Air suspensions have been a common feature in the upper mid-range segment for some time. While older BMW 5 Series Touring models (E39, E61, F11) employed separate air suspension bellows and dampers, modern systems integrate both components into a single, highly coordinated unit on the rear axle.

The BMW 6 Series GT “hatchback”, introduced in November 2017, is another vehicle equipped with air suspension struts on the rear axle. Recently, we received a request from a BMW 640i driver, Christian S. He had moderately lowered his rear-wheel drive car by using a lowering spring set on the front axle and a shortened articulated rod on the rear axle.

Consequently, the vehicle owner had been deprived of the driving enjoyment typically associated with a BMW 640i GT. A test drive by our head of R&D and driving test, Thomas Wurst, confirmed that the GT fell short of its Gran Turismo reputation.

The moderate lowering eliminated rear axle suspension travel. The standard dampers were unable to cope with the increased spring rate of the air suspension, and the shock absorbers reached their maximum compression due to the reduced spring travel. This issue often arises when software modifications are applied to lower standard air suspension systems.

Anyone familiar with this topic knows that the chassis electronics attempt to compensate for reduced suspension travel, caused by conventional lowering with an articulated rod, by increasing air pressure. This results in elevated air pressure within the air bellows, leading to a stiffer ride and suboptimal performance from the standard damper, which often accelerates wear.

A chassis designed for lowering is undoubtedly superior. However, removing the complex air suspension system, including its compressor and sensors, is impractical. True to KW’s innovative spirit, we’ve developed an alternative solution for vehicles like the BMW 6 Series GT (G32) mentioned earlier.

A new feature of our KW V3 coilover suspension (formerly KW Variant 3), now available for the BMW 6 Series Gran Turismo (G32), is its compatibility with the standard rear axle air suspension. We’ve adapted our independently adjustable compression and rebound dampers to work seamlessly with the OEM air suspension system. This involved shortening our dampers and optimizing suspension travel to match the original setup.

To install the KW V3 rear axle damper, the OEM air bellows are removed from the original shock absorber using our provided tool. The air suspension is then lowered using our special lowering rods. This process maintains the original suspension travel of the BMW 6 Series GT (G32) at stock height.

The BMW G32’s front axle features MacPherson struts with a steel springs. To match this setup, we offer our renowned KW coilover struts with a main spring and helper spring as a retrofit solution. The KW V3 coilover suspension kit (previously known as KW Variant 3), specifically tuned for the BMW 6 Series GT (G32), allows for independent adjustment of compression and rebound damping even after installation.

The rebound low-speed bypass valve, which enhances handling precision, offers 16 adjustment settings. Rebound damping influences the suspension’s rebound speed after compression, directly impacting the BMW 6 Series GT’s road connection.

Regardless of this, the cross-section of the low-speed compression valve can be reduced or enlarged in twelve click stages in order to individually adjust the damping during compression. The compression damping influences the immersion speed of the damper piston rod and thus also the turn-in behavior, pitch and roll of the body.

But what does BMW 6 Series GT driver Christian S. actually think about his G32 with the new KW V3 coilover suspension? Since installing the suspension in early April, he’s already covered 3,000 kilometers. Whether on the highway or tackling fast corners on country roads, his 640i GT now feels significantly safer and more responsive than before.

Christian S. was pleasantly surprised by the G32’s significantly improved road grip and enhanced driving comfort, despite its sportier handling. Having previously experienced the KW V3 coilover suspension in his F11 Touring, he plans to equip his next vehicle with either a KW V3 or Variant 3 system.

The front axle’s infinitely adjustable lowering is achieved through a rotating spring plate and stainless steel shock absorber. On the rear axle, adjustable articulated rods and a 25 millimeter air suspension lowering enable a similar adjustment. The overall lowering range is 30-55 millimeter for the front and 25-55 millimeter for the rear axle.

A 55mm lowering is notably substantial, even with 21-inch wheels. Christian S.’s BMW 640i GT is equipped with BBS CI-R Unlimited wheels in a white gold finish.

BBS Unlimited wheels are uniquely designed with a 5×117.5 bolt pattern. To fit the BMW 6 Series GT (G32)’s 5×112 pattern, precision-engineered wheel hub adapters and centering rings are used.

Christian S.’s GT features 9.5×21-inch BBS CI-R Unlimited wheels with ET72 offset and level 1 concavity on the front axle. The rear axle boasts wider 11×21-inch wheels with the same ET72 offset but a deeper level 2 concavity. To achieve the desired fitment, 50mm hub adapters were used on the front, resulting in an effective ET22 offset. On the rear, 35mm hub adapters were installed, producing a final offset of ET37.

By the way, the BBS CI-R Unlimited is not only available in different colors, but BBS has also launched a nice range of accessories such as collision protection rings, hubcaps, valve caps and much more.

By the way, our colleagues from Chassis Development are currently in the process of developing dampers and coilovers for other vehicle models with standard air suspension, such as the BMW 6 Series GT (G32). If you have not yet found a coilover suspension for your car in our online shop (www.kwsuspensions.net), simply send us a development request directly via our KW homepage.