The Audi B9 S4 has earned a strong following among performance sedan enthusiasts for its balanced blend of everyday utility and serious power. With a turbocharged V6, sophisticated all-wheel drive, and a chassis tuned for both comfort and agility, the B9 S4 delivers a driving experience that rivals more expensive German machinery. But for those looking to sharpen its character further, suspension and wheel upgrades are among the most impactful modifications. This article offers a comprehensive power comparison between a stock B9 S4 and one fitted with Vossen wheels and H&R springs, digging beyond simple numbers to explore how these changes affect real-world performance.

The Stock B9 S4: A Benchmark in Performance Sedans

The B9 generation S4 arrived with a 3.0-liter turbocharged V6 (EA839) producing 349 horsepower and 369 lb-ft of torque. This engine uses a single twin-scroll turbocharger, direct injection, and Audi’s latest Quattro system with a rear-biased torque split. The standard 8-speed Tiptronic automatic transmission provides quick shifts, and the car can accelerate from 0–60 mph in 4.4 seconds according to factory tests. Independent tests have recorded times as low as 4.2 seconds with proper launch control, and the quarter-mile is typically covered in 12.5–12.7 seconds at around 111 mph.

Suspension and Handling from the Factory

The stock suspension uses a five-link front and rear setup with coil springs and passive dampers. Optional adaptive dampers (Audi Magnetic Ride) are available, improving ride quality and body control. Steering is electromechanical with progressive ratio, offering good feedback for a modern sedan. Skidpad numbers hover around 0.92g, and braking from 60 mph is accomplished in about 110 feet. While these figures are impressive, the stock ride height and wheel design prioritize comfort and stability over outright cornering precision. The 19-inch wheels (optional 20-inch) carry a fair amount of unsprung mass, and the sidewall flexibility of the rubber contributes to some understeer at the limit.

Key Performance Metrics (Stock)

  • Engine: 3.0L turbo V6 (349 hp / 369 lb-ft)
  • 0–60 mph: 4.4 seconds (factory), ~4.2 seconds (independent)
  • Quarter-mile: 12.5–12.7 seconds @ 111 mph
  • Top speed: Electronically limited to 155 mph
  • Lateral acceleration: ~0.92g
  • Braking 60–0 mph: ~110 feet

For more official specifications, refer to Audi’s S4 overview page.

Why Vossen Wheels and H&R Springs?

Wheels and springs are among the most common aftermarket upgrades for the B9 S4, and the combination of Vossen wheels and H&R springs is a proven pairing. Vossen offers lightweight forged and flow-formed wheels with aggressive offsets and modern designs, while H&R is a leading manufacturer of high-performance sport springs that lower the vehicle while maintaining proper suspension geometry. Together, they can transform both the appearance and the dynamics of the S4.

Vossen Wheels: Weight Reduction and Stance

Vossen’s lineup for the B9 S4 includes models like the Vossen HF-5 and Vossen ML-8101, typically in 20×9 or 20×10 sizes. The company uses advanced flow-forming technology to reduce weight without sacrificing strength. A set of 20-inch Vossen wheels can save 8–12 pounds per corner compared to the stock 19-inch wheels. This reduction in unsprung weight has measurable effects:

  • Improved acceleration – less rotational inertia means the engine can rev more freely. While the peak horsepower remains unchanged, the car feels quicker in gear.
  • Better braking – reduced unsprung mass allows the suspension to keep the tire in better contact, shortening stopping distances.
  • Sharper steering response – lighter wheels allow the steering rack to react more quickly to inputs.

Additionally, the wider track (by 0.5–1.0 inch per side) improves lateral stability and cornering grip. Vossen’s S4 fitment guide provides detailed sizing and offset recommendations.

H&R Sport Springs: Lower Center of Gravity, Better Geometry

H&R’s sport springs lower the B9 S4 by approximately 1.0–1.4 inches (depending on configuration). This reduction in ride height directly lowers the center of gravity, which reduces body roll during cornering and improves transitional response. The springs themselves have a progressive rate, meaning they offer a compliant ride over small bumps but stiffen up under compression during hard cornering or braking.

Key benefits include:

  • Reduced body roll – less lateral weight transfer allows the chassis to use the tire contact patch more effectively.
  • Improved camber curves – a slight drop improves static negative camber, helping the front tires maintain grip under cornering loads.
  • Lowered stance – the gap between tire and fender is minimized, giving the S4 a more aggressive and purposeful appearance.

H&R recommends pairing their springs with upgraded shock absorbers (such as Bilstein or KW) for optimal damping, but many owners use them with the stock dampers for a cost‑effective upgrade. H&R’s application page for Audi S4 B9 lists the exact part numbers.

Power Comparison: Measured vs. Felt Differences

Strictly speaking, neither Vossen wheels nor H&R springs increase engine power output. The car still produces 349 hp and 369 lb-ft at the crank. However, the perception of performance and actual tractive ability can change significantly. The following areas show the most tangible improvements:

Acceleration and Throttle Response

The reduction in rotational inertia from lighter wheels—especially when paired with a more aggressive tire (like Michelin Pilot Sport 4S or Continental ExtremeContact Sport)—can improve 0–60 times by 0.1–0.2 seconds in real-world testing. More importantly, the car feels more eager to rev during roll-on acceleration (30–70 mph passes). Combined with the reduced weight, the effective power-to-weight ratio improves marginally. Since the stock B9 S4 weighs about 3,900 pounds, saving 30–40 pounds of unsprung mass helps the drivetrain deliver power more effectively.

Cornering and Grip

The suspension upgrades have a more pronounced effect on cornering performance. With H&R springs, the B9 S4 typically sees an increase in lateral grip of 0.02–0.04g, moving toward 0.95–0.96g on a skidpad. The front end is more willing to rotate, reducing understeer. On track or autocross, this translates to quicker lap times—often 1–2 seconds per 60‑second lap compared to stock.

Braking Consistency

While the stock brakes are strong, lowering the car reduces forward weight transfer under braking. Combined with the lower unsprung mass, the car stops more confidently and with less front‑end dive. Stopping distances from 60 mph can shorten by 2–4 feet.

Dyno Results: What to Expect

If the car were run on a chassis dynamometer, the stock engine would produce roughly 310–320 whp (depending on drivetrain losses). With lighter wheels, there is a small reduction in driveline loss because the rotational inertia is lower, but the difference is typically within the margin of error. The real gain is not in peak numbers but in how the power is delivered to the pavement. For those seeking a genuine horsepower increase, a stage 1 ECU tune (e.g., APR, Unitronic) can raise output to around 420–440 hp, and the wheel and spring mods then become even more effective at translating that power into acceleration.

Driving Experience: Objective Data and Subjective Feedback

Numbers only tell part of the story. Enthusiasts who have made this combination report a transformed driving character:

  • Steering feel – The reduction in unsprung mass and lower ride height give the steering more weight and feedback. The on‑center feel improves, and the car tracks straighter under acceleration.
  • Ride quality – With the progressive‑rate H&R springs, the ride is firmer but not harsh over most pavement. Sharp impacts like potholes are more noticeable, but general road compliance remains good. Many owners find the trade‑off acceptable for the handling gains.
  • Body control – The car no longer wallows during high‑speed lane changes or sweeping corners. It feels planted and confident, especially on undulating roads.
  • Visual appeal – A lowered S4 with concave Vossen wheels and a proper tire fitment draws admiring glances. The stance becomes aggressive without being overly slammed.

"I was initially skeptical about spending money on wheels and springs without adding power, but after a few drives I realized the car feels like a different machine. It rotates into corners more willingly, and the steering is much more communicative. It's the best suspension mod I've done." – B9 S4 owner on AudiWorld

Potential Compromises

No modification is perfect. The stiffer springs can cause the car to tramline on grooved highways, and the lower stance may scrape on steep driveways or speed bumps. The ride is noticeably firmer, so those who prioritize long‑distance comfort may want to keep the factory adaptive dampers. Additionally, the wider wheels may poke beyond the fenders slightly (depending on offset), leading to potential rock chip issues if not properly fitted. Using a quality alignment—with a slight increase in rear toe and front negative camber—can mitigate uneven tire wear.

Comparison with Other Performance Mods

Wheels and springs are often the first stage in a broader build. For the B9 S4, common subsequent upgrades include:

  • Downpipe and exhaust – frees up some horsepower and improves sound.
  • Intercooler – helps maintain power on hot laps.
  • Turbo inlet and blow‑off valve – minor gains with better boost response.
  • Engine tune – as mentioned, 70–90 hp gains are typical.

The beauty of the Vossen + H&R setup is that it complements any future powertrain upgrades. A tuned engine with 430+ hp will be more usable if the chassis and suspension are optimized to handle it. Conversely, adding a tune to a car with stock wheels and springs would likely result in more traction issues and heavier body roll.

Conclusion: Is the Vossen & H&R Upgrade Worth It?

For the B9 S4 owner seeking a more engaging driving experience without sacrificing daily usability, the combination of Vossen wheels and H&R springs delivers measurable improvements in cornering grip, braking stability, and steering feel. While peak engine power remains unchanged, the car’s ability to transfer that power to the road is enhanced. The aesthetic transformation is also a major benefit. When compared to the stock configuration, the modified car feels lighter, more responsive, and more planted. It is a confident step toward unlocking the full potential of the B9 S4 chassis.

For those who plan to continue modifying, this setup lays a solid foundation. For those who want immediate, daily‑enjoyable upgrades without extreme cost or compromise, it is one of the most satisfying investments available.

External references: Audi S4 official specs · Vossen wheel fitments for B9 S4 · H&R spring applications for Audi S4 · AudiWorld B9 S4 forum discussions