• AST Suspension 5100 Series Coilovers (Excludes Front/Rear Top Mounts) - 1985-1991 BMW 3 Series 325i (E30)
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AST 5100 Series Coilovers | BMW 3 Series E30 (85-91) (ACU-B1501S)

AST 5100 Series Coilovers | BMW 3 Series E30 (85-91) (ACU-B1501S)

ACU-B1501S

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The AST 5100 Series Coilovers for the BMW 3 Series E30 (1985-1991) are high-performance suspension components designed to enhance handling and stability. Featuring inverted shock absorber technology, these coilovers utilize race-proven upside-down damper design that offers increased strength and durability. The design improves suspension geometry under heavy lateral and braking forces, making them ideal for spirited street driving and track use. The coilovers provide adjustable rebound damping via a single knob, allowing for precise tuning to match driving preferences and conditions. Constructed with high-quality materials, these coilovers deliver improved ride quality, reduced body roll, and enhanced responsiveness compared to standard twin-tube shocks.

Designed specifically for 1985-1991 BMW 3 Series E30 models, including the 325i variant, these coilovers are a direct bolt-on upgrade for compatible chassis. They are suitable for enthusiasts seeking performance improvements on both street and track applications. Installation involves replacing the factory shocks with these coilovers, offering a straightforward upgrade for improved handling and ride height adjustment. The kit includes the necessary coilover units and mounting hardware. These coilovers are ideal for drivers looking to optimize their E30’s suspension for aggressive driving, track days, or improved daily handling.

Overview

The 5100 Series shock absorbers for the 1985-1991 BMW 3 Series 325i (E30) utilize inverted / upside down technology. The inverted design is race proven technology and produces an extremely strong damper, providing better suspension geometry under heavy lateral and braking loads as seen in a road and track environment.

The 5100 Series shock absorbers give your car a better performance than the standard twin tube design. With the 5100 Series suspension you can adjust rebound with one knob. The adjust platform allows you 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.

Features

  • Floating piston design with high pressure nitrogen means no cavitation around the piston.
  • 14mm diameter internal shaft.
  • 44.5 mm diameter shaft struts, inverted.
  • Steel cylinder body shocks, inverted.
  • High end, track ready suspension.
  • 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.
Specifications
  • Part Number: ACU-B1501S
  • Product: AST 5100 Series
  • Adjustment: 1 Way
  • System: Separate Setup
  • Product Note: Non Coilover
  • Front/Rear Ratio: Front = 70% / Rear = 30%
  • Strut/Shock Type: Front: Uses OEM spindles / Rear: Eye 2 pin strut
  • Model Years: 1985-1991
  • Make: BMW
  • Model: 3 Series
  • Chassis: E30
  • Spring Kit: Included
  • Top Mounts: Front / Rear Optional (If Available)
  • Optional 1 Front Top Mounts: TMA-B02-A1-20F - Camber adjustable
  • Optional 2 Front Top Mounts: Not Available
  • Optional Rear Top Mounts: TMA-B01-B1-30R - Solid top mounts (no camber adjustment)
  • Adjustable Front Droplinks Available? No
  • Adjustable Front Droplinks Required? No
  • Adjustable Rear Droplinks Available? No
  • Adjustable Rear Droplinks Required? No
  • DDP Pistons Included? No
  • DDP Pistons Available? Yes
  • DLC Coated Shafts Included? No
  • DLC Coated Shafts Available? Yes
  • QDC Included? No
  • TUV Approved?
  • Comments: We recommend using OE top mounts. Original front spindles needed before start of production.
Vehicle Fitment
  • 1985 BMW 3 Series 325i (E30)
  • 1986 BMW 3 Series 325i (E30)
  • 1987 BMW 3 Series 325i (E30)
  • 1988 BMW 3 Series 325i (E30)
  • 1989 BMW 3 Series 325i (E30)
  • 1990 BMW 3 Series 325i (E30)
  • 1991 BMW 3 Series 325i (E30)
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