1999-04 Cobra, Bilstein HD series damper package for IRS-equipped Mustang, includes 2 Bilstein HD struts and 2 Bilstein HD shocks, with integral progressive bumpstops.

• Struts are suitable for both stock-location springs and coil-over conversions. See chart below for spring recommendations.
• Rear shocks may be modified for a coil-over conversion by machining a groove in the shock body. Order package number BIL-9.1 (with its pre-grooved shocks) if a future rear coil-over conversion is a possibility.
• Includes V36-4138-H5 front struts
• Includes BE5-2959-H0 rear shocks

For more details and technical information, scroll down.

• Firm, yet good ride quality, as is expected of a performance car
• Bilstein struts and shocks are made with patented mono-tube technology
• Inverted strut design has very large strut shaft bushings for greater resistance to deflection from cornering loads, and protection of the oil seal
• High nitrogen gas pressure prevents oil foaming and resultant fading
• Monotube design has better heat dissipation than twin-tube dampers, keeps the oil cooler, and decreases heat-induced damper fade
• Velocity-sensitive valving improves ride quality
• Each Bilstein strut and shock is tested on a shock dyno
• The Bilstein rear IRS shocks in this package may be grooved for coil-over conversions, and come with an integral, progressive bump stop
• Bilstein struts and shocks include dustcovers
• MM Sport series and MM Race series dampers are better suited for more aggressive spring rates.

Tech
Heavy Duty (HD) Bilsteins work very well in street applications with a variety of both conventional springs and coil-over conversions. They are designed to deliver the best possible ride quality coupled with impressive street performance. The HD series dampers were not designed for use with overly aggressive spring rates, particularly in coil-over conversions. For dampers more suited to aggressive spring rates, see the MM Sport series and MM Race series dampers.

The HD series rear shocks must have a groove machined in the shock housing to accept the MM rear coil-over conversion kit. To obtain grooved shocks, either order package number BIL-9.1, or rear shocks part number GBE5-2959-H0.

While they are non-adjustable, Bilstein's unique deflective-disc valve design instantaneously self-adjusts to changing road surfaces. Their performance does not degrade with age, usage, or heat, requiring no compensating manual adjustments as with other brands. Bilstein uses a patented mono-tube design that allows for a larger piston size than is possible with a twin-tube damper. The mono-tube design provides better heat dissipation to keep the damper's oil cooler, and decreases heat-induced damper fade. High-pressure nitrogen gas prevents oil foaming and fading. The unique inverted design of the Bilstein strut allows for very large strut shaft bushings, which are less prone to deflection. The inverted strut design also keeps the oil seal protected from the elements. Every Bilstein damper is tested on a shock dyno before leaving the factory to ensure quality.

All Bilstein struts and shocks include dustcovers suitable for use with conventional springs. Front coil-over applications require unique smaller dustcovers that are included with MM front coil-over conversion kits, and are also available separately.

Tech links

• Choosing the right damper
• What's a "damper"?
• Adjustable vs. non-adjustable dampers
• Matching spring rates with dampers
• Spindle swapping tech