BC Racing ZR Coilovers BMW 3 Saloon/Coupe RWD (Rear Integrated) E90/E92 (05-11) 5.5/6kg.mm

Key Features

• 3-way adjustable damping controls
• Ride height adjustment separate to spring preload
• Inverted damper design (depending on model)
• Dual Piston design (1 in reservoir, 1 in shock)
• Teflon coated steel braided lines for external reservoir on inverted dampers and solid stem for double A-arm cars
• Tapered bottom mount locking collar to prevent it from working loose
• Pillowball top mounts
• Dust boot to protect the damper seal
• Custom spring rates available
• All spare parts available with short lead times
• 1-year manufacturer warranty

Which kit is right for you?

Corner Weighting Adjustment

The lower spring platform of BC Racing coilovers is adjustable. This feature enables the car to be configured for corner weighting, ensuring perfect balance and maximising tyre efficiency.

It's essential for the car to distribute equal weight on each tyre of an axle, meaning both front tyres and both rears should bear equal loads. This ensures both tyres contribute equally during cornering, enhancing overall grip, maximising cornering speed, and reducing lap times.

Optional assister springs are available for purchase, allowing wheel droop to be adjusted to meet specific requirements.

Ride Height Adjustable

The ride height is set by the position of the coilover bottom mount. This mount can be adjusted up and down the damper body to provide a complete range of adjustment.

Because the ride height is determined by an adjustable bottom mount rather than the spring platform, you maintain full damper travel regardless of the chosen ride height setting.

Damping Adjustment

ZR coilovers boast a 30-way damping adjustment that combines both rebound and compression in one adjuster for simplicity and ease of use. This adjustable feature enables you to fine-tune the vehicle to suit the prevailing conditions.

By adjusting the damping on the front and rear, you can alter the car's handling. For instance, increasing damping force on the rear relative to the front will shift the vehicle into a more oversteer-oriented stance.

If you're aiming for drag racing in a rear-wheel-drive car, you'd want the rear of the car to squat off the line to maximise weight transfer to the rear tyres and thus enhance traction, reducing the likelihood of wheel spin. To achieve this, you would soften the rear dampers to allow faster compression. Conversely, if the rear dampers were set too hard, traction would be reduced.

On the other hand, if you're attempting drifting and struggling to break traction while experiencing understeer, stiffening the rear dampers and softening the front dampers will reduce rear traction while increasing front traction. This will make the rear of the car looser while minimising understeer, thereby altering the vehicle's handling characteristics towards drifting rather than drag racing, road driving, or track driving.

Pillowball (Rose Joint) Upper Mount

Several BC Racing ZR coilovers feature pillowball upper mounts. The mount itself is constructed from aluminium alloy, which is anodised and then bead blasted to achieve a high-quality, durable finish.

The pillowballs are manufactured in Japan, and their solid construction eliminates any flex or play typically associated with standard rubber mounts, thus enhancing response and handling.

Camber Adjustment

If your vehicle allows for camber adjustment, BC Racing coilovers automatically incorporate camber-adjustable aluminium pillowball top mounts. These mounts feature the same high-quality Japanese-manufactured pillowball but offer the added benefit of an adjustable top mount, allowing you to set camber according to your requirements, whether it's for road, track, or drift use.

Corrosion Protection

The damper units are made of black chromed steel to ensure exceptional durability, even in the harshest European winters. The aluminium components, such as top mounts and locking collars, undergo an anodising process, while the steel lower mounts undergo an electrophoretic disposition process followed by powder coating.

Regularly, a random selection of steel components including brackets, dampers, and screws undergo a salt spray test every month to assess the quality of the protective processes and ensure that anti-corrosive properties are maintained at the highest possible standard.

High Quality Coil Springs

BC Racing coilovers exclusively utilise top-grade steel for their spring manufacturing. These springs are crafted from SAE9254 high-strength, durable, cold-wound steel.

Each spring undergoes compression testing, enduring over 500,000 cycles with less than 5% deformation.

Patented Concave Lower Locking Collar

Coilovers utilise a locking collar to prevent the bottom mount from becoming loose. If the bottom mount loosens, the damper body can descend into it, thereby reducing the ride height on that corner, which can lead to hazardous handling characteristics. This is a prevalent issue with coilovers in general.

BC Racing employs an innovative and patented design for the lower locking collar, featuring a bevelled edge that fits into a corresponding bevel in the coilover bottom mount. This significantly increases the surface area that the locking collar operates on, thus preventing the common and hazardous problem of the locking collars coming loose.

High Quality Oil

BC Racing dampers employ an advanced shim stack design and top-notch oil to consistently regulate the compression and rebound speed of the damper rod, even in the most demanding conditions.

As the vehicle traverses uneven terrain, the compression and rebound movements of the damper rod heat up the oil. Lower-quality dampers utilise inexpensive oil with characteristics that change with fluctuating temperatures. It's crucial to use high-quality oil capable of maintaining consistent viscosity across a wide temperature range. Once the oil begins to degrade, its properties shift, resulting in changes to damping and subsequently altering the vehicle's handling characteristics.

BC Racing ensures the use of only premium-quality oil to maintain damping rates not only during immediate usage (such as during spirited driving on back roads or on the track) but also to maximise long-term durability with oil that resists rapid degradation over time, thereby significantly extending the damper's operational lifespan.

Nitrogen Pressurised Dampers

When you push a damper hard on the track or on high-speed bumpy roads, you can induce aeration in the oil, leading to cavitation. This results in foaming, which effectively decreases the oil's viscosity and thus reduces the damping effect of the unit. While high-quality oil helps mitigate this issue to some extent, BC Racing takes it a step further by pressurising the dampers with nitrogen.

The nitrogen applies pressure on a floating piston, which in turn applies a constant pressure on the oil, significantly reducing aeration and thereby enhancing the consistency and quality of damping. The pressurised nitrogen also adds an additional aspect of effective spring rate to the damper unit.

Bearing Mounted Upper Spring Platform

Because the spring twists as it compresses, it's crucial to minimise stiction between the spring and its seats. Failure to relieve this tension can result in spring binding, where the spring rate effectively changes slightly as the spring compresses and extends. The tension generated can cause rapid deterioration of the spring perches and, in extreme cases, may lead to the loosening of the spring platform and locking collars. This loosening can cause the platform and locking collars to shift down the damper, resulting in uneven ride height and the risk of the spring dislocating during full damper extension.

The friction between the spring and seats also impacts steering effort, as the springs physically turn with the wheels. This introduces unnecessary friction into the steering system, which negatively affects the vehicle's handling characteristics.

BC Racing's bearing-mounted upper spring platform is one of their innovative designs. By significantly reducing stiction between the spring and its seats, BC Racing units avoid the aforementioned problems, thus improving the efficiency of the steering system and allowing the spring and damper to function as intended.

Optional Upgrades

Damper adjustment extenders – to spare you the hassle of removing the parcel shelf each time you need to adjust the damping on your BC Racing coilovers, we offer pairs of adjuster extenders. These affix to the adjuster knob on the top of the coilover and are available in three lengths: 110mm, 200mm, and 250mm. They attach swiftly with a straightforward grub screw design.

Assister spring perch – perhaps you prefer to incorporate some droop with your coilovers, or maybe you wish to adjust the ride by adding an additional, smaller assister spring. The spring perch and assister springs enable you to do just that. The springs are available in a broad range of spring rates.

Pillowball top mount – certain applications come with hardened rubber top mounts as standard to ensure the finest quality ride and keep costs as reasonable as possible for road use. However, we often provide a pillowball upgrade for these vehicles should you wish to eliminate this flex and make the car slightly more performance-oriented. Upgrading to pillowball eradicates the inherent flex present even in the hardened rubber used by BC Racing, thus enhancing the handling for those seeking the ultimate performance.