BC Racing ER Series Coilovers for 2001-2005 Honda Civic FWD (EM2/ES1)
BC Racing ER Series Coilovers for 2017+ Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
BC Racing ER Series Coilovers for 2017+ Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
BC Racing ER Series Coilovers for 2017+ Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
BC Racing ER Series Coilovers for 2017+ Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
BC Racing ER Series Coilovers for 2017+ Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut

BC Racing

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SKU: S-28-ER

BC Racing ER Series Coilovers for 2017+ Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut

Sale price$1,935.00Regular price $2,230.00
Out of Stock (about 4-6 weeks)

Fitment Notes

All suspension is designed to lower the vehicle. Factory ride height cannot be achieved for most applications.

All BC Racing suspension fits 2WD vehicles unless specified AWD. Notes regarding electronic damping (EDC, DDS, etc.) pertain to physical fitment only.

BC Racing coilovers DO NOT interface w/ OEM electronic damping control systems. Additional parts may be needed to remove error codes if electronics exist with the OEM suspension.

Pillowball Mounts do not mean Camber Plates. Pillowball refers to the type of bushing.

Product images may not represent the actual SKU.

Handling Time

In-Stock: 1-3 business days
Products that are in-stock and do not require customization usually ship the same business day if ordered before 2pm ET. Orders placed after 2pm ET will ship the following business day. 

Out of Stock: 3-5 weeks
Products that are out of stock have an average lead time of 3-5 weeks.

Custom Builds: 3-5 weeks
Custom builds vary in time based on the options selected and available parts. Custom builds include any combination of the following options.

  • Extreme Low
  • DS/ER/RM/HM/ZR/ZX Series
  • Custom Spring Rates
  • Swift Springs
  • Top Mounts

Out of Stock (Swift Springs): 1-3 months
If Swift Springs are out of stock, the wait time can be about 1-3 months. Please ask for an ETA prior to ordering.

Returns

Orders can be returned within 30 days of fulfillment if all rules shown below are met.

  • Products must be in original packaging and in a new and resalable condition.
  • Any product that was used or fully/partially installed is non-returnable.
  • Custom products, special order products, and services are non-returnable and non-refundable.
  • Shipping fees and tax are non-refundable.
  • If the return of an item was caused by an error on our part, or a manufacturer's part, we will cover the shipping fees.

More Details

2-Year Warranty

BC Racing North America offers a two-year warranty against manufacturing defects. All warranty claims must be submitted directly to BC Racing North America.

More Details

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 A4/S4 B9 chassis and refined until it balances ride quality with performance — the reason A4/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 A4/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 2017+ Audi A4/S4 FWD/AWD (B9) 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
  • Designed for 48.5mm front strut diameter — measure yours before ordering.
  • The ER Series is not available in Extreme-Low configuration.
Vehicle Fitment
  • 2017 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2018 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2019 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2020 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2021 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2022 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2023 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2024 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2025 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut
  • 2026 Audi A4/S4 FWD/AWD (B9) 48.5mm Front Strut

Reviews / Q&A

FAQs

Please read our FAQs page to find out more.

How much will BC Coilovers lower my car?

On average, Standard Drop allows about 1-2 inches of drop range below factory ride height. Extreme Low allows about 2-3 inches of drop.

Can BC Coilovers achieve factory ride height?

No. In most cases, factory ride height cannot be achieved.

What is a custom build vs off-the-shelf kit?

The stock level displayed on our website reflects the availability of standard “off-the-shelf” kits, unless noted otherwise in the product description. Selecting any custom options—such as Extreme Low, custom spring rates, Swift Spring upgrades, or top mount changes—will result in a custom-built kit. Please note: all series except the BR Series are built to order, with the exception of select popular DS Series kits that may be in stock. Also, some popular Extreme Low kits are in stock as well. To identify these, look for "Extreme Low" in the product title.

Will the struts be valved correctly?

Yes! The shocks and/or struts are always valved to match the spring rates you choose during a custom build. There is no additional cost.

Can they be rebuilt?

Yes, all BC Racing Coilovers can be rebuilt by purchasing individual replacement parts. For example, if a strut leaks, you can simply replace the shock cartridge.

Is there rush shipping available?

Rush shipping is not offered, but all in-stock kits ship very fast— most by the next day.

Customizing the coilovers in any way will delay the shipment by a few weeks on average.

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