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Old 09-15-2012, 10:29 PM  
VIR Specialist

JusticePete's Avatar
Drives: Camaro Justice
Join Date: Jun 2007
Location: Virginia
Posts: 20,249
Foundational 5th Gen Required Upgrades

Foundational 5th Gen Required Upgrades

There is a noticeable rear end step out in turns while applying power or brakes and dealing with bumps in the 5th Gen. This is due to the voids in the OEM Sub-frame bushes. It is not unique to the Camaro. It is typical of IRS systems installed with rubber bushes to isolate the passenger area from road noise. Sub-frame bushes are a foundational component of the IRS and the most important modification that can be made to a 5th Gen. If you add more power it will place more load on the sub-frame bushes and amplify rear end step out / rear end steer. Lower the Camaro's CG with lowering coils and rear end step will be more pronounced. The larger and stickier your rear tires the more pronounced the sub-frame movement becomes. If you set your fence posts in Jello the finished fence will wiggle like Jello. Your OE sub-frame bushes are nothing like Jello, but they are not as stable as an enthusiast would like as the foundation for 5th Gen performance.

When your 5th Gen is on an alignment rack, the technician adjusts Caster, Camber and Toe to within a 10th or 100th of a degree. The OEM sub-frame bushes allow a much larger range in dynamic alignment angles. These changes in dynamic alignment account for the loose rear end, rear end step out or rear end steer. Filling the voids in the OEM sub-frame bushes reduces the range of dynamic alignment and loose rear end, rear end steer, and rear end step out go away. The rear sub-frame complete with IRS uses four bolts to attach to the monocoque. There is a locating tapered pilot that passes through the larger rear sub-frame bush and positions the sub-frame to the monocoque. The larger sub-frame bush has a ferule that fits over the Locating Post. This not only centers the sub-frame, but anchors it much as a weld would to the monocoque. The movement in the rear sub-frame is relative to the voids in the OEM rubber bushes. If the voids are filled with urethane inserts or the OE bushes replaced with higher durometer full urethane, movement of the rear sub-frame is virtually eliminated.

Rear Sub-Frame Rear Bush / Bolt / Locating Post

Rear Sub-Frame Forward Bush / Bolt Area

The ZETA II Camaro features much larger sub-frame bushes than the ZETA I G8. These were improved to handle the higher loads created by larger wheels and tires with the high RWHP found in the Camaro. While they are an improvement, we do not feel they are stable enough for the way we drive a Camaro so we designed three solutions.

Pedders EP1200 Sub-Frame Inserts are good up to 550 RWHP. The inserts fill the OEM voids in the rubber sub-frame bushes from both the top and bottom. The control surfaces are dramatically increased. Since the OEM bushes remain in place, this is more than just a great upgrade. It is relatively easy to install the EP1200. These eight pieces transform your Camaro and are probably the single biggest bang for the buck modification you can make.

When Chevrolet introduced the Convertible they also made a change to the sub-frame bushes to address rear-end-step-out. If your Camaro was built in 2011 chances are it has the revised sub-frame bushes. The revised OE bushes have a bit more rubber in them and less NVH void space. They are an improvement over the earlier versions, but we at Pedders still feel they could be better and advise the 5th Gen owner to start with the foundation, to start with the sub-frame bush inserts or full bushes. On the left are the voids in the FE3 sub-frame bush. On the right you can see that the small voids have been filled, but there is a lot of empty space to be filled.

While Chevrolet engineering has improved the original 5th Gen sub-frame bush design starting with the first convertible, the smaller forward sub-frame bush in the FE3, FE4, FE5 and FE6 all have voided space and only the pencil wide shoulder of the bush for control. On the ZL1 the smaller front bush was made of a harder denser rubber to improve control. They still left a lot of 'room' for improvement. Pedders EP1200 sub-frame bush inserts fill the room, the empty space and dramatically increase the the upper and lower control surfaces in the front, small OE sub-frame area.

The rear sub-frame OE bushes had the voids filled starting with the Vert as well. The rear sub-frame bush is the same in the FE4, FE5 and FE6 5th Gens. Look at the control surfaces and you make the decision. Which will offer more control?

OE Sub-Frame Bush

Pedderised with EP1200 Sub-Frame Inserts

The best part of this foundational upgrade is that they is absolutely no change in ride quality. NONE. What you do gain is stability in the IRS. Your Pedderised IRS is more stable and more predictable.

Pedders EP1200 inserts will require a trim to fit in the revised sub-frame bushes. In this photo you see the fingers on the inserts that fill very thin voids in 5th Gens built prior to late March.

To fit a Pedders EP1200 Insert Kit on a 5th Gen (some 11s, all 12s and 13s) with the revised bushes, use a pair of scissors to trim the very thin fingers off the inserts. In this photo, we have covered the fingers with white paper. As you can see, what remains 96% of the urethane material by weight to fill the voids that remain in the revised OE bushes.

With the increased grip of the ZL1 specifically compounded tires and the increase in power with the LSA the ZL1 and the denser front sub-frame bush we find the inserts to be a perfect match and suitable for use to 650 RWHP. Btw, I wonder where GM got the idea to fill in at least part of the void in the sub-frame bushes

For those taking all Camaros, with the exception of the ZL1, beyond 550 RWHP, drag racers and hard core corner lovers the Pedders EP1201 full urethane Sub-Frame Bushes. With these robust bushes installed and well over 550 RWHP your Camaro will launch cleanly and track true under load. In these photos you can almost feel the improvement in performance. The OEM ferules are designed for ease of assembly on an assembly line. The OEM ferule has 3/4" holes for a 14mm bolt. Those loose fitting for ease of assembly OEM ferules are replaced with Pedders and holes suited to the 14mm bolts used to more securely attach the sub-frame to the monocoque. This change means there is no possible movement in the assembly under any load that doesn't bend or shear a sub-frame bolt. The increase in control surface is nothing short of MASSIVE. Your rear sub-frame will now follow your Camaro and not attempt to steer your Camaro. Switch backs are tamed. Drag launches are harder and crisper with a more efficient transfer of power.

For ultimate in IRS control Pedders has developed the EP1201HD. Racers use Delrin bushes machined from stock. These are hard plastic suitable ONLY to a race car. They place too much load on the small welds throughout the sub-frame. Aluminum bushes are no different. Delrin and Aluminum are great in a race car where the welds are checked after every race weekend and the entire car is seam welded. In a street driven automobile there has to be some forgiveness in the sub-frame bush material to protect the useful life of the sub-frame and monocoque. Pedders EP1201HD is a urethane of high dura that when captured by the Camaro sheet metal performs like Delrin or aluminum right up to the point of accidental impact when there is just enough forgiveness to protect the key components. These bushes do transmit more road noise than the EP1200 inserts or the EP1201 full bushes. In the Pedders USA, LLC Camaro we barely notice a difference because the aggressive tires we run. The EP1201HD is not a typical Pedders bit. It is designed for ONLY the most dedicated enthusiasts. In the video, you will see that there is NO visible sub-frame movement, even with a 3 2 downshift with wide open throttle.

While the Pedders bushes appear to be larger in height than the OEM bushes. That is an illusion. The Pedders bushes are designed to fill the space between the sub-frame and the monocoque just like the OEM bush with no change in the size of the gap. On the lower portion, the Pedders bushes fill the metal OEM plates. There is a pre-load on the bushes, but no change in the installed height. We wanted achieve both control and long term durability of the sub-frame and monocoque goals with minimal change in OEM NVH and no change in ride quality and that is what the EP1200, EP1201 and EP1201HD deliver.

We used a prototype tool to remove the sub-frame bushes on the car. A plastic piece of 5" PVC pipe. Gorilla tape on the outside just in case. An old bearing plate for the bottom with another round steel disc from the assortment we use at the hydraulic press. A 14mm Acmes threaded rod with nuts and washers completed the 'tool'. A strong rattle gun (Aussie slang for Impact Gun) applied pressure along with a little heat to separate the paint from the FRP jackets and the bushes were out in minutes..

A quick look at the increased control surface data illustrates the benefits of Pedders inserts and bushes for the 5th Gen. In addition to the increased stability of the the IRS the larger control surface spreads the increased load over a larger area to preserver the integrity of your sub-frame.

All bushings are not created equal.

User / Owner Video


Putnam Park Danny Popp driving the Pedderised L/28.

What does all this mean to a 5th Gen Camaro owner in terms of suspension performance?

Pedders Camaro Running Race Car Speeds on Track

It means YOU own a bad XXX automobile. It means you own more car than you probably thought you had purchased. It means your Camaro will remain tight and solid for many years and thousands of miles. It means your Camaro will respond exceptionally well to suspension modifications because it is such a robust and stable platform. It means you can drive your 5th gen with confidence knowing that it is built by Chevrolet to exceed your expectations. It means your suspension will work as designed when driven to the aggressively on track or down your city's streets.

The 5th Gen Camaro off the showroom floor is a very good driving experience. You will notice that the ride is supple over bumps. This is due to the advanced design of the ZETA II chassis along with the very large wheel and tire package. There is substantial lean and roll, yet the 5th Gen sticks in turns. The steering is a bit softer than we would like. The SS Brembo brakes are very good, but the pedal feel not as sharp as we would like. Drive past 7/10ths, you'll find the IRS has too much movement. The range of dynamic alignment changes allows rear end step out, rear wheel steer, a loose feeling in the rear. It undermines driver confidence. Having said this, a bone stock 5th Gen Camaro blistered the Nurburing. On a scale of 1 to 10 with 10 being a perfect car, we rate the 5th Gen SS a 6.5. The SS 1LE is a 7.5. The ZL1 is an amazing 8.5 of the showroom floor.

Track Time
Nordschleife 7:41.27
Inde Motorsports 1:41.29
Ranch Config. 4 1:41.29
Laguna Seca 1:39.18
GingerMan 1:42.05
Grattan 1:27.95

As good as the ZL1 times are, and they are very good times, no street legal Camaro has matched the Camaro's Gingerman lap time.

Pedderised NASCAR Pace Car

How could it be better? If the 5th Gen SS were not built to a market price-point it would be close to a 10 off the showroom floor. Price-points are critical to sales so that is not the case. One straight forward example is Urethane. Urethane is far more expensive than rubber. The low hanging fruit for the Camaro owner is in urethane inserts for the radius and sub-frame bushes. Installing EP1200 inserts EP1201 Full Replacement Bushes or Pedders EP1201HD tack bushes settles down the IRS virtually eliminating unwanted rear end steer, rear end step out and the feeling of a loose rear end. These inserts work with the OE parts to make your driving experience more confident. The most any driver can hope for is their race car is stable and predictable. Addressing the sub-frame bushes and the associated rear end step out created by a wide dynamic range of alignment angle changes increases the stability and predictability of the 5th Gen Camaro. This isn't an optional up-grade. This is your first foundational 5th Gen upgrade and the building block for all future upgrades.

GM redesigned the radius arm on the ZETA II Camaro. It uses a large hydraulically damped bush on one end and a ball joint on the other. The arm is more linear to deliver improved steering feel. Drivers that are tuned into their Camaro will notice slight softness in steering feel, the brake pedal and perhaps describe it as isolated or vague. Pedders started early on with the Camaro GS Prototype built at the Milford Proving Grounds and worked on a full urethane radius / brake tension rod bush. This was a very special project with GM the 2010 Camaro GS Race Car Concept shown at SEMA 2010. This video walks you through the OE and Pedders bushes with Jason Debler from

Replacing the hydraulically damped OEM radius rod bushes will help with steering and pedal feel. While the NVH properties are excellent, they are too soft for performance driving in our opinion. Pedders offers three solutions for this. The first option is a direct replacement street-friendly urethane insert for the OEM rubber bit. The firmer urethane insert removes some of the compliance in the bush improving brake pedal and steering feel. The back-story on this bush is it is a GM designed part. One of the GS engineers wanted to test it for use in in sanctioned racing. We made twenty sets for him. Unfortunately that project was shut down during the GM adjustment period. The samples were sent back to along with permission to take them to market. Using an EP6578 is as simple as removing two bolts, removing the soft OEM rubber insert, installing the Pedders urethane and bolting it back together. You may wonder if such a small part can make a difference in such a large automobile. You will be pleasantly surprised on their first test drive.

The full urethane bush replacement is Pedders EP6577 Camaro Urethane Steel Jacketed Radius Rod Bush. This is one robust bush with holes and voids designed to make our street friendly urethane mimic the NVH characteristics of the OEM bush with the performance of a urethane bush. If you track your car, the EP6577 will be the most durable solution. The inserts work to reduce motion, but the basic issue of the OEM bush remains -- it is hydraulically damped and can potentially fail on track. Pedders EP6577 is virtually indestructible on or off the track.

The third is an EP6579 full face Camaro Front Extreme Radius Rod Bush Insert replacing the soft OEM rubber insert with a very high durometer piece. It was designed as an alternative to the EP6578 for the GS Camaro project. The combination of bonded rubber ferrule steel jacketed bush with a full face high durometer urethane insert is outstanding. This solution is extremely firm and may lead to premature wear in the tie rod ends or the steering rack. This is the solution we have installed on the Pedders USA Camaro because we prefer the extra control. We have clients with over 100,000 miles driven with the EP6579 and no signs of premature wear. Because we are Pedders we error on the side of caution, but in this case it appears we will be lifting the cautionary wording soon. This is a hardcore option for the most demanding driver and my choice for my 5th Gen.

These two short videos show you how to install the inserts. It is so easy, even a caveman could do it.

Removing the OEM Rubber Snubber

Installing the EP6579 Full Face Urethane Insert

All three Pedders radius / brake tension arm solution accomplish the same goal in a different way. They reduce the range of caster change while driving. The direct result is a more on center feel to the steering. Combine that with a Pedders Tight Spec Alignment and you'll drive away thinking a new steering rack was installed. With the mission critical required foundational bushes in place your 5th Gen is ready to go or ready to grow.

Last edited by JusticePete; 10-03-2013 at 09:50 PM. Reason: Updated Sub-Frame Bush Data
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