AST Suspension

AST Suspension 5100 Series 1-Way Coilovers (Non Inverted - Front and Rear Top Mounts Not Included) ACS-B1601S - 2005-2011 BMW 330i (E90-E91-E93)

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The 5100 Series shock absorbers for the 2005-2011 BMW 330i (E90-E91-E93) utilize non-inverted / high performance monotube technology. In the past, these were known as the 4100 series. Monotube design shocks absorbers give your car a better performance than the standard twin tube design, the gas pressure is separated by a floating piston, and eliminates cavitation and airation within the oil chamber.

The 5100 Series shocks allow rebound adjustment with one knob. The adjust platform allows the user to adjust the ride height of your car. AST suspension shock bodies are specially designed to keep maximum stroke, even with a lower ride height.

How a Monotube design works?

Monotube design is essential for performance. The oil and nitrogen are separated by a floating piston, and allows the use of a larger piston, increasing the damper performance and sensitivity felt by the driver, all this added together produces more grip, gives more control and driver feedback from your vehicle.

What is a rebound adjustment?

Rebound controls the rate of extension of your shock absorber. By changing the rebound you can directly change the characteristics of the vehicle.


  • Floating piston design with high pressure nitrogen means no cavitation around the piston.
  • 22mm / 14mm diameter shaft struts, non-inverted
  • Steel cylinder body shocks, non-inverted.
  • Rebound adjustable ('Singles').
  • Low friction seal.
  • Adjuster knobs permanently mounted on the dampers.
  • Designed to use OEM top mounts.
  • Rubber bushings for 'eye' shock mounts.
  • Includes springs.
  • Rebuildable.
  • Optional spherical top mounts.
  • Optional DLC (diamond like carbon) coated shafts.
  • Optional DDP (double digressive piston).
    • Double Digressive Pistons are recommended for use on the non-driven wheels.
    • 4WD/FWD vehicles: DD pistons for both rear axle struts/shocks.
    • RWD vehicles: DD pistons for both front axle struts/shocks.
  • Optional custom valving.

Product Specifications

  • Part Number: ACS-B1601S
  • Product: AST Suspension 5100 Series 1-Way Coilovers
  • Adjustment: 1-Way
  • System: Non Inverted, Old 4100 Series
  • Product Note:
  • Front/Rear Ratio: Front = 60% / Rear = 40%
  • Strut/Shock Type: Front: Clamp McPherson strut / Rear: Pin 2 pin strut
  • Model Years: 2005-2011
  • Make: BMW
  • Model: 330i
  • Chassis: E90-E91-E93
  • Spring Kit: Included
  • Top Mounts: Front And Rear Are Not Included
  • Optional 1 Front Top Mounts (Additional Cost): TMA-B01-A1-20F - Camber adjustable
  • Optional 2 Front Top Mounts (Additional Cost): Not Available
  • Optional Rear Top Mounts (Additional Cost): Not Available
  • Adjustable Front Droplinks (Additional Cost): Part Number: DLA-BMW2-S
  • Adjustable Front Droplinks Required? Yes
  • Adjustable Rear Droplinks Available? No
  • Adjustable Rear Droplinks Required? No
  • DDP Pistons Included? No
  • DDP Pistons Available (Additional Cost): Yes
  • DLC Coated Shafts Included? No
  • DLC Coated Shafts Available (Additional Cost): Yes
  • QDC Included? No
  • TUV Approved?
  • Comments: Works with OE top mounts.

Vehicle Fitment

  • 2005 BMW 330i (E90-E91-E93)
  • 2006 BMW 330i (E90-E91-E93)
  • 2007 BMW 330i (E90-E91-E93)
  • 2008 BMW 330i (E90-E91-E93)
  • 2009 BMW 330i (E90-E91-E93)
  • 2010 BMW 330i (E90-E91-E93)
  • 2011 BMW 330i (E90-E91-E93)

Product information