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Automobile Engineering

Strut Design, Front Suspension

Introduction:

For many years, rear-wheel-drive cars were equipped with front and rear shock absorbers. Most front-wheel-drive cars are equipped with front struts, and some of these cars also have rear struts. Since massive numbers of front-wheel-drive cars have been introduced in the 1980s and 1990s, front and rear struts are now very common. Struts are similar to shock absorbers, but struts are usually positioned between the knuckle and the chassis to provide knuckle support.

 

Front strut assembly: 

 

  • A strut-type front suspension is used on most front-wheel-drive cars and some rear-wheel drive cars.
  • Internal strut design is very similar to shock absorber design, and struts perform the same functions as shock absorbers.
  • Some struts have a replaceable cartridge. In many strut-type suspension systems, the coil spring is mounted on the strut.
  • The coil spring is largely responsible for proper curb riding height. A weak or broken coil spring reduces curb riding height and provides harsh riding.
  • The lower end of the front suspension strut is bolted to the steering knuckle.
  • An upper strut mount is attached to the strut, and this mount is bolted into the chassis strut tower.
  • A lower spring seat is part of the strut assembly, and a lower insulator is positioned between the coil spring and the spring seat on the strut.
  • Another spring insulator is located between the coil spring and the upper strut mount. The two insulators prevent metal-to-metal contact between the spring and the strut, or mount.

 

Upper strut mount

 

  • These insulators reduce the transmission of noise and harshness from the suspension to the chassis. A rubber spring bumper is positioned around the strut piston rod.
  • When a front wheel strikes a large road irregularity and the strut is fully compressed, the jounce bumper provides a cushioning action between the top of the strut and the upper support.
  • The jounce bumper stops the upward wheel and suspension movement before the spring is completely compressed. If the spring becomes completely compressed and the coils strike each other, ride quality is very harsh.
  • Therefore, the jounce bumper in the strut improves ride quality. Most jounce bumpers are made from butyl rubber.
  • Some late model vehicles have microcellular urethane (MCU) jounce bumpers, which are lighter than rubber and provide more progressive cushioning to improve ride quality.
  • MCU jounce bumpers are also 20 to 40 percent lighter than rubber jounce bumpers, which reduce road noise transmission to the passenger compartment.
  • In relation to temperature changes, MCU jounce bumpers remain more stable and provide improved ride quality regardless of the temperature.
  • The upper strut mount contains a bearing, upper spring seat, and jounce bumper