Upgrading your Mercedes-AMG CLA45 with H&R Sport Springs is one of the most effective suspension modifications you can make. These springs lower the center of gravity, reduce body roll, and sharpen turn-in response without sacrificing daily drivability. The result is a more aggressive stance and a noticeably tighter connection to the road. This guide provides a comprehensive, step-by-step walkthrough for a safe and successful installation, covering front and rear spring replacement, torque specifications, alignment considerations, and common pitfalls to avoid. Whether you are an experienced DIYer or a first-time modifier, following these instructions will help you achieve professional-level results in your own garage.

Tools, Materials, and Safety Equipment

Before beginning, gather all necessary tools and components. Having everything within reach will prevent interruptions and ensure you can work through the process methodically. Safety is paramount when dealing with compressed springs and heavy suspension components, so do not skip any protective gear.

Required Parts

  • H&R Sport Springs (part number specific to CLA45 AMG, typically 29344-1)
  • New strut mount hardware (recommended: upper strut nuts and isolator bushings)
  • Anti-seize compound for threaded fasteners

Tool List

  • Floor jack (minimum 2-ton capacity)
  • Two heavy-duty jack stands (3-ton capacity recommended)
  • Metric socket set with extensions (10mm, 13mm, 15mm, 16mm, 18mm, 21mm, 22mm)
  • Torque wrench (1/2-inch drive, 20–150 ft-lb range)
  • Spring compressors (wall-mounted or external screw-type for safety)
  • Pry bar or heavy-duty flathead screwdriver
  • Breaker bar for stubborn bolts
  • Rubber mallet
  • Wire brush for cleaning threads
  • Safety glasses and mechanic’s gloves

Preparation and Vehicle Setup

Park the CLA45 on a level, hard surface. Engage the parking brake and chock the rear wheels if you are working on the front. Allow the engine and suspension to cool completely if the car has been driven. For the best access, you will need to lift each axle separately and support the chassis on jack stands placed on the factory lift points. Never trust a jack alone to hold the vehicle.

Removing the Wheels

Loosen the lug nuts while the wheels are still on the ground. Lift the axle, place jack stands under the frame rails or designated lift points, then fully remove the lug nuts and pull off the wheels. Store them safely out of the work area. With the wheels removed, clean any dirt or debris from the exposed suspension components using a spray cleaner or simple green and a rag. This reduces the chance of contamination entering the strut assembly.

Rear Spring Installation (Easier Side, Start Here)

Many guides begin with the front, but the rear is simpler and builds confidence. The CLA45 uses a multilink rear suspension; the spring is separate from the shock absorber, which makes removal and installation less complex.

Use a 15mm socket to remove the nut on the sway bar link. This disconnects the link from the control arm. You may need a hex key to hold the link stud while loosening the nut. A pry bar can help guide the link out of the hole.

2. Support the Control Arm and Remove the Shock

Position the floor jack under the lower control arm near the spring seat. Slightly compress the suspension to take tension off the shock. Remove the lower shock bolt (18mm). Then remove the upper shock mount nuts (13mm) accessible from inside the wheel well or trunk lining. On the CLA45, the upper mount is accessed by pulling back the trunk side carpet. Carefully lower the control arm with the jack to relax the spring. Remove the old spring and its upper rubber isolator. Compare the isolator to the H&R spring seat; transfer the rubber if it is not included.

3. Install the H&R Sport Spring

Place the new H&R spring onto the lower control arm seat, ensuring the pigtail (end of the coil) aligns with the notch in the seat. Place the upper isolator on top, then slowly raise the control arm with the jack until you can reattach the shock. Guide the shock into its upper mount, loosely install the nuts, then install the lower shock bolt. Torque the lower bolt to 66 ft-lb and the upper nuts to 26 ft-lb. Reconnect the sway bar link, torquing to 41 ft-lb. Repeat on the other side.

Front Spring Installation (Requires More Disassembly)

The front strut assembly is a McPherson-type unit, meaning the spring is integrated with the shock. Compressing the spring safely is absolutely critical. The H&R springs are shorter than OEM, so proper spring compressor use is non-negotiable.

1. Remove the Front Strut Assembly

Start by removing the ABS sensor wire from the strut housing and unclip it from the bracket. Remove the brake line bracket bolt. Then, working from the top of the strut tower under the hood, remove the three 13mm nuts holding the strut mount to the chassis. Under the car, remove the two 21mm bolts connecting the strut to the steering knuckle (these are often very tight; use a breaker bar and penetrating oil if needed). Lower the lower control arm slightly to free the strut assembly. Pull the entire unit out from the wheel well. A second set of hands can help guide it past the axle shaft.

2. Compress the OEM Spring and Disassemble

Place the strut assembly in a spring compressor. Follow the manufacturer’s instructions carefully. Compress the spring evenly until all tension is removed from the upper mount. Remove the top nut (21mm or 22mm, depending on year) while holding the strut piston rod with a hex key (6mm or 7mm). Slide off the upper mount, bearing plate, dust boot, and bump stop. Unhook the compressed OEM spring and set it aside.

3. Install the H&R Sport Spring

Position the new H&R spring on the strut. It must sit in the lower spring perch with the coil end indexed to the step. Slide on the old dust boot and bump stop if they are in good condition; if worn, replace them. Reinstall the upper mount and bearing assembly. Tighten the top nut to the manufacturer’s specification—typically 47 ft-lb, but check your vehicle’s service data. Slowly release the spring compressor, ensuring the spring seats evenly. Torque the top nut again after release. Reinstall the strut assembly in reverse order of removal. Tighten the three top mount nuts to 15 ft-lb. Tighten the two knuckle bolts to 74 ft-lb. Reattach the ABS sensor and brake line bracket.

Final Assembly and Wheel Installation

With all four springs installed, inspect all hardware for correct torque. Double-check that sway bar links are secured, shock mounts are tight, and no bolts were left loose. Clean the wheel hubs with a wire brush to ensure the rotors seat flat. Mount the wheels and hand-tighten the lug nuts. Lower the vehicle completely to the ground. Torque the lug nuts in a crisscross pattern to 110 ft-lb (check your owner’s manual for exact value, typically between 110–115 ft-lb for this chassis).

Post-Installation Checklist and Test Drive

1. Inspect Clearance

Turn the steering wheel lock-to-lock and check that no tire or wheel contacts the fender liner, control arms, or sway bar. The CLA45 with H&R springs typically drops 1.3 inches front and 1.0 inch rear, so clearance should be adequate with factory wheels. If you have aftermarket wheels with aggressive offset, a test fit before driving is essential.

2. Perform a Test Drive

Drive slowly over speed bumps and listen for any clunks or rubbing. Accelerate gently, brake smoothly, and take a few turns at moderate speed. The car should feel noticeably more planted and responsive. If you hear spring noise or binding, re-check upper mount orientation and spring seat alignment. A slight squeak can indicate the spring needs a rubber isolator or the bearing is misaligned.

3. Alignment is Mandatory

After any spring change, the vehicle’s camber, caster, and toe settings will shift. Obtain a professional four-wheel alignment immediately. The CLA45 front camber is not adjustable from the factory, but toe can be set. A good alignment shop can often achieve a slight positive caster increase for better straight-line stability. Expect to pay between $100–$150 for a quality laser alignment. Driving without an alignment will cause uneven tire wear and degrade handling.

Common Pitfalls and Pro Tips

  • Stripped strut top nut: Always use a hex key to hold the piston rod. If the rod spins, the nut will gall and strip. Apply blue Loctite to the nut threads.
  • Compressor slipping: Use spring compressors with safety pins or retaining clips. Never overtighten; compress only enough to relieve load.
  • Rear spring orientation: H&R rear springs have a tapered end. That tapered end points upward toward the chassis mount. Installing upside down can cause noise and improper load distribution.
  • Torque specifications vary by model year: Always consult a factory service manual or reliable datasheet like this reference from Pro Street for your specific year.
  • Allow settling time: The springs will settle 0.25 to 0.5 inches lower after 100–200 miles. The ride height immediately after installation will be slightly higher than the final stance.

Why Upgrade to H&R Sport Springs?

H&R has been a leader in automotive suspension for decades. Their proprietary cold-coil steel is shot-peened and double-scragged for consistent spring rate and minimal fatigue. The CLA45 AMG chassis benefits from a lower center of gravity and increased spring rates over the factory setup, reducing understeer and improving steering feedback. Many owners report a 15–20% reduction in body roll during cornering while maintaining a ride quality that is firm but compliant for daily driving. For a dedicated track build, pairing these springs with adjustable dampers like Koni Yellows or Bilstein B6 is a popular next step. You can read more about the product line on the H&R official website.

Conclusion

Installing H&R Sport Springs on your CLA45 AMG is a highly rewarding project that delivers measurable improvements in both looks and handling. By following this detailed guide, including proper spring compression, torque procedures, and alignment requirements, you can complete the installation safely and confidently. The time invested in meticulous assembly pays off every time you take a corner or glance back at the lowered stance. For ongoing discussion and community support, forums like MBWorld offer valuable owner experiences and troubleshooting advice. Drive safely and enjoy your enhanced AMG.