The latest generation of Chevrolet Camaro is an amazing performance vehicle. Its blend of power, handling, and aggressive looks is like nothing else available today. Although the car is stout from the factory, there still is room for improvement. The Camaro’s independent rear suspension (IRS) works well, but some of the links are rather flimsy, most of the bushings do nothing to help performance, and the whole system can leave much to be desired when pushed to the limits. Even though most new Camaro owners don’t have plans to push their cars near that limit, there are still many areas where improvements can be made that will benefit the people who simply drive back and forth to work.
BMR Suspension of Seffner, Florida builds a plethora of suspension components for Chevrolet’s latest iteration of the Camaro. Over the past year, we have shown you many different components from the suspension manufacturer, and the list of parts continues to grow. Whether you have a basic daily driver or an all-out race car, BMR has the part needed to make your car work in any performance application.
Wheelhop is a parts killer. There are a few root causes, most based around oscillation within the suspension system. wheelhop can be caused by a variety of things, from the wrong shocks to a better or worse surface than the tire can handle, or more power than the tire can lay down. But the biggest factor is bushing deflection within the suspension system.
Bushing deflection and suspension link deflection causes the rear tires to grip and slip at an extremely rapid rate. In an IRS car, you would see cradle bushing deflection and differential bushing deflection, which creates large amounts of movement within the system that causes the tires to lose traction and then gain traction and lose traction and gain traction.
When uncontrolled, wheelhop can break everything from the differential housing to axles, ring and pinions, and even the welds on control arms. It can be extremely violent. But controlling wheelhop isn’t overly difficult. By upgrading certain parts, you can limit the deflection that leads to wheelhop, but there is a catch—additional noise, vibration, and harshness.
Noise, Vibration, and Harshness
NVH is an extremely subjective topic. NVH (noise, vibration, and harshness) is different to everyone, as people have different tolerances for what is deemed acceptable. The sources of NVH in a vehicle consist of engine, driveline, suspension, brakes, and tire and road noise. Softer bushings will absorb most of this noise, but as you increase the stiffness, more noise can be transferred into the passenger compartment.
Because NVH can ruin a great car, BMR Suspension offers a wide range of parts to meet any performance level, while still offering customers reasonable NVH levels.
When it comes to improving the sixth-gen IRS, few things make a more significant impact than cradle bushings. The factory cradle mounting bushings are made from very soft rubber and have large voids in them. GM does this because the softer these bushings are, the less NVH will be transmitted into the driver compartment. While this is great for the people who just want a comfortable, cushiony ride, it is horrible for anything performance related. The bushing deflection causes the cradle to shift in just about every direction under the car, leading to a disconnected feeling for the driver. While this might not be noticeable to most people while driving under normal conditions, when you put the car in a situation where there are larger lateral loads on the suspension, this change in feel can be much more pronounced.
By upgrading the cradle bushings to a harder material like polyurethane or Delrin, you reduce or eliminate this deflection. This gives the driver a much more connected feel. It also gives the driver much more confidence in the car’s ability to maintain grip. Limiting the amount of cradle movement under the car also allows the suspension components to work they way they were intended to. The links will see reduced bind, and rear tire alignment will remain more consistent.
When it comes to IRS Cradle Bushings from BMR Suspension, you have some options. You can go with a lockout kit, polyurethane bushings, or Delrin bushings. Each will give you a different level of performance with different NVH levels.
BMR’s Cradle Bushing Lockout Kit is a great kit for people looking to improve performance but don’t want significant gains in NVH. The soft cradle bushings with voids are a massive contributor to wheelhop, but many people don’t want to change bushings for a street car. When BMR started looking at the cradle bushings and how the cradle attaches to the car, it realized there really wasn’t much locating the cradle and this caused much of the deflection.
BMR designed the kit to capture the top and bottom of the outer bushing cups on the cradle, as well as the inner sleeve of the cradle bushing. This greatly reduces fore, aft, and lateral cradle bushing deflection. There is a stainless plate that mounts on the bottom side of the rear bushing, which prevents vertical cradle movement. The cradle bolts to the car with the factory support braces or BMR CB008 cradle braces.
If you require a higher level of performance than the lockout kit offers, polyurethane bushings might be the way to go. This is a great option for enthusiasts looking for bigger performance gains, while keeping NVH at a conservative level. BMR uses 95-durometer polyurethane, which greatly reduces bushing deflection. These bushings are still soft enough to isolate NVH from the driver’s compartment. Polyurethane is far superior to OEM rubber for bushings. It doesn’t deflect nearly as much, and it will survive exposure to petroleum products, road salt, ozone, and other elements of the harsh undercar environment suspension bushings live in. BMR Suspension’s Polyurethane Differential Bushings reduced differential movement and pinion rise over the factory rubber bushings, helping to keep wheelhop in check.
If performance is the only thing on your mind and noise doesn’t matter, BMR’s Delrin cradle bushings are the way to go. Delrin is a solid polymer that completely eliminates bushing deflection. Delrin bushings will lock the cradle in place, but will have the most significant increase in NVH. These are designed for max-effort applications where performance is everything.
When power is applied and transfers to the differential, the differential bushings deflect. This causes the differential to rotate (the pinion rises and the rear of the housing drops). This rotation absorbs power, which causes the car to react slower to power application. It also changes the pinion angle, which is not as important in an IRS as it in a solid axle car. Changes in pinion angle can affect NVH, but with the IRS will not be as critical for power application.
When it comes to differential bushing upgrade options, BMR offers similar options as the cradle—an insert kit, polyurethane, and billet aluminum bushings. When you start changing bushing material in the differential mounts, increases in NVH are much more pronounced. The factory rubber bushings absorb very large amounts of gear noise and drivetrain noise, and increasing the stiffness of these bushings reduces how much is absorbed. It is important to keep in mind that most differential bushing upgrades will improve performance, but NVH will also be increased.
Differential Bushing Insert Kit
For the street performance enthusiast that might go to the track infrequently, but wants an increase in performance, BMR offers its differential bushing insert kit. This kit consists of CNC-machined billet aluminum bushing inserts and plates to fill the voids in the bushings, as well as limit the amount of deflection in the bushing. This kit requires a non-permanent installation, so if you sell the car or want to upgrade, the kit can be easily removed. Although there will be a gain in NVH, the factory bushings still absorb a good amount of noise, making these a good option for daily-driven cars.
The next level of performance is replacing the factory rubber bushings with polyurethane bushings. Again, BMR’s polyurethane differential bushings are 95-durometer. This material greatly reduces deflection and increases performance. Unfortunately there will be some increase in NVH with these bushings, but the increase in noise is offset by the increase in performance. These solid polyurethane bushings limit pinion rise, increasing throttle response, while still remaining soft enough to absorb some NVH.
Billet Aluminum Bushings
For max-effort applications, BMR’s billet aluminum differential bushings are the way to go. These CNC-machined bushings lock the differential in place, completely eliminating bushing deflection and pinion rise. This is the ultimate in performance, but every bit of gear noise from the differential will be transmitted into the driver’s compartment. This kit is usually recommended for racecars or other applications where noise is not a concern.
Rear Suspension Links
When the sixth-gen Camaro was designed, one of the big changes was a reduction of weight. Although the overall mass of the car was dropped, things like suspension components also played a part in the car’s weight reduction. Weight reduction is certainly a good thing, but when it comes at the cost of strength and integrity of the suspension links, it can be an issue. We have seen the upper and lower trailing arms off the car, and they are flimsy enough to be twisted by hand. This means that as power is applied to the chassis, these links can deflect causing alignment changes and inconsistent handling characteristics. On the other hand, the upper and lower control arms are quite beefy for stamped steel components. Upgrading these links for added adjustability or to remove a soft rubber bushing, while adding the strength of a boxed or round tube part can make a big difference in performance.
The factory toe rods have a couple of inherent flaws when used in the performance world. Most notable is GM’s use of rubber bushings. These soft bushings deflect, allowing the toe rods to move. This causes inconsistent dynamic toe settings in the rear, which will lead to poor feel for the driver. GM also uses eccentric bolts to handle the adjustments. And while this makes it nice and easy for the alignment guys, these eccentrics can move during aggressive maneuvering or when launching with big power and sticky tires.
The toe rods are more important than most people realize. If there is any deflection in the factory toe rod or toe rod bushings, that deflection is directly transferred to the alignment of the rear wheels. BMR’s adjustable toe rods are built to be very strong, and that is intentional. The goal was to eliminate as much deflection as possible. This is why BMR uses heavy-duty rod ends and eccentric lock out plates. The eccentric bolts make alignments fairly simply, but if you have more than factory power levels and sticky tires, the eccentrics don’t do a good job of keeping the alignment consistent. The eccentrics can move under aggressive straight-line acceleration also, so drag racers aren’t safe from toe changes either. By eliminating the eccentrics and using the arms for the adjustments, you add a large amount of consistency to the rear alignment. This is also one of those parts that do not contribute much to NVH. This allows BMR to solid mount the arms with minimal increases in NVH.
The upper and lower trailing arms are the flimsiest parts on the sixth-gen’s IRS. We alluded to the fact that the arms can be twisted by hand earlier. Upgrading these links does a lot for straight-line traction. Reducing bushing and link deflections keeps the rear wheel alignment more consistent, keeping the tires’ contact patch more consistent. These arms also help alleviate wheelhop in higher horsepower applications. BMR offers three versions of these links—a non-adjustable version with polyurethane bushings, a single-adjustable version, and an on-car adjustable. Both adjustable versions feature heavy-duty Teflon-lined rods ends. BMR tells us most people are fine using the non-adjustable version. The on-car adjustable version are recommended for enthusiasts that are going to race their Camaro on a regular basis and make frequent alignment changes. The single-adjustable versions are for enthusiasts looking to eliminate a bushing and solid mount the links.
Upper Control Arms
The upper control arms are very similar to the trailing arms, but play a different roll in the system. The upper control arms have a larger impact on rear wheel alignment—primarily with camber. If you are going to autocross or road race your Camaro, these are a must. The upper control arms will take the brunt of the lateral loads applied to the chassis during cornering situations. This makes having a very strong part extremely important. Depending on how much you plan on racing, adjustability might be just as important. For these enthusiasts, BMR offers single- and on-car adjustable versions featuring the same high-quality rod ends.
Aside from controlling body roll, sway bars also play an important part in the balance and handling feel of a car. By increasing the sway bar rate of the front or rear sway bar, you change the car’s understeer and oversteer characteristics. This is the difference in having a good handling car, and a great handling car. This is also subjective as different drivers like different feels. Because of this, BMR offers both adjustable and non-adjustable sway bars.
Changing the sway bar rate and spring rate will have the same effect on body roll, but when you increase spring rate, ride quality is negatively affected. When you add sway bar rate, that rate is only applied to the chassis when the body is rolling over in a turn. The sway bar’s torsional force helps to keep the body flat and level without giving you an overly harsh ride.
Adjustable sway bar endlinks allow you to do a couple of things. They are stronger than the factory links, which you want in handling applications. The amount of force exerted on the endlinks is unbelievable. They keep a 3,500-plus pound car from twisting as you push it around a turn as hard as possible. Any deflection in the sway bar endlinks is a reduction in sway bar rate applied to the car, and that means more body roll. BMR’s adjustable ends are designed to do two things: be stronger than stock, and allow you to keep the sway bar geometry correct. Sway bars are designed to operate at a certain working angle (for most applications this is parallel to the ground). When you lower your car, the working angle of the bar changes and this can affect the effectiveness of the bar. Having an adjustable endlink allows you to change the working angles of the sway bar for optimal performance. Adjustable endlinks allow you to correct these working angles for optimal sway bar performance.
Stiffening the chassis on just about any car can be an almost controversial topic. Some people swear by it, others think it’s a waste of time, money, and weight. One of the great things about the sixth-gen Camaros over the fifth-gens is the increased chassis rigidity. While this is beneficial to everyone, for the hardcore track crowd, an even stiffer chassis is achievable. The Camaro comes with some bracing from the factory, but it is all formed from fairly thin stamped steel. The stamping adds some strength, but any real chassis flex will just twist these braces.
For this reason, chassis stiffening may only be a real option for the hardcore handling enthusiast. Sure, there is some aesthetic value to a strut tower brace, but it will not amount to a significant difference in handling for daily use.
The Wrap Up
There is no doubt that GM hit a home run with the sixth-gen Camaro, but it isn’t a grand slam. The manufacturer’s primary focus is selling cars to the masses, not solely for performance enthusiasts. This means there is room for improvement in the performance department. Thankfully there are companies like BMR Suspension that put the time and effort into finding the weak links and engineering parts to correct the issues and improve the car. With such a great car, we can’t wait to see just how good it can be!
Ed note: This story was written by contributor Pete Epple, an employee of BMR Suspension. While the article does feature BMR products, we felt that the value of the information outweighed any negatives from this relationship.