Whether you're chasing lap times, refining your daily drive, or simply dialling in your stance, BC Racing coilovers offer a range of options to suit every kind of motoring enthusiast. But with multiple series available - BR, DS, ER and more, it can be tricky to know which setup is right for your car and your goals.
Let’s break down the key differences between the BC Racing coilover series, what’s adjustable, and how to make sense of spring rates
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BC Racing Coilover Series Explained
BC Racing coilovers are split into several distinct series, each designed with specific performance goals in mind. Here’s what sets them apart:
BR Series – Street & Track All-Rounder
- The most popular and versatile option.
- Ideal for daily driving, spirited road use, and occasional track days.
Features:
- Mono-tube damper design.
- 30 levels of damping adjustment (combined bump and rebound).
- Ride height adjustable via the shock body (not spring preload).
- Perfect for: Drivers who want improved handling without sacrificing comfort.
RM Series – Inverted for Strength
- Similar to BR, but with an inverted damper design.
- Inverted struts offer increased strength and heat dissipation - ideal for heavier loads and aggressive driving.
Features:
- Inverted mono-tube design (especially beneficial for MacPherson setups).
- 30-way damping adjustment.
- Perfect for: Track-focused builds or vehicles with high cornering loads.
DS Series – Digressive Damping
- Designed for sharper response and better control at high speeds.
- Digressive valving offers firm low-speed damping with softer high-speed response meaning they're great for track use.
Features:
- Digressive piston design.
- 30-way damping adjustment.
- Perfect for: Drivers who want precise feedback and control during aggressive driving.
ER Series – External Reservoir Performance
- A step up in performance with separate bump and rebound adjustment.
- External reservoirs improve oil capacity and cooling, reducing fade during extended track sessions.
Features:
- Mono-tube with external reservoir.
- Independent bump and rebound adjustment.
- Perfect for: Serious track enthusiasts and competitive motorsport use.
HM Series – Inverted with External Reservoir
- Combines the inverted design of the RM Series with the external reservoir of the ER Series.
- Offers maximum strength and heat resistance with advanced damping control.
Features:
- Inverted mono-tube with external reservoir.
- Independent bump and rebound adjustment.
- Perfect for: High-performance builds needing durability and fine-tuned damping.
ZR Series – 3-Way Adjustable Race Spec
- Race-grade coilovers with three-way damping adjustment: high-speed bump, low-speed bump, and rebound.
- Designed for professional motorsport applications.
Features:
- External reservoirs.
- 3-way damping adjustment.
- Perfect for: Competitive racing teams and advanced track setups.
ZX Series – 4-Way Adjustable Elite Spec
- The pinnacle of BC Racing’s coilover technology.
- Offers four-way adjustment for ultimate control: high-speed bump, low-speed bump, high-speed rebound, and low-speed rebound.
Features:
- External reservoirs.
- 4-way damping adjustment.
- Perfect for: Elite motorsport applications where every millisecond counts.
Spring Rates – What Does 5/6kg.mm Actually Mean?
When browsing coilovers, you’ll often see spring rates listed like “5/6kg.mm”. This refers to the stiffness of the springs:
- 5kg/mm means the spring requires 5 kilograms of force to compress it by 1 millimetre.
- 6kg/mm is slightly stiffer, requiring 6 kilograms per millimetre.
The first number usually refers to the front springs, and the second to the rear.
Your ideal spring rate depends on your car’s weight, intended use, and personal preference:
Softer Springs (e.g. 4/5kg.mm):
- More comfortable ride.
- Better for daily driving and uneven road surfaces.
- Allows more body roll, less ideal for aggressive cornering.
Stiffer Springs (e.g. 8/10kg.mm):
- Sharper handling and reduced body movement.
- Better for track use and high-speed stability.
- Can feel harsh on the road, not ideal for comfort.
BC Racing can supply coilovers with custom spring rates where required. Please contact JXL Performance to discuss and arrange this.
Final Thoughts
BC Racing coilovers offer a wide spectrum of performance, from street-friendly comfort to full-blown race spec. Understanding the differences between each series. and how spring rates affect your ride will help you make an informed decision that suits your driving style and goals.
Still unsure which series is right for you? Drop us a message, we’re happy to help you spec the perfect setup.