Grippy G8 GXP Upgrades

The Pontiac G8 GXP was unleashed from the factory with a 6.2 liter (396 ci) LS3 Corvette engine rated at 415 horsepower and coupled to a Tremec TR-6060 manual transmission for an impressive 0 to 60 in 4.5 seconds and 13 second quarter mile time. With this already impressive performance from the drivetrain, the first area that we decided to upgrade was the suspension package.

Why let the Aussies have all the fun when we could look to upgrade the already impressive stock Nurburgringer-tuned FE3 suspension package with a couple of extra goodies from Whiteline, Eibach Springs, Forgeline, and Nitto Tires? With this undertaking, we were looking to turn a good suspension into a great one with a few smooth moves of our own.

Why Modify?

With a respectable suspension under the car already, why would we want to play around with the existing suspension? Because handling characteristics and preferences are highly variable. They change from driver to driver based on driving style and driving environment. Straight from the factory, the suspensions are tuned for a broader range of street driving that encompasses driving styles from 16 year old gear grinders to 61 year old mid-life crisis drivers. For our road racing sedan, we wanted to fine tune it a bit more and bring out the beast in our “captive” import.

Bone stock from the factory, the G8 GPX already has a good suspension and fierce stance.

About Our Partners

Whiteline, our suspension experts on this project, are based in Minto, Australia, and have over forty years experience in manufacturing sway bars. Whiteline now carries a full line of suspension components in two different lines: Whiteline Flat Out and Whiteline Plus. 

Forgeline is one of the leading wheel companies making high end custom forged wheels in the performance industry. With wheels available in over 100 color and finish combinations, and from 17 to 22 inches, General Manager David Schardt helped us build a unique, stylish, and high performance wheel for our GXP.

Eibach is a family owned and operated company that began when Heinrich Eibach started producing springs in 1951. Today, Eibach manufactures springs for almost every application and type of driving. From F1 and Nascar racing to desert racing or street cruising, Eibach makes springs that help the performance and handling without breaking the bank.

Nitto Tire
is one of the most innovative performance tire companies in the aftermarket. With a wide range of offerings from street, to strip, to auto cross, Nitto makes a great performance tire for every vehicle and niche.

The Parts


Modifications started with the wheels and tires. Forgeline set us up with a set of their “S03P” Forged wheels, 3-piece, custom set up for the GXP with the correct widths: 19 x 10 (rear) and 19 x 9.5 (front). We had an almost unlimited choice of finishes, but we settled on Gloss Black wheel finish, with a Diamond Edge finish with a polished lip.

Tires from Nitto Tire were NT-05 tires, 275/35/19 and 245/40/19. The NT-05 tires are a maximum performance summer tire, very aggressive for the ultimate in handling.

Polyurethane bushings have been the bushing of choice for enthusiasts since their introduction into the marketplace in the 1970’s. They replace the soft rubber bushings and provide improved and predictable handling characteristics and have become an economically sound upgrade. Whiteline’s bushings are manufactured with a long-chain polymer compound with additional polyurethane constituents that allow for progressive resistance. The result is a bushing that is soft enough to handle low speed vibration and road noise yet still offers the abrasion and tear resistance of a harder urethane compound. Andrew Nolan, Product Manager at Whiteline Automotive in Comersby, Australia, explained, “That range of product is known as Whiteline Plus and delivers low speed ride quality and high speed chassis control.”

Features and Benefits

Key benefits of all WHITELINE PLUS polyurethane bushings include he ride quality of rubber bushings with the performance of solid links.

  • Long lasting durability.
  • Resistant to chemicals, oils, and weathering.
  • Enhanced handling, steering response, and road holding stability.
  • Increased braking capacities and positive brake pedal ‘feel’.
  • Wheel alignment rectification and optimization using offset and adjustable bushings and arms.

WHITELINE PLUS Individual Bushing Specifics

Whiteline Plus Spring Eye and Shackle Bushings provide more free pivot in spring length changes under bump and droop loading which enhances overall maneuverability of the vehicle. Adding the Whiteline Plus Shock Absorber Bushings helps to eliminate the shock valving lag at low speeds, even if the vehicle is equipped with heavy duty hydraulic or gas shocks. The Shock bushings enhance the performance of both new and used shocks by its density and linear flow properties which ultimately enhances the shock’s ability to cope with extreme bump and rebound travel.

Whiteline's strut bushing on the left compared to the stock strut upper bushing on the right.

Also available in the WHITELINE PLUS line is Steering Rack Bushings which help to promote stability of the steering rack and Trailing Arm Bushings that eliminate launch and driveline shudder under heavy loads. The bushing characteristics of the Trailing Arm Bushings allow for temporary pinion angle changes where a stiffer or softer bushing allows too much or too little flexibility causing premature tailshaft or gearbox failure.

WHITELINE PLUS Radius Rod/Caster Bar Bushings and Control Arm Bushings enhance handling characteristics by retaining the optimal suspension geometry. In addition to helping the vehicle perform with crisp response, these bushings optimize braking capabilities and provide better feel and stability.

Whiteline's 22mm X-Heavy Duty, adjustable sway bar installed on our project car.

Rear Swaybar. 22mm X-heavy duty, blade adjustable (BHR82XZ)

Designed to minimize body roll and spread cornering loads evenly across the tires, these swaybars provide more grip. The adjustability of the swaybar allows for tuning of the suspension without replacing the entire swaybar.

  • Allows for 3 points of adjustment.
  • Improves handling while minimizing body roll.
  • Allows for better tire grip which improves handling.

The slightly smaller, non-adjustable stock front sway bar (top) and Whiteline's 26mm X-Heavy duty, adjustable sway bar (bottom).

Front Swaybar. 26mm X-heavy duty, blade adjustable (BHF 62Z)

Providing a link between the left and right hand side of the suspension during cornering while minimizing the vehicle’s body roll, the 26mm swaybar ensures a more confident feel to the driver by improving tire grip on the road surface.

  • Allows for 4 points of adjustment.
  • Tunable for precise handling bias.
  • Manufactured with the finest grade spring steel.
  • Powder coated finish.

Whiteline's sway bar bushing being installed on the rear sway bar.

WHITELINE PLUS Sway Bar Bushings

  • Increase bar rates by 10-20%.
  • Reduce lag in the suspension as the bar moves.
  • Pivot at both mounting points, utilizing entire bar length.

According to Nolan, the Pontiac G8 has an “unpredictable oversteer characteristic” that is evident in all G8 vehicles. “The front 26mm adjustable sway bar counters the oversteer and provides four distinct stiffness settings allowing for precise handling adjustments. Cornering loads are spread more evenly across the tires delivering more grip, and that’s what it’s all about. You get improved tire wear as your tires stay flatter and more upright.” Nolan went on to say that nothing is sacrificed to achieve better handling. In fact, he stated, “Comfort improves because your car sits flatter through the bends meaning less movement inside the vehicle.”

Whiteline's front sway bar bushing.

Installing Whiteline sway bars and bushings improves the ride and driver comfort, promotes better tire wear, and provides more tire grip in the corners. Sounds like pretty good bang for the buck performance modification to us.

Other Upgrades

We had a couple more upgrades we wanted to make to our project car before we took it to the streets. We turned to the Whiteline Strut Brace for additional support up front and the Eibach Lowering Spring Kit to bring the roll center down. The addition of these two final upgrades would propel the handling to a superior level compared to a bland, sloppy handling that arrives off the showroom floor car. Looking forward to turning our muscular street performer into a real canyon carver, we eagerly began installing these final components.

Whiteline Strut Brace installed on our project car.

WhiteLine Strut Brace (KSB637)

Strut braces stiffen up the front end of the chassis and eliminate the chassis flex that takes place under heavy acceleration, deceleration, and hard cornering. If you like pushing your car harder through corners than the average driver, a strut brace is a must. Our good friends at Whiteline explained that their strut brace helps maintain alignment angles and spring rates; a difference that can be felt in sharper steering response. Featuring a lightwieght alloy construction, they are strong and look great on the car.

Whiteine's strut brace is a must for taking corners aggressively.

Eibach Pro Kit (38137.140)

According to our sources at Eibach, the Pro Kit for the G8 utilizes Eibach’s legendary coil spring system that improves performance and appearance simultaneously. The Pro Kit lowers the car’s center of gravity and reduces rear end squat during hard acceleration. Eibach’s published numbers on the ride height lowering is 1 inch in the front and 0.8 inch in the rear. Combining the Eibach Pro Kit with the Whiteline sway bars intensifies the ground hugging effect during cornering.

Eibach's lowering spring compared to the stock spring.

Installation

The installation for the Whiteline Sway Bars and Strut Brace with Eibach was pretty straight forward and took less than an afternoon to complete. We did find it easier to remove and install the front sway bar by unbolting and lifting the engine up a couple of inches using a two post lift and a hydraulic underhoist jack. If this option is not available, the sway bar can still be removed by loosening the steering rack and power steering lines.

Tips on Whiteline Sway Bar Installation:

  • Installation should be done at ride height. If this is not an option, the bolts should be tightened at ride height to avoid preloading the sway bar.
  • Apply polyurethane grease to the contact surfaces of the new polyurethane bushings.
  • When setting the adjustments on the adjustable sway bar, always start with a softer setting then adjust to a harder setting if needed.
  • Use caution to not over tighten the sway bar pin links. The nuts should be tightened until the washer and bushings stop rotating, then turn 2/3 rds of a turn tighter.
  • Check all fasteners after 50-60 miles of road time. This gives the components a chance to “settle-in”.

Eibach's progressive lowering spring.

Eibach Pro Kit Lowering Spring Installation

Strut springs should only be replaced by a technician with experience in changing strut springs, and only the proper tools to perform the task should be used. Springs are under pressure and can cause serious injury if the proper precautions are not taken.

Changing strut springs using spring compression tools.

Eibach Springs Installation Tips:

  1. Measure vehicle’s ride height before starting installation and then again after installation. This will tell you how much the vehicle has been lowered.
  2. Measure from the top of the wheel rim to the highest point on the fender well. After driving the car for 10-15 miles, remeasure the height to check for settling of the springs and spacers.
  3. Before removing the strut assembly, label each part from top to bottom in sequential numbers. This will ensure that you will reassemble the parts in the correct order.
  4. Draw a vertical line with a marker across all the components. This helps re-installation of the OE parts in the original orientation.
  5. Mark the position of all alignment-related bolts. This will give you a decent starting point to work from in the post installation alignment.
  6. Work from one corner of the vehicle at a time. If you get confused during re-assembly, you can refer to the corresponding assembly for reference.
  7. Re-install all fasteners in the same orientation as they were removed.
  8. Use spring compressors when removing springs from your car or from the strut assembly.
  9. Note the orientation of the OE springs and install the Eibach springs the same way in the spring seat.
  10. Re-torque mounting bolts after 500 miles.

Finishing the Job

With all the parts installed, we rolled our G8 out of the garage and asked the car owner to drive it for 20-30 minutes. With instructions to drive it hard to “seat the components”, we sent our driver out into the world. Before the installation, the driver complained that the “car feels solid but the rear end is slightly loose. There is a lot of body lean when you turn sharply, and during braking there is substantial nose dive.”

We felt confident that the driver would return with detailed analysis of the changes and, as luck would have it, as we were finishing up the shop clean up, our driver returned with a big smile on his face. When asked about the handling, our driver candidly explained that “the car stays much flatter during rapid quick steer movements, it has much quicker turn in, and the oversteer is gone.

The rear of the car feels very comfortable in hard turns”. His overall assessment of the new suspension changes were summed up with, “I love the looks with the lowering of the car, the easy ride, the firmer but certainly livable handling, and my confidence has improved big time. Now I feel like a true serious sport-touring driver.”

Article Sources

About the author

Tom Bobolts

Tom started working for Power Automedia in early 2008 at the young age of 20. Starting off as an intern spinning wrenches in the PowerTV garage, Tom cut his teeth helping us build the very project cars we feature. Since moving inside the office, most of his time is spent writing and shooting installs - but he still finds time to get out in the shop. Outside of work, Tom enjoys a variety of different motorsports from Street Bikes, Muscle Cars and just about anything that demands high amounts of horsepower.
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