Last time around, I described shock absorbers as a “lowly” part of your Corvette, an oft-forgotten suspension piece that could use an upgrade. Perhaps lowly wasn’t the right word, because this month’s topics are so obscure, many owners don’t even know they exist — much less consider changing them. But like shocks, these components can make a big difference in how your ride handles. Ladies and gentlemen, meet the most invisible performance parts on your Corvette: its bushings.
Depending on your Corvette’s model year, it will use bushings in some or all of the following suspension pieces: front and rear control arms, front and rear sway bar mounts, front and rear endlinks, rear leaf spring, and ball joint and tie-rod boots. Other bushing locations can include the power steering ram and differential carrier. Mounts are always used for the engine, transmission, and body — they’re different kinds of bushings that are lumped in with suspension bushings.
When it comes to spending money on car parts, it doesn’t get more un-sexy than replacing some rubber doodads that cushion some things and help control other things somewhere under your car. Further complicating matters, properly functioning factory bushings do a damn good job during normal driving — after all, their rubber construction lets them soak up bumps, quell vibration, and be mouse-fart quiet in the process.
But those soft rubber bushings are a compromise, just like any other OEM part on your Vette. Which means maneuvers any more spirited than a turn-arrow blast bring about bushing deflection, lost camber, and unpredictable handling. And just like your uncle Mike at Thanksgiving dinner, you’ll have lots of body roll and unresponsiveness.
And that’s when they’re brand new. Rubber bushings break down over time — regardless of your Vette’s mileage — and road salt, oil, and other contaminants accelerate that breakdown. Throw in the fact that your chassis’ and suspension’s immense forces can permanently disfigure these bushings, and your handling and control problems can eventually turn into a safety issue.
New replacement rubber bushings are rare — if you drive a late-model Vette, you might only find rubber bushings for your sway bars. So since your only other option is to get used rubber bushings from a wrecked Corvette (which isn’t the best idea), you should consider aftermarket bushings. They’re new, they give higher performance and longer life compared to rubber, and save for labor costs, they’re pretty affordable. Here’s what you need to know.
Construction
Automotive bushings can be constructed from one of several different materials, depending on what the intended use is. Rubber bushings are factory installed in vehicles worldwide, and aftermarket replacements can be made of polyurethane, hard plastics, and even aluminum. Bushings can be very soft or very firm, as explained in our Bushing FAQ section below. The following are the different types of bushings:
OEM Rubber
Factory bushings are made of rubber, a natural material harvested from certain kinds of tropical trees. Rubber bushings are soft, around a 60-65 Shore A rating, and they flex and rebound as your chassis and suspension moves, exhibiting very little noise, vibration, or harshness (NVH) in the process.
However, as mentioned in the intro, those same properties make your Corvette less responsive during serious performance driving or racing. And don’t forget that rubber is biodegradable and will break down over time.
Polyurethane
Unlike natural rubber, polyurethane is a man-made plastic. This material is both elastic and strong, and can be formulated to be very soft, extremely hard, or anywhere in between. Polyurethane bushing hardness usually ranges from just slightly harder than rubber (around 70-80 Shore A rating), to firm (around 80-90 Shore A rating), to very firm (around 95 Shore A to the harder Shore D rating). And unlike rubber, it’s immune to age- and contaminant-related breakdown.
One of polyurethane’s biggest “drawbacks” is its bad reputation from decades ago. Back then, poly bushings were in their infancy: they were too hard and too harsh-riding, and they squeaked incessantly. Thankfully, today’s polyurethane is much more advanced: many street poly bushings are only marginally harder than rubber, but retain poly’s quicker response, higher load-bearing capacity, better tear strength, and stronger abrasion and contaminant resistance. Some companies offer graphite-impregnated, self-lubricated poly bushings too, but in most cases, when regular poly bushings are installed and maintained correctly, they don’t squeak anyway.
Delrin
Delrin is an advanced acetal resin — fancy talk for plastic. But this is no ordinary plastic; it’s a versatile engineering plastic with metal-like properties. They include high strength; stiffness; fatigue endurance; moisture, gasoline, solvent, and chemical resistance; excellent dimensional stability; and a wide temp range.
Delrin bushings are harder than poly bushings, and are rated on the hardest Rockwell scale. As Delrin effectively bridges the gap between plastics and metals, it’s a great option for racers who want more hard-core performance, yet don’t want the full-on NVH issues of aluminum bushings. And speaking of NVH, one cool feature of Delrin bushings is their natural lubricity — they’re self-lubricating!
Aluminum
Before you dismiss aluminum bushings as a crazy, race-only option, remember that early C3s actually used aluminum body mounts. Of course, they pretty much rode like race cars, too. (HEY-OH!)
Unless you’re looking for stock-replacement C3 body mounts, your Corvette should only use aluminum for things like high-performance steering bushings and aftermarket bushing sleeves. The stuff’s too damn hard for your street or street/strip Corvette, and Delrin or polyurethane have you covered.
Operation
For a small piece of malleable material, a bushing’s job is very complex.
“Bushings are a critical component of a vehicle’s suspension,” starts Energy Suspension engineer Ben LaHatt. “They serve multiple purposes. In fact, in any specific position three or four different physical demands are being placed on these pieces.
“First, bushings keep the suspension positioned correctly to avoid misalignment of the wheels. Second, they reduce the movement — or deflection — of the suspension components relative to the chassis to maintain proper wheel alignment. Third, they help absorb irregularities and imperfections in the road, and reduce the harshness that could be felt throughout the vehicle. Automotive manufacturers spend countless hours developing techniques to reduce a vehicle’s Noise, Vibration, and Harshness, or NVH. This always comes as a compromise of increased deflection from rubber bushings in order to reduce NVH.
“And finally, they deal with a hostile environment. They’re subject to extreme changes in temperature, and exposure to a great number of chemicals and foreign materials, while still maintaining all the previously mentioned characteristics.
“Bushings alone can completely change the driving characteristics of a vehicle, from feeling mushy, soft, unpredictable, noisy, and overall dangerous, to stable, consistent, predictable, quiet, and altogether safer.”
Applications – What’s Available For Your Vette
As is usually the case with aftermarket products, C4s, C5s, and C6s have the most aftermarket replacement bushings and race-ready upgrades. C7 parts are starting to come online as well.
C3s have a decent number of parts available, but not as much as the newer cars.
But due to age, collectability, and value, C1s and C2s just don’t have as many aftermarket options. However, shops like Art Morrison and Jim Meyer Racing Products will build you a custom performance chassis for these model years. And while they’re juuussssst a tad more expensive than a bushing kit, they’ll definitely give your classic Vette 21st century handling.
Bushing Guide
If you’re ready to replace those worn-out factory bushings for something better, the following companies probably have what you’re looking for. We’ve included a mix of street-friendly polyurethane body and suspension bushings, street/strip upgrades like Delrin or aluminum steering rack bushings, and more hard-core race upgrades like control arm bushing and sleeve kits.
Note that earlier Vettes don’t have as many bushing options — however, several companies make complete replacement chassis that make those classics handle like new cars. Prices listed are either provided by the company or taken from an online store.
Energy Suspension
Energy Suspension has been a leader in performance polyurethane suspension technology since 1983. Dedication to manufacturing and developing superior products has established Energy Suspension as the most asked-for name in performance polyurethane bushings and mounts today. Energy Suspension’s proprietary Hyper-Flex polyurethane formulas set high industry standards, and with in-house engineering, chemical formulation, molding, and final packaging, it produces a genuine American-made product for its customers. Energy Suspension has products for C2 through C6 Corvettes.
www.energysuspension.com
C2/C3 Master Set
Material: Polyurethane
Part Number: 3.18123
Price: $394
Details: Set includes the following:
Front Control Arm Bushings Part No. 3.3108, Front End Links Set 9.8120, Power Steering Ram Bushings 3.10102, Transmission Mount 3.1108, Differential Carrier Bushings 3.1101, Ball Joint End Boots 9.13125, Tie Rod End Boots 9.13101, Rear Control Arm Bushings 3.3191, Rear Spring Cushions 3.2104, Rear Strut Rod Bushings 3.7102 and 3.7101, and Rear Sway Bar and Endlink Bushings for 7/16-inch bar 3.5153.
Notes: Must reuse outer metal shells on C2 & C3 rear control arm bushings. Add R for red or G for black to each part number. To prevent bushing squeak, prep parts properly and use included Prelube 5 grease when installing. May have to re-grease every 3-5 years depending on driving conditions.
C2/C3 Motor and Trans Mounts
Material: Polyurethane
Part Numbers: 3.1133 (chrome finish), 3.1120 (zinc finish)
Price: $154 (chrome), $92 (zinc)
Details: While doing a Master Set, you might as well replace the mounts. An upgrade for your soft, tear-prone rubber mounts. Strong enough for race use, yet still absorbs vibrations for street use. Incorporate an interlocking feature that mechanically keeps the mounts from separating if there is a failure.
Notes: Add R for red or G for black to each part number. Available for 305, 327, 350, and 396 engines.
C4 Master Set
Material: Polyurethane
Part Number: 3.18122
Price: $375
Details: Set includes the following:
Front Control Arm Bushings Part No 3.3142, Rack and Pinion Bushings 3.10101, Differential Pinion Bushings 3.1103, Ball Joint End Boots 9.13127, Tie Rod End Boots 9.13101, Rear Control Arm Bushings 3.3145, Rear Spring Cushions 3.2123, Rear Strut Rod Bushings 3.7107 and 3.7108.
Notes: Add R for red or G for black to each part number. To prevent bushing squeak, prep parts properly and use included Prelube 5 grease when installing. May have to re-grease every 3-5 years depending on driving conditions.
C5 Bushings (Non-Master Set)
Material: Polyurethane
Part Numbers: See Below
Price: See Below
Details: Available C5 bushings include the following:
Front Control Arm Bushings Part No. 3.3176*, $48
Rear Control Arm Bushings 3.3177*, $53
Rear Spring Cushions 3.2140, $13
Front 23mm sway bar bushings 3.5200, $12
Front 26mm sway bar bushings 3.5196, $12
Tie Rod End Boots 9.13101, $3
Notes: *Must reuse all metal parts (shells) on C5 and C6 front and rear control arm bushings. Add R for red or G for black to each part number. To prevent bushing squeak, prep parts properly and use included Prelube 5 grease when installing. May have to re-grease every 3-5 years depending on driving conditions.
C6 Bushings (Non-Master Set)
Material: Polyurethane
Part Numbers: See Below
Price: See Below
Details: Available C6 bushings include the following:
Front Control Arm Bushings Part No. 3.3176*, $48
Rear Control Arm Bushings 3.3177†, $53
Notes: *Must reuse metal shells, and excludes Z06, ZR1, and Grand Sport. †Must reuse metal shells
Doug Rippie Motorsports
Doug Rippie Motorsports (DRM) has been making Corvettes quicker and faster since 1992, and has a World Challenge and Corvette Challenge racing pedigree as well. DRM is known for getting race car performance out of drivable and street-legal Corvettes, no small feat.
One way DRM does this is with its aluminum or Delrin steering rack bushings, which replace the rubber mount to combat the C5/C6’s numb steering feel.
www.dougrippie.com
C5/C6 Steering Rack Bushing
Material: Aluminum, Delrin
Part Numbers: N/A
Price: $39.95
Details: Helps to provide more connected, precise steering feel.
Notes: Fits base car, Z51, and Z06. If racing class rules prevent aluminum, use the Delrin version.
LG Motorsports
LG Motorsports (LGM) was founded in 1988 by racer Lou Gigliotti during the Corvette Challenge series. Its products are a direct result of the racing program, and are tested to be the ultimate in performance and reliability for track and street use. The LGM team puts this philosophy into everything they do and produce. While items like the Monoball control arm housings are considered track-only upgrades, LGM offers many track-tested parts that work just fine on the street.
www.lgmotorsports.com
C5/C6/C7 LG Monoball
Material: Aluminum
Part Numbers: SKU-1981
Price: $1,795.95
Details: Lightweight aluminum housings for Teflon lined bearings, which replace weak OEM rubber bushings and remove any deflection in the suspension. This allows true alignment, and more consistent results on track.
Notes: Fits all C5, C6, and C7 cars, including Z06 and ZR1 models. Installation available.
QA1
QA1 is well known for its shock absorbers, but the Minnesota-based company also builds some killer rod ends for serious street and race Corvettes.
Stock suspension bushings can bind, and they absorb some of that all-important suspension feedback needed for optimum lap times. QA1’s two-piece Endura X Series rod ends get rid of bind and resistance, which allows the suspension to work more efficiently. This two-piece, ball-and-body design utilizes high-strength chromoly steel. This allows them to stand up to immense push and pull loads (and unexpected side loads) found in heavy, link-suspension street and track cars like Corvettes. And they self-seal and self-lubricate, too.
www.qa1.net
2-Piece Endura X Series Rod Ends
Material: Chromoly
Part Numbers: N/A, depends on dimensions
Price: $8-60
Details: Contact QA1 to determine the correct part number for your Corvette.
Notes: QA1 recommends its 2-piece X Series ends over the 3-piece versions for street/race Corvettes. Male and female ends available. Self-lubricates without the need for zerk fittings.
AFE Power
Advanced FLOW engineering (aFe) is a manufacturer of automotive cold-air intake systems, performance air filters, fluid filters, intake manifolds, turbochargers, programmers, throttle body spacers and exhaust systems. aFe was founded in 1999 and is headquartered in Corona, California. Pfadt Race Engineering is now part of advanced FLOW engineering, and produces high-end performance parts for GM vehicles.
www.pfadtracing.com / www.afepower.com
aFe Control PFADT Series Drag Rear Solid Spherical Control Arm Bearings Set
Material: Aluminum (sleeves), spherical bearings
Part Numbers: 460-401002-A (C5/C6), 460-401004-A (C6 Z06)
Price: $1,194-1,314
Details: Replaces all 10 rear control arm bushings with mono-ball, spherical joints to eliminate friction and deflection. 6061-T6 aluminum bearing housings feature a Mil Spec, high corrosion resistant anodizing. CNC machined, heat treated, 17-4 PH stainless steel shafts, CNC machined 6061-T6 articulation spacers. High articulation spherical bearings with over 108 components. No machining or welding required. Replaceable FK bearings are Teflon lined for minimum friction and zero maintenance. Highly recommended for dedicated track cars, not recommended for street cars.
Notes: 460-401004-A set for C6 Z06 shown.
aFe Control PFADT Series Control Arm Bushing/Sleeve Set
Material: Aluminum (sleeves), graphite-impregnated polyurethane (bushings)
Part Numbers: 470-401001-B (C5/C6, for Base, Z51, GS), 470-401002-B (C6 Z06/ZR1 ’06-13)
Price: $540-660
Details: Reduces bushing deflection to improve handling, and offers a comfortable ride suitable for both track and street use. 6061 hard-anodized T6 aluminum, combined with a micro-porous surface for excellent grease retention. Specially grooved, graphite-impregnated polyurethane bushings for superior grease retention and quiet operation. Snap ring and plate system adds strength and stiffness to front upper control arms, and eliminates bushing failure.
Notes: 470-401002-B set for C6 Z06 and ZR1 shown.
Bushing FAQ
We, like you, had lots of pressing questions about bushings. So we reached out to Energy Suspension’s Ben LaHatt, an engineer who’s forgotten more about bushings than we’ll ever know. We asked, he answered, and we’re all smarter for it. You’re welcome.
Vette: Why should Corvette owners replace their bushings?
Ben LaHatt: Bushings are often not the first thing people think of replacing when upgrading or restoring a vehicle, but they can be some of the most beneficial and economic upgrades to a vehicle’s suspension. Polyurethane bushings are a performance upgrade as well as a replacement to OEM parts, but do not duplicate OEM characteristics. Polyurethane is designed to be stronger than OE and rubber replacement parts, and may magnify other weak areas too.
Vette: Please describe what Energy’s poly bushings do to suspension and chassis components, compared to OEM bushings.
LaHatt: Every application is unique, from control arms to leaf springs and from differential mounts to engine mounts. Energy Suspension’s polyurethane is designed to improve articulation when needed, reinforce components for proper positioning and wheel alignment, withstand the environmental forces it may encounter, and take consideration into NVH and how that may affect driving performance and quality. Polyurethane upgrades are exactly that, upgrades. Handling performance and drivability of the vehicle will often improve, which is what they were designed to do.
Vette: Enthusiasts often discuss how “hard” or “soft” a bushing is. What is hardness, or Shore rating?
LaHatt: Hardness, or durometer, is a measurement of how much a material will deflect under a specified load. There are multiple Shore scales, but polyurethane is almost always measured in the Shore A scale. This specific scale ranges from being gummy soft like a rubber band, to the firmness of a skateboard wheel. Energy Suspension’s polyurethane blends range in durometer from 70 Shore A up to 96 Shore A, and are based on the specific application of that part.
Vette: What is a broad Shore rating range of rubber, poly, Delrin, and aluminum?
LaHatt: Rubber and polyurethane bushings cover a broad range of durometers within the Shore A scale. Rubber can often be softer in the scale than polyurethane, and reversed at the top, with polyurethane having a higher possible durometer than rubber. Delrin is a crystalline plastic that is measured in the Rockwell hardness scales. Aluminum is also measured in the Rockwell scales. The Rockwell scales range from plastics to metals and are much harder than anything made of polyurethane. From an automotive and suspension standpoint, Delrin and aluminum are considered solid mounted and give no consideration to NVH.
Vette: With a car’s chassis and suspension in mind, describe which types of poly bushings usually have harder Shore ratings, and which have softer ratings.
LaHatt: Depending on the application, durometers can vary even when used in the same position. There are general principles we’ve found to work best in certain areas, and most components use a mid-level durometer. In applications where stronger forces are present, higher durometers are used to reduce deflection. Areas that need to maintain some degree of isolation from the drivetrain to the chassis will see a softer durometer to maintain acceptable NVH levels. Body, engine, and transmission mounts tend to need softer durometers because they are responsible for reducing significant amounts of NVH.
Vette: What materials and chemicals are used to make a bushing?
LaHatt: Part of what makes Energy Suspension’s polyurethane blends stand out from all other competitors is our proprietary formulations that continue to be a closely guarded secret. Polyurethane is typically mixed together with a minimum of two separate chemicals, but can also include many other chemicals for different characteristics, including tensile strength and color. We’ve been developing different blends of polyurethane for over 30 years, and are still testing out new formulations to further increase certain physical properties while maintaining all our current high-quality characteristics.
Vette: Can you give a quick explanation of how bushings are made?
LaHatt: Polyurethane material is mixed in a process commonly outlined as having an “A” and “B” side. Both of these liquid sides, or chemicals, are heated and pumped through a mixing unit, which is then immediately injected into a mold. These molds are designed and developed in-house and are also a proprietary operation. After a certain period of time, the liquid material hardens to a pliable solid state and is then removed from the molds. The molds are then reused to start the molding process all over. Once the polyurethane part has completely cured over a specified amount of time, the individual parts can then be trimmed and dimensioned as needed for final approval, and are then ready to be packaged and shipped to the customer. This process takes place over multiple days in order to create a quality performance part that is designed to last.
Vette: Describe how today’s poly bushings are light years beyond the harsh, squeaky poly bushings from a couple decades ago. What changed?
LaHatt: Our blends of polyurethane are continuing to evolve and advance beyond what was originally derived over 30 years [ago]. Some of the original materials are still being used to this day, but we’ve expanded our range of products and materials to encompass a greater variety of applications. Along with improvements to the materials are the design standards that are now incorporated into new products. Throughout the years we’ve done a lot of testing, and taken lots of feedback from customers who use our products continually. So we’ve been able to identify more critical areas to incorporate improved designs and add specific details, such as improved grease handling, to fine tune the intended use of our materials.
Vette: What type of grease is used with your bushings, and why?
LaHatt: We use a pure, synthetic grease that is waterproof and highly adhesive. The pure synthetic properties give it great lubrication qualities, while being highly adhesive and waterproof ensure the grease will stay in place well after installation is complete.
Vette: What kinds of installation tips should be followed when installing poly bushings?
LaHatt: Make sure your vehicle’s suspension components are in good working condition, as polyurethane will not fix a physically damaged component. And always read the instructions and check the parts lists before starting on an installation. FYI, Energy Suspension’s R&D team test fits and installs every kit in-house so we can assist the customer with their installation experience.
A few other tips and tricks that are helpful for installation include:
• Having access to certain shop tools like an arbor press and a hydraulic shop press
• Working in a clean environment to eliminate the potential exposure of foreign contaminants
• Cleaning and greasing every area on the vehicle that encounters a moving polyurethane part during installation
• Having WD-40 and shop towels handy, to clean up excess grease
• Having a factory service manual and Energy’s customer service number on hand for removal, reinstallation, and suspension component torque specifications
• Double-checking your work before setting off down the road
• Having a professional shop do the work for you if you feel the kit requires more tools and knowledge than you might have. Many times, they’ve installed kits like this already, and can complete the task quickly and efficiently without any great risk
Vette: What kind of re-greasing interval should owners follow, and what environmental or vehicle-use situations call for more frequent re-greasing?
LaHatt: It really depends on vehicle use and environment. It’s difficult to prescribe a specific maintenance interval for greasing and inspecting our products. One way to know if grease is no longer lubricating is if the bushings begin to squeak. At that point you’ll know it’s time to re-grease them. Inspection at regular intervals, such as during oil changes and other factory maintenance schedules, is encouraged. These products can easily last the life of the vehicle if they are lubricated and maintained properly. Encountering harsh or rugged environments such as sand, snow, mud, racetracks, and general off-road use requires more frequent inspection and re-greasing.
