1999-04 Cobra Mustang, Bilstein HD series IRS shock, with groove for coil-over conversion kit, dust boot and integral bumpstop.
If you do not already have, or purchase now, an MM rear coil-over conversion kit, you must add urethane shock eye bushings MMSM-105 to install this grooved rear shock.

Included in this shock's price is a charge for grooving it for a coil-over conversion. You can get up to a $60 discount ($30 per shock) if:

• You purchase a rear coil over kit along with your shocks.
• In the past you purchased a rear coil-over kit directly from us.
• You purchase a rear coil over kit directly from us at a later time.

If any of these situations apply, please note it in the "special instructions" field at checkout. We will confirm the situation and waive the grooving charge when we process your order.

• Suitable for both stock-location springs and coil-over conversions. See chart below for spring recommendations.

For more details and technical information, scroll down.

• Firm, yet good ride quality, as is expected of a performance car
• Includes a machined groove for a coil-over conversion
• Does not include lower eyelet bushings, as urethane bushings are included in an MM Rear Coil-over Conversion Kit. To install without a coil-over kit, order bushing kit MMSM-105
• Bilstein struts and shocks are made with patented mono-tube technology
• 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
• Includes 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.

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. 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.

Tech links

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