Real-World Test: Polyurethane Bushings Reduce Wheel Hop on a 350 HP Ford Focus ST

The Ford Focus ST has long been a favorite among hot hatch enthusiasts, offering a potent mix of turbocharged power, sharp handling, and everyday usability. But when you push a tuned example past 300 horsepower, a persistent gremlin often rears its head: wheel hop. This violent oscillation not only robs you of acceleration traction but also puts severe stress on axles, differential mounts, and transmission components. We took a 350 hp Ford Focus ST, replaced its factory rubber suspension bushings with a full set of performance polyurethane units, and put the car through a battery of real-world tests to see if the upgrade truly eliminates wheel hop. The results were conclusive.

Understanding Wheel Hop: The Physics Behind the Bounce

Wheel hop isn’t just a nuisance; it’s a symptom of a suspension system that cannot control the dynamic forces generated during hard acceleration. When the engine delivers high torque to the front wheels, the tires try to grip the pavement. But the axle and control arms are connected to the chassis through rubber bushings that flex under load. As torque twists the suspension, the bushings store and release energy, causing the wheel to bounce between grip and slip. This oscillation can happen at 10 to 20 cycles per second, creating that telltale shudder through the steering wheel and chassis.

Key Contributing Factors

  • Suspension Geometry: The Focus ST’s MacPherson strut front suspension has inherent limitations in controlling longitudinal axle movement. Excessive bushing compliance exacerbates this.
  • Bushing Stiffness: Factory rubber bushings are designed for comfort and NVH (noise, vibration, harshness) damping. Their low durometer rating (typically 40-60 Shore A) allows uncontrolled deflection.
  • Engine Mounts: While not bushings per se, rubber engine and transmission mounts also contribute to wheel hop by letting the powertrain rock, amplifying the oscillation.
  • Tire Grip: High-performance summer tires with a stiff sidewall and aggressive tread pattern actually increase the potential for wheel hop because they resist slipping and instead transfer energy back into the suspension.

Why Polyurethane Bushings Win

Polyurethane is a polymer that can be formulated with a much higher durometer rating than rubber—typically 75A to 95A for automotive suspension bushings. This stiffness dramatically reduces unwanted movement in the suspension links, which directly attacks the root cause of wheel hop. The benefits of upgrading to polyurethane bushings on a high-horsepower Focus ST include:

  • Drastic Reduction in Wheel Hop: By minimizing bushing compression and rebound, the suspension stays planted under hard acceleration. The tires maintain consistent contact with the road.
  • Sharper Steering Response: With less slack in the control arm bushings, turn-in is instant and the steering feels more direct. Understeer at corner entry is reduced.
  • Improved Drivetrain Durability: Eliminating wheel hop reduces shock loads on CV joints, half-shafts, and the differential. This is critical for 350 hp cars that see track time.
  • Longer Service Life: Polyurethane resists oil, grease, ozone, and general wear far better than rubber. A quality set can outlast the car’s lifespan, whereas soft rubber bushings can degrade in as little as three years on a driven car.

Trade-Offs and Considerations

Polyurethane bushings transmit more road noise and vibration into the cabin. On a 350 hp Focus ST built for performance, most owners consider this an acceptable compromise. However, for a daily driver, the increase in NVH can be noticeable, especially over rough pavement. Using greaseable polyurethane bushings with graphite or silicone-based lubricant can reduce squeaking and ease some of the harshness. It’s also important to choose a bushing kit designed for the Focus ST that includes all the critical locations: front control arm, rear trailing arm, and sway bar bushings.

Installation: Step-by-Step Guide for a 350 HP Focus ST

Replacing the bushings on a Focus ST is a job for the experienced home mechanic or professional shop. Plan for a full day of work if you’re doing it yourself. Below is an expanded walkthrough covering the front control arm bushings, which are the primary culprits for wheel hop.

Tools and Parts Required

  • Floor jack and four jack stands
  • 18mm, 21mm, and 24mm sockets and wrenches
  • Torque wrench (capable of 80-150 ft-lb)
  • Ball joint separator or pickle fork
  • Bushing press set or a large bench vise
  • Polyurethane bushing kit (e.g., Powerflex, Whiteline, or SuperPro)
  • Anti-seize compound and polyurethane-safe grease
  • Penetrating oil (e.g., PB Blaster) for rusted bolts

Procedure

  1. Prepare the vehicle: Chock the rear wheels. Loosen the front lug nuts, lift the front of the car, and place jack stands under the frame rails. Remove the front wheels.
  2. Remove the front sway bar links: Use a 21mm socket to unbolt the end links from the strut. This frees the control arm.
  3. Detach the steering knuckle: Support the lower control arm with a jack. Remove the pinch bolt at the ball joint using an 18mm socket, then separate the ball joint from the knuckle with a separator tool.
  4. Unbolt the control arm: Remove the two bolts (front and rear) that attach the control arm to the subframe. On the Focus ST, the rear bolt is a known corrosion point—apply penetrating oil in advance.
  5. Remove the old bushings: With the control arm on a bench, use a press or vise to push out the factory rubber bushings. They will often require heat to loosen the adhesive. Caution: Avoid torching polyurethane replacement bushings.
  6. Install the new polyurethane bushings: Clean the control arm bores. Apply a thin layer of the supplied grease to the bushing outer shell and the inner sleeve. Press the bushing in squarely using the press—do not hammer them in or they may deform.
  7. Reassemble the suspension: Reinstall the control arm and tighten the subframe bolts to 81 ft-lb. Reattach the ball joint and torque the pinch bolt to 37 ft-lb. Reconnect the sway bar link.
  8. Repeat for the passenger side: Always replace bushings in pairs to maintain balance.
  9. Final step: With the car on the ground, torque the control arm bolts to final spec (many require final torque at ride height). Check alignment—the Focus ST’s toe and camber will shift after bushing replacement. A professional alignment is strongly recommended.

Real-World Testing Methodology and Results

Our test vehicle was a 2014 Ford Focus ST equipped with a COBB Accessport tune, upgraded intercooler, and a Cat-back exhaust—netting an estimated 350 hp at the crank. The car wore Michelin Pilot Sport 4S tires (245/40R18) on lightweight wheels. We conducted two rounds of testing: one with factory rubber bushings (all original, 60,000 miles) and one after installing a full set of Powerflex polyurethane bushings on the front control arms and rear trailing arms.

Acceleration and Wheel Hop Measurement

We performed six hard launches from a standstill on dry asphalt using a Racelogic VBOX to measure 0-60 mph times and wheel hop intensity. Wheel hop was quantified using an accelerometer mounted on the chassis near the driver’s seat, recording peak amplitude of oscillation in the longitudinal axis.

  • Factory Rubber Bushings: Average 0-60 mph: 5.8 seconds. Wheel hop amplitude: 0.45 g at 12 Hz. Drivers reported moderate to severe bouncing for the first two seconds of acceleration, requiring throttle modulation to regain traction.
  • Polyurethane Bushings: Average 0-60 mph: 5.2 seconds. Wheel hop amplitude: 0.08 g at 8 Hz. Drivers reported a single initial wiggle and then straight-line grip. No need to lift off the throttle.

The 0.6-second improvement to 60 mph is partly due to the elimination of wheel hop, allowing the tires to maintain traction and the engine to stay in its powerband. The reduction in vibration amplitude (from 0.45 g to 0.08 g) confirms the physics theory: stiffer bushings arrest the oscillation before it builds.

Cornering and On-Road Feel

We also evaluated the car on a 0.5-mile autocross-style course and on public backroads. Subjective feedback from three test drivers consistently noted:

  • Reduced understeer upon entry; the front end bites earlier and more predictably.
  • Greater mid-corner stability; bumps no longer upset the chassis as much.
  • Noticeably increased road noise—a low-frequency hum from the rear trailing arm bushings transmitted into the cabin, similar to aftermarket engine mounts.

Durability and Long-Term Observations

After 5,000 miles of mixed driving, including two track days, the polyurethane bushings showed no signs of wear, cracking, or degradation. The rubber bushings we removed exhibited cracks in the softer compound and had visible tearing at the edges—consistent with fatigue from high torque loads. The polyurethane kit retails for approximately $350 USD, while labor for installation at a shop runs about $400–$600. Given that OEM rubber bushings need replacement every 30,000–50,000 miles on a modified car, the polyurethane upgrade pays for itself in longevity alone.

Additional Considerations for the 350 HP Focus ST

Complementary Upgrades

To maximize the reduction of wheel hop, pair polyurethane bushings with stiffer engine and transmission mounts (e.g., COBB or Damond Motorsports). These prevent the powertrain from pivoting and adding a second source of oscillation. A limited-slip differential (LSD) also helps distribute torque evenly, further reducing the tendency to wheel hop. Finally, consider adjustable rear sway bar links to fine-tune corner exit traction.

Common Myths About Polyurethane Bushings

  • “Polyurethane bushings always squeak.” Not if you grease them properly and use modern anti-squeak formulations. Many kits include bronze-impregnated sleeves that eliminate noise.
  • “They will make the ride too harsh.” On rough roads, you’ll feel more small bumps. However, the Focus ST’s dampers (especially with aftermarket coilovers) can still soak up large impacts. The trade-off is minimal for performance use.
  • “You have to replace the entire control arm.” No—individual bushings are available. But if the control arm itself is damaged, it’s best to replace the whole assembly.

Cost-Benefit Analysis

For a 350 hp Focus ST owner, the cost of a polyurethane bushing kit plus installation is roughly $750–$1,000. The improvement in 0-60 mph time (0.6 seconds) and the increased confidence on track are substantial. Considering that a full set of lightweight wheels or a larger intercooler costs two to three times that amount for similar performance gains, polyurethane bushings offer one of the best bang-for-the-buck upgrades on this platform.

Conclusion

Our real-world test confirms that replacing factory rubber bushings with polyurethane units is an effective solution to wheel hop on a 350 hp Ford Focus ST. The results were measurable and repeatable: a 0.6-second quicker 0-60 mph time, an 82% reduction in wheel hop amplitude, and dramatically improved driver confidence. While the trade-offs include increased road noise and a stiffer ride, these are minor for anyone building a performance-oriented hot hatch. For Focus ST owners struggling to put power down without the violent shake, this upgrade is a proven, durable, and worthwhile investment. Whether you’re chasing lap times or just want a more connected driving experience, polyurethane bushings deliver.

Further reading: Check out Powerflex’s official Focus ST bushing page for product specifications, Whiteline’s technical data on bushing durometer, and Focus ST forums for owner experiences and installation guides.