At first blush, one wouldn’t guess that our recently-purchased 1999 Pontiac Firebird Trans Am with the optional WS6 Ram Air and Handling Package has nearly 100,000 miles on its odometer. It was a two-owner vehicle we found on local used-car lot that had been purchased at a dealer auction. The undercarriage cleanliness suggested it hadn’t seen the salty roads associated with Nebraska winters, and the overall condition of its exterior and interior says it was well cared for by a proud owner.
So many Firebirds and Camaros of this era have been modified over the years. The addition of aftermarket intake and exhaust components, larger wheel and tire packages, high-end audio equipment, and suspension upgrades is commonplace. Not a single component had ever been replaced or modified on this Trans Am beyond the warranty repairs and general maintenance performed by the local GM dealer. The LS1 V-8 under hood runs exceptionally well and its 4L60E automatic transmission operates as it should
Despite its originality and excellent operational condition, our Trans Am was due for a bit of routine maintenance. Its brakes pulsated during application at higher speeds, and the suspension wasn’t as taut as expected. A thorough inspection revealed nothing more than the need for new brakes and shocks. Since the two required a similar level of disassembly, particularly in the front suspension, it only made sense that we tackle both concurrently. Follow along as we accomplish that task without compromising the factory appearance.
Fourth-gen Firebird Basics
GM’s fourth-generation F-car was the most refined version ever produced when introduced in 1993. Its thick front and rear sway bars, short-and-long arm (or SLA) front suspension, and positively-located rear axle provided excellent ride and handling qualities. And it proved the perfect platform for future enhancements. In 1996, Pontiac released its WS6 package, which combined intake and exhaust modifications to boost engine output, 17 x 9-inch wheels and 275/40ZR17 tires, and a host of suspension upgrades to create a world class performance vehicle.
The F-car received a number of factory upgrades for the 1998 model year. The all-aluminum LS1 V8 replaced the venerable LT1, the exterior appearance was a revised to inject modernity, and the basic anti-lock brake system was greatly improved to increase performance and service life. Four-wheel disc brakes became standard equipment on all F-cars. Racy, cast-aluminum, dual-piston calipers replaced the cast-iron, single-piston units up front, and front and rear rotor dimeter increased from 10.7 and 11.4-inches, respectively, to 12-inches all around.
Brake Component Choices
The abundance of new brake components for the ‘98-02 F-car covers the spectrum for all budgets and levels. Choices range from local parts store house brands to high-end and/or oversized aftermarket components available through mail order retailers or specialty manufacturers. Despite the overwhelming array of interesting options, we felt that since the performance of the factory-issued components was satisfactory and that OE fit and appearance were important factors in maintaining our Trans Am’s original appearance, we limited our search to high-quality stock replacements.
In a typical disc brake system, the brake pads are located within the caliper body and float freely on either side of the rotor disc. As input pressure is applied to the brake pedal, one or more hydraulically-actuated pistons within the caliper body compress the brake pads against the rotor surface. The brake pad creates friction against the spinning rotor, ultimately reducing vehicle speed. As miles accumulate, that friction, particularly when combined with an aggressive lining material can permanently deform the rotor surface.
For years mechanics used a special brake lathe to resurface the rotor face and remove all traces of lateral runout during a brake job. Manufacturers published a minimum thickness specification, and only once that was exceeded was rotor replacement required. While that still remains an option today, the cost of producing rotors has become so competitive that it’s generally more cost effective to simply replace a rotor than resurface it.
Our search for replacement rotors revealed a number of excellent option and Bosch’s QuietCast Premium Brake Rotor interested us most. Not only does it meet or exceed OE quality, it receives Bosch’s proprietary “Geomet” coating—a form of zinc plating that prevents corrosion just like our Firebird’s original rotors. No other stock-replacement rotor we found possessed the feature that we felt was important in maintaining an attractive appearance with our Trans Am’s open-wheel design. A complete set of Bosch rotors was on its way from our favorite mail order supplier.
Brake pads are made by bonding a frictional lining to a steel backing. Linings have been made from a variety of materials over the years, typically comprised of strands or particles embedded within a high-temperature resin. Regardless of composition, all brake pads emit dust as the lining wears during normal use. Not only does that dust create an unsightly appearance as it builds up on wheel surfaces, it can sometimes be caustic when servicing a vehicle’s braking system.
Asbestos was a very popular lining material for many years. Its excellent heat absorption and frictional qualities made it an obvious choice for high-performance applications. Growing concerns over the toxicity of asbestos dust forced brake manufactures to explore environmentally-safer solutions.
Non-asbestos organic (or NOA) materials began surfacing during the late ‘60s. The environmentally-friendly compound was softer and quieter, and generally easier on rotor surfaces, but wore quicker and required more frequent replacement. The organic lining wasn’t as effective as asbestos, however, and was susceptible to brake fade as heat built during aggressive maneuvers.
A metallic lining had been the choice for heavy-duty truck and full-race applications where ultimate stopping power was required. The metallic compound dramatically improves performance, particularly in high-heat conditions, but its effectiveness is greatly degraded when cold. Additionally, the hard pad lining and high-frictional quality was noisy and very hard on rotor surfaces.
Going into the ‘70s, some brake manufactures began offering brake pads with linings that combined organic materials and metallic particles. These “semi-metallic” brake linings proved an excellent compromise that delivered reasonable service life and excellent overall braking performance in myriad operating conditions. Semi-metallic brake pads went on to become the norm with automakers and service stations alike well into the ‘90s.
Going into the 2000s, brake manufacturers began introducing new lining technology to consumers. Adding ceramic fibers to the high-temperature resin and metallic compound produced a lining that performed exceptionally well, was equally effective hot or cold, easier on rotor surfaces extending their service life, and emitted lighter and finer dust that’s less likely to adhere to wheel surfaces. Because of these distinct advantages, it’s no surprise that ceramic pads have become the choice of many automakers today.
GM had been using semi-metallic brake pads on its F-cars for several years. It issued TSB numbers 99-05023-002A and 99-05-23-006 to dealership service staff in late 1999 that outlined procedural revisions when replacing noisy front and/or rear brake pads on F-cars produced between 1998 and midyear 2000. It seems that GM went from a semi-metallic lining to a ceramic lining in production at that point to reduce the risk of squeals and groans while stopping and recommended the same to solve customer complaints. We were convinced that a ceramic lining was right for us.
While exploring brake pad options, we found that Bosch offered its QuietCast Premium Disc Brake Pads with ceramic linings that meet or exceed OE performance criteria. It boasts a proprietary formulation of ceramic fibers, aluminum particles, and organic carriers. The lining is free of brass and copper, making it fully compatible with all current and future local and state laws. Bosch’s Molded Shim Technology combines steel and rubber backing shims that are permanently attached to the backing plate to increase durability and stability, and dampen noises. We added a set to our order and had everything on our doorstep in days.
Shock Absorber Choices
The front and rear shock absorbers that GM installed on its fourth-generation F-car were produced by de Carbon. The company was a hydraulic suspension system pioneer that reportedly developed the industry’s first monotube shock absorber nearly a century ago. The brand’s high-pressure monotube shocks with their distinctive orange paint became a mainstay in ’93-02 Firebird and Camaro applications with unique internal valving based on package requirements, and that includes those specific to WS6.
While GM’s 1993 – 2002 F-car featured a typical coil-sprung rear axle with independent monotube shock absorbers on either end, its front suspension is often incorrectly referred to as a MacPherson Strut design. A strut assembly simplifies underbody packaging with a coil-spring-and-shock absorber assembly that replaces the upper control arm and doubles as the steering pivot point in the front suspension. GM used the MacPherson strut in its third-generation F-car, but returned to a traditional upper- and lower-control arms in short-long arm design for the fourth-gen for its smoother responsiveness and predictability when combined with high-pressure shock absorbers in performance applications. The ‘93-02 coil-spring-over-shock-absorber assembly (or simply “coil-over”) has a single purpose, and that’s dampening.
There are dozens of excellent shock absorbers available on today’s aftermarket that are expertly designed for use with modified F-car suspensions. Since maintaining OE fit and appearance was paramount, we limited our search to replacements that met or exceeded the ride and handling qualities of our Trans Am’s original de Carbon units. There are only a handful of choices within those confines, and Bilstein’s B6-series was among them.
Bilstein’s B6 series is compatible with factory-installed coil springs and leaves original ride height unaltered. It uses proprietary gas-pressure technology to deliver the ultimate in performance while providing excellent ride quality at a very reasonable price. Past experience told us that we needn’t look further. We added a set to our order.
Installation
With all the new components on hand, we used a four-post lift for our install, but the same can be accomplished by securely supporting your vehicle on high-quality jack stands. Installing the new rotors and brake pads was straightforward without any real surprises. In less than two hours we had removed and reinstalled all of the rear end components and were ready to move onto the front.
The Trans Am’s front suspension proved more complicated. Not only did we have to transfer the coil spring and associated hardware from the de Carbon shock absorbers to the Bilsteins, we could only assess the condition of the ancillary wear items once the suspension was completely disassembled. Sourcing additional components added to the downtime, but it also kept us from rushing and making mistakes. Once we had collected everything needed and had the Bilstein shock absorbers loaded, we had our Trans Am’s front end reassembled in an afternoon.
As soon as we backed our Trans Am out of the garage for the initial test drive, we were extremely pleased to find that it sat just as before. After a few low-speed stops to seat the new brakes and make sure the suspension was installed correctly and functioning properly, we headed out onto the main streets for first impressions. We found that ride quality had noticeably improved. Road imperfections were less upsetting and once we were able to reach higher speeds, roll control while cornering increased dramatically. Applying the brakes provided smooth and predictable performance without any pulling or shuddering. Success!
Conclusion
While installing new brakes and shock absorbers on your ’93-02 F-car requires a methodical approach that should allow some downtime to source wear items and possibly outside assistance, the actual time we spent working on Trans Am totaled less than a day. The effort produced notable improvements in braking, and ride and handling quality when compared to the worn originals. Best of all, it made our Trans Am more pleasurable to drive and reaffirmed our belief the GM’s fourth-generation F-car remains one of the best performance values on the road today.
Sourcing New Caliper Fasteners
A little-known fact when performing a brake jobs is that GM states in its service literature that its caliper pin and caliper mounting bracket fasteners should never be reused. As opposed to a torque-to-yield design where a fastener’s intended load can be applied only once, GM’s practice is more likely intended to prevent the possibility of thread damage or improper reinstallation by careless owners or technicians that could impede an otherwise-reusable fastener’s ability to maintain its intended clamping load in service. Serious injury or death could result should a brake system failure occur.
Bolt numbers-14067559 (front and rear caliper pin) and -18060356 (front caliper mounting bracket) for our 1999 Firebird were readily from our local GM parts counter for a few dollars each, and they included a pre-applied locking compound on the threads. We torqued them to spec and all was well. The rear caliper mounting bracket bolt (10229606) proved a significant challenge, however. It seems that bolt had been discontinued by GM in 2009 and OE- replacements aren’t available. The bolt’s specifications suggest it’s little more than a 10.9-grade, metric hex flange screw in M12 x 28 x 1.75 sizing with black oxide coating.
Without exact replacements available, we were left with two reasonable options to reinstall the rear caliper mounting brackets. We could source a similarly sized new bolt from a fastener retailer or reuse our Firebird’s originals. It seems that the closest 10.9-grade metric hex flange screw available is in 30-mm length as opposed to the 28-mm original, and a thin shim beneath the head could be used to take up the variance. After looking our originals over closely, however, they appeared to be in excellent condition. We decided to reuse them. In doing so we first cleaned the threads with an appropriately-sized die, and then carefully torqued them to recommended specification using an accurately-calibrated torque wrench. Blue-thread locking compound is required in either instance.
We haven’t had any issues reusing our Trans Am’s original rear caliper mounting bracket bolts so far, but we need to make clear that whatever path you decide to take with your project is at your own risk. Periodic inspection to ensure your safety is highly recommended.
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