Product Details
BC Racing ER Series Coilovers for the 2017+ Audi A4/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 B9 chassis and refined until it balances ride quality with performance — the reason A4/S4 (48.5mm Front Strut) 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 A4/S4 (48.5mm Front Strut) 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 | 2017+ Audi A4/S4 (48.5mm Front Strut) |
| Drivetrain | FWD/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 |
| Suspension Design - Front | True Coilover |
| Suspension Design - Rear | True Coilover |
| Notes |
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Vehicle Fitment
- 2017 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2018 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2019 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2020 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2021 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2022 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2023 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2024 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2025 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)
- 2026 Audi A4/S4 (48.5mm Front Strut) FWD/AWD (B9)