy it is to get in and out, and the angle of the leg between the hip and heel when sitting. The type of car defines the position as well.
“When you get into a sports car you want a feeling that you’re crawling in, but with a family car you want to get in quickly,” Greiner says.
Different body sizes must also be taken into account, and Mercedes-Benz uses a formula that accounts for between five and 95 per cent of most people.
“We don’t meet the smallest and the largest when we design a car,” Greiner says. “It doesn’t necessarily mean they cannot sit in the car, but it’s not in our data. It’s a wide range. Some manufacturers only do 10 to 90 per cent.”
Once the engineers have defined the seat’s width, height and dimensions, it goes to the styling department for upholstery, but it isn’t finished yet. It will go back and forth between the departments numerous times until everyone is satisfied.
“It takes a lot of people to sit in the seat,” Greiner says. “You can make an 80 per cent guess, but you always need to have feedback from real people."