Why Upgrade to H&R Sport Springs on Your A45 AMG?

The Mercedes-AMG A45 is already a performance powerhouse, but its factory suspension prioritizes comfort and compliance. Swapping the stock springs for H&R Sport Springs transforms the car’s character: lower center of gravity, reduced body roll, sharper turn-in, and a more planted feel at speed. The drop is typically around 1.2 to 1.4 inches (30–35 mm) front and rear, which not only improves aerodynamics but also gives the A45 a more aggressive stance. H&R uses progressive-rate wire design, meaning the springs stiffen progressively under load—so daily ride quality remains livable while cornering forces are met with firm support. This guide provides a thorough, step-by-step installation process, from gathering tools to final alignment checks.

Tools and Materials Required

Before you lift the car, assemble everything you’ll need. Having the right tools on hand prevents interruptions and ensures safety throughout the job.

  • H&R Sport Springs (part number specific to your A45 AMG generation) – Verify compatibility with your model year (W176 or later).
  • Floor jack and two pairs of jack stands – A low-profile jack is recommended for the A45’s ground clearance.
  • Metric socket set (10 mm, 13 mm, 15 mm, 16 mm, 18 mm, 21 mm) – For suspension bolts, strut top mounts, and lug nuts.
  • Combination wrench set – 13 mm, 16 mm, 18 mm, and 21 mm are most used.
  • Spring compressor (internal or external type) – Critical for safely removing and installing coil springs. Never attempt the job without one.
  • Torque wrench (0–150 ft-lb range) – Precision tightening to factory specs is mandatory for safety.
  • Pry bar or long flathead screwdriver – To align suspension components during reassembly.
  • Rubber mallet – Useful for loosening stubborn bolts or seating components.
  • Penetrating oil (e.g., WD-40 or PB Blaster) – Apply to bolts the night before to ease removal of corroded fasteners.
  • Safety glasses and mechanic’s gloves – Non-negotiable for protection.
  • Zip ties and shop rags – To secure brake lines or ABS sensors out of the way.

Before You Begin: Preparation and Safety

Proper preparation reduces risk and speeds the installation. Park on a level, hard surface. Engage the parking brake and place wheel chocks behind the rear wheels if working on the front first. Allow the engine and suspension to cool completely—hot components can cause burns. Write down your planned sequence: front springs first or rear?

Many choose to do one axle at a time to maintain a reference point for reassembly.

Identify the correct jacking points on your A45: the front jacking point is under the chassis rail near the front subframe, the rear is near the rear subframe. Never jack on the floor pan. Place jack stands under the designated lift points, typically the pinch welds with rubber adapters or the subframe bolts. Shake the car after lowering onto stands to ensure stability.

Step-by-Step Installation: Front Springs

1. Lift and Secure the Vehicle

Jack the front of the car by the central front subframe crossmember, or lift one side at a time using the pinch weld jack point. Place jack stands under the front subframe or control arm mounts. Remove the front wheels using a 21 mm socket. Set wheels aside with lug nuts threaded loosely onto the studs to avoid losing them.

Using a 16 mm wrench and a 5 mm Allen key, remove the nut and bolt securing the sway bar end link to the strut. This frees the strut assembly from the anti-roll bar and allows the suspension to droop. If the bolt is stubborn, apply penetrating oil and use a breaker bar.

3. Remove the Strut Assembly

Loosen the three top mount nuts (13 mm) located under the hood, but do not remove them yet. From below, unbolt the two lower strut bolts (18 mm) that connect the strut to the steering knuckle. Use a pry bar to gently separate the strut from the knuckle if needed. Support the strut assembly, then remove the three top mount nuts and carefully lower the strut out of the wheel well.

4. Compress the Spring

Place the strut assembly in a bench vise. Attach the spring compressor according to the manufacturer’s instructions. Compress the spring evenly—compress both coils simultaneously, alternating between the two compressor hooks. Compress only enough to relieve tension from the top mount. Never fully collapse the spring; leave a few coils visible.

5. Disassemble the Factory Strut

Use a 21 mm socket to remove the top nut while holding the piston rod with a hex key (size depends on strut brand—typically 5 mm or 6 mm). Remove the top mount, bearing plate, and upper spring seat. Carefully lift the compressed factory spring off the strut. Note the orientation of the spring seat and isolator for reassembly with the H&R spring.

6. Install the H&R Spring

Place the new H&R Sport Spring onto the strut, ensuring the lower coil end sits in the spring perch correctly. H&R springs often have a colored stripe (e.g., red or blue) indicating the progressive rate orientation—check the included instructions. Reinstall the upper spring seat, bearing plate, and top mount. Tighten the top nut to 30 ft-lb (consult your A45 service manual for exact spec). Release the spring compressor slowly and evenly, making sure the spring is fully seated.

7. Reinstall the Strut Assembly

Slide the strut assembly back into the vehicle. Guide the top mount studs through the tower holes. Hand-tighten the three top mount nuts to 18 ft-lb. Reconnect the lower strut to the steering knuckle. Install the two lower bolts and torque to 75 ft-lb.

Reattach the sway bar end link; torque the nut to 40 ft-lb. Repeat for the opposite side.

Step-by-Step Installation: Rear Springs

The rear springs are separate from the shock absorber—simpler to swap but still requires care.

1. Lift and Support the Rear

Jack the rear of the car at the rear differential (for 4MATIC) or the subframe crossmember. Place jack stands under the rear subframe or trailing arm mounts. Remove rear wheels.

2. Disconnect Lower Shock Absorber

Using a 16 mm socket and wrench, remove the lower bolt securing the shock absorber to the rear knuckle. This allows the suspension to droop enough to extract the spring. For easier access, also disconnect the sway bar end link (16 mm nut/5 mm Allen).

3. Remove the Factory Spring

Push down on the rear control arm using a pry bar or your foot (while wearing sturdy boots). Slide the factory spring out of its lower and upper seats. Note the rubber isolator pads—they may be stuck. Transfer these to the new spring.

4. Install the H&R Spring

Place the new spring into the upper spring seat, ensuring the tapered end aligns correctly. Lower the control arm gently and guide the spring into the lower seat. It may be necessary to compress the spring slightly with a spring compressor or use a ratchet strap to ease installation—never force the spring into place. Reconnect the lower shock bolt and torque to 55 ft-lb. Reattach the sway bar end link, torque to 40 ft-lb.

5. Repeat for Opposite Side

Rear springs must be replaced in pairs. Perform the same process on the other side.

Installation Tips for a Smooth Job

  • Mark alignment – Before disconnecting any suspension components, mark the position of the strut lower bolts relative to the knuckle with a paint pen. This helps maintain rough alignment so you can drive to the alignment shop.
  • Use new hardware – H&R recommends replacing the top mount nuts and strut bolts with new ones to ensure proper clamping force. Torque-to-yield bolts should never be reused.
  • Anti-seize on threads – Apply a small amount of copper anti-seize to all bolts to prevent corrosion, but keep it off brake components.
  • Check clearance – After lowering, inspect the tires’ clearance to the fender and suspension arms at full lock and full compression. If you run aftermarket wheels with offset, ensure no rubbing occurs.
  • Double-check spring seating – Spin the spring after releasing the compressor to ensure it sits flat in the perch. A mis-seated spring can cause noise and premature wear.

Final Checks and Post-Installation Steps

After both axles are complete, perform the following:

  • Torque all fasteners – Go back and verify every bolt is tightened to factory specifications. Pay special attention to control arm bolts, sway bar links, strut top mounts, and lug nuts. Refer to a trusted torque sheet for the A45 AMG (available from Mercedes-specific forums).
  • Reinstall wheels – Torque lug nuts to 110 ft-lb in a star pattern.
  • Lower the vehicle – Lower off jack stands and let the suspension settle. Then drive the car slowly for a few feet and re-check ride height. The springs will settle another 1/4 inch over the first 100 miles.
  • Professional alignment – H&R springs change the suspension geometry. You must get a four-wheel alignment immediately. Target specifications: front camber -1.2° to -1.5°, rear camber -1.5° to -2.0°, toe 0.1° total toe-in front and rear. A reputable alignment shop can adjust toe, but camber may require aftermarket camber plates. Schedule an appointment per H&R’s alignment recommendations.
  • Break-in period – Drive gently for 200-300 miles to allow the springs to settle. Avoid full suspension compression or heavy loads until after the break-in.
  • Inspect for noises – Listen for creaks, clunks, or rattling. Common causes: loose top mount nuts, mis-seated spring isolators, or interference between the spring and control arm. Address immediately.

Common Pitfalls to Avoid

  • Using spring compressor on the car without removal – On the rear, attempting to compress the spring while it’s installed can be dangerous and damage components. Always remove the spring from the vehicle for this operation.
  • Overtightening the strut top nut – The top nut must be tightened to spec (around 30 ft-lb). Too tight can damage the bearing or strip the piston rod. Always use a torque wrench.
  • Skipping the test drive before alignment – Let the suspension settle under its own weight. If you align immediately after installation, the settings will change as the springs settle.
  • Mixing up left and right springs – H&R springs are often side-specific due to spring seat orientation. Check the part number printed on the side.

Performance Gains and What to Expect

After installation and alignment, you’ll immediately notice reduced body roll in corners—the A45 feels more planted and responsive. The ride is firmer, but the progressive spring rate absorbs small bumps reasonably well. At the track or on twisty roads, the car rotates more willingly under throttle, and braking stability improves. The lower center of gravity also reduces high-speed float. Some owners report a slight increase in tire noise due to the firmer suspension transmitting more road vibration, but this is typical with any sport spring upgrade.

For optimal results, pair H&R springs with upgraded dampers (e.g., Koni or Bilstein) after the factory shocks wear out.

Conclusion

Installing H&R Sport Springs on your Mercedes-AMG A45 is a rewarding DIY project that dramatically enhances handling and aesthetics. With careful preparation, the right tools, and this detailed guide, you can complete the swap safely and efficiently. Remember to follow torque specs, allow the springs to settle, and invest in a professional alignment. Your A45 will reward you with sharper, more connected driving dynamics. For additional technical resources, visit the H&R official site and the MB workshop manual portal for official service procedures.