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Chapter 45 Suspension Systems Frames • Body Over Frame – The body and all major parts are bolted to the frame – Design is used on many pickups and SUVs • Unitized Body – Tends to be more tightly structured – Is designed to transmit impact energy throughout the vehicle Springs • • • • Carry vehicle weight Absorb road shock forces Maintain correct ride height The amount the compress under load is called spring rate • Spring compression is called jounce • Spring extension is called rebound Spring Types (cont’d) Shock Absorbers • Dampen spring movement • The faster a shock moves, the more resistance it has to movement • Typically has more resistance to extension than compression • Gas charged shocks are effective at limiting fluid foaming Gas-Filled Shock Shock Absorber Ratio • Valves may provide different resistance for jounce and rebound • A 50/50 shock is equal for jounce and rebound • Damping rates depend on piston and orifice sizes as well as the closing force of the valves Stabilizer Bars • • • • • Also called a sway bar or antisway bar Reduces body roll or lean Typically a one-piece U-shaped steel bar Held to the control arms or strut with links Used on the front and rear suspensions Strut Rods • Found on models that not have a double pivot lower control arm • Greatly affected by braking forces and road shocks Leaf Spring Rear Suspension Coil Spring Rear Suspension Semi-Independent Suspension • Used on many FWD models • Twisting of the axle allows for semiindependent movement • Only remove one shock and spring at a time Independent FWD Rear Suspension Electronically Controlled Suspensions • Adaptive Suspensions – Use electronic shocks or variable air springs – Sensors monitor vehicle height, speed, steering angle, braking force, damping status, and throttle position – Some systems are automatic while others allow drivers to select modes – Reduces body roll but does not eliminate it Types of Electronic Suspensions • Adaptive Systems – Typically use electronic shocks with variable valving • Load-leveling Systems – Use air shocks in the rear to compensate for vehicle load • Fully Active Systems – Use hydraulic actuators as both spring and shock absorber System Components • Compressor • Sensors • Electronic shock absorbers • Electronic struts • Control module • Leveling control Adjustable Pneumatic Suspension MagneRide • Regulates fluid flow by a variable magnetic field produced by a coil in the shock • Shocks filled with a magneto-rheological fluid • Current flow changes the fluid’s viscosity Active Suspensions • Refers to those controlled by double-acting hydraulic cylinders call actuators • Each acts as a variable spring and shock • Hydraulic pressure varies to adapt to changing road conditions • The computer monitors actuator position and load, steering angle, body roll, and lateral acceleration ... Rear -Suspension Systems • Three basic types: – Live axle – Semi-independent – Independent • There are various types within the three basic types Leaf Spring Rear Suspension Coil Spring Rear Suspension. .. Bushing movement produces heat • Worn bushings allow suspension movement MacPherson Strut Suspensions • Spring • Shock absorber • Upper suspension locator and steering pivot Strut Mounts • •... throttle position – Some systems are automatic while others allow drivers to select modes – Reduces body roll but does not eliminate it Types of Electronic Suspensions • Adaptive Systems – Typically