Product Details
BC Racing ER Series Coilovers for the 2018-2024 Audi S4 (B9) put race-grade adjustability in reach of the serious track-day driver, with independent compression and rebound tuning at every corner. Every kit is extensively tested on the S4 B9 chassis and refined until it balances ride quality with performance, the reason S4 coilovers from BC Racing are the best-selling adjustable kits in their segment worldwide.
ER Series kits run a linear twin-piston design in a mono-tube body, with compression and rebound on separate external adjusters. That lets you fine-tune chassis balance corner by corner, stiffer front for turn-in, softer rear for exit grip, whatever the session calls for. The off-the-shelf setup from BC Racing is deliberately balanced, spring rates and valving chosen so the kit feels comfortable day-to-day without giving up performance when you push it. Drivers who want a different recipe can spec Swift Springs, custom spring rates, or fully custom valving at checkout; BC will tune the dampers to match, which is a depth of customization most brands only offer on their top-tier kits.
Since 2004, BC Racing has grown into one of the most trusted names in aftermarket coilovers, not by racing to the bottom on price, but by pairing that price with real build quality, deep customization options, and a damper design any suspension shop can rebuild instead of replacing. These S4 coilovers arrive tuned for the B9 chassis and ready to bolt in, no break-in period, no guessing at setup. Every kit ships with a 2-year manufacturer warranty, lifetime access to BC service parts (pistons, seals, shafts, no unit replacement required when it's time for a rebuild), and in-house tech support from both BC Racing and the Springrates team.
Features
- 30-level rebound adjustment (top of damper)
- 30-level compression adjustment (external reservoir)
- Mono-tube damper with linear twin-piston design
- Ride height adjustable independent of spring preload
- Upper mount hardware varies by chassis, camber plates, pillowball, or reused OEM mounts. See the Specifications table for what's included on your kit.
- Swift Spring and custom spring rate upgrades available at checkout
- Custom damper valving paired with custom spring rates on request
- Fully rebuildable, replacement parts available from BC for the life of the shock
- 2-year manufacturer warranty against defects
Specifications
| Part Number | S-28-ER |
| Part Name | ER Series Coilovers |
| Vehicle | 2018-2024 Audi S4 |
| Drivetrain | AWD |
| Chassis Code | B9 |
| Damping Adjustment | 2-Way (30 levels rebound/30 levels compression) |
| Ride-Height Adjustable | Yes |
| Spring Rate - Front | 10 kg/mm |
| Spring Rate - Rear | 8 kg/mm |
| Spring Size - Front | 62-220-10K |
| Spring Size - Rear | 62-190-8K |
| Swift Springs - Front | 62-203-X |
| Swift Springs - Rear | 62-178-X |
| Camber Plates - Front | Not Applicable |
| Camber Plates - Rear | Not Applicable |
| Rear Damping Extenders | Not Compatible |
| Suspension Design - Front | True Coilover |
| Suspension Design - Rear | Divorced |
| Notes |
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Vehicle Fitment
- 2018 Audi S4 AWD (B9) 48.5mm Front Strut
- 2019 Audi S4 AWD (B9) 48.5mm Front Strut
- 2020 Audi S4 AWD (B9) 48.5mm Front Strut
- 2021 Audi S4 AWD (B9) 48.5mm Front Strut
- 2022 Audi S4 AWD (B9) 48.5mm Front Strut
- 2023 Audi S4 AWD (B9) 48.5mm Front Strut
- 2024 Audi S4 AWD (B9) 48.5mm Front Strut