Have you ever heard of BMW’s Dynamic Drive system? Whereas most car suspensions either corner well or give you a pleasant time while driving in a straight line, the German car maker’s suspension system gives you the best of both worlds.
When you go around a corner, the car tilts away from the direction it’s going. The sway bar counteracts this tendency. Also called an anti-roll bar or stabilizer bar, the sway bar connects the front wheels. When you turn around a corner, the sway bar twists, generating resistance that helps prevent the car from tilting too much.
Unfortunately, the sway bar stiffens the suspension during straight-line driving, making handling more difficult. It also produces unnecessary resistance if a wheel bounces to the side. Even if you only hit a bump on the road, the sway bar reacts like you’re making a turn.
BMW counteracted this drawback by using a variable stiffness sway bar in its Dynamic Drive system. This proprietary stabilizer bar design enables the Direct Drive system to respond appropriately to how you drive.
By reducing body roll, the Dynamic Drive system makes driving safer and more pleasant. It improves the car’s stability and tire traction. Finally, the active sway bar system reduces tire wear, helping the tires last longer.
Dynamic Drive is BMW’s proprietary active stabilizer bar system, an improved version of the sway bar system in many vehicles.
Other companies have counterparts to BMW Dynamic Drive. Toyota offers the Active Power Stabilizer Suspension System (APSSS). Meanwhile, Lexus has the Kinetic Dynamic Suspension System (KDSS).
A BMW Dynamic Drive System is comprised of an active sway bar, hydraulic pump, electro-hydraulic valve block, fluid reservoir and level sensor, hydraulic valves, lateral acceleration sensor, and dynamic drive control unit.
Arguably the most important part of the Dynamic Drive, the variable stiffness sway bar is divided into two halves or individual sway bars that can move independently. Half of the bar connects to the motor housing, while the other half attaches to a hydraulic oscillating motor.
The hydraulic motor is driven by pressure from the power steering pump. Pressure valves and the dynamic drive valve block actuate the motor.
The two halves of the variable stiffness sway bar turn in opposite directions. On the outside of a curve, the motor housing moves upward. On the inside of a curve, the housing moves downward.
The Dynamic Drive system disconnects the variable stiffness sway bar during straight-line driving. When turning around corners, the system reconnects the sway bar to generate resistance that reduces the rolling effect.
Thanks to the variable stiffness sway bar, Dynamic Drive can soften or tighten the front and rear independently. Its computer can constantly adjust the sway bar to avoid understeer or oversteer.
The hydraulic pump drives the power steering and the dynamic drive valve body. It steadily maintains high pressure on the valve body, enabling the Dynamic Drive system to rapidly move hydraulic fluid to and from the sway bars. The pump features hydraulic pressure hoses and an accumulator bulb.
The valve block operates like the valve body in an automatic transmission. With electronic solenoids and hydraulic valves, the block regulates the movement of hydraulic fluid to the sway bars. It can stiffen the sway bar while cornering. Conversely, it can soften the bar during straight-line driving.
The reservoir stores the hydraulic fluid used in the Dynamic Drive system. It also pulls double duty as the power steering reservoir.
There’s a level sensor that measures the quantity of fluid in the fluid reservoir. If it detects low fluid levels, refill the reservoir with the manufacturer-approved Pentosin CHF-11S fluid.
The valve block has many hydraulic valves that actuate various parts. Other valves also appear outside the block.
For example, the front and rear subframes have pressure control valves that change actuation pressure. Next is the directional valve that changes where the high-pressure fluid flows.
Meanwhile, the front sway bar has a vent valve that admits air into the hydraulic pump. It prevents cavitation on extremely rough surfaces that can interfere with the stabilizer bar.
Finally, the fail-safe valve shuts off the mechanism that adjusts the sway bar, effectively converting it to a standard stabilizer bar.
The lateral acceleration sensor measures how fast and how much the BMW tilts laterally or sideways when going around the corner. It sends its readings to the Dynamic Drive control unit.
This is the computer that controls the Dynamic Drive system. It collects the readings from the lateral acceleration sensor, DCS module, and steering angle sensor. Based on the information, the control unit uses the electro-hydraulic valve block to adjust how the sway bars work.
Dynamic Drive is an option for new-build BMW 5, 6, and 7. It has also been available for the BMW X5 and X6 since 2001.
But what if you got your BMW from someone else, and the seller isn’t sure if it has Dynamic Drive? The simplest way is to check the sway bar under your car.
The BMW Dynamic Drive system is distinguishable from the typical sway bar system in several ways. First and most obviously, its active sway bar looks like a pair of connected bars instead of a single bar.
Next, you can find the motor housing in the system’s center. The silvery part stands out.
You can also inspect the power steering pump for a pressure accumulator, a small part that resembles a light bulb.
Finally, check the power steering reservoir. The Dynamic Drive features a long, tall cylinder.
You can also look for a trustworthy online VIN decoder and enter the last 7 digits of your BMW’s vehicle identification number (VIN). If the encoder shows the S229A code and mentions Dynamic Drive, your car has the active sway bar technology.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.