WHT Z06 Mods: Delrin bushings

WHT Z06 Modifications:
Delrin bushings

Borg Motorsports

Control arm bushings

At about 80K miles I started noticing some signs that my control arm bushings were wearing. For example, cracks in the road could cause the car to pull one way or the other. In the past I've taken this as a sign that bushings are worn out and allow too much movement. I've heard this condition described as "dynamic toe" and it can be pretty annoying. I've installed polyurethane bushing kits on numerous other vehicles so I decided to do that. Based on previous experience I initially tried Energy Suspension again. However their C6 Corvette kits do not fit a Z06; at the time, none of their sellers and only some Energy Suspension technical support members knew this!

The difference between the base vs. Z06 is in the rear upper control arm attachment to the frame. For the base, the arms fit into frame and a bolt secures each bushing. The Z06 rear upper is like the front in that there are dogbones held in place with bolts that thread into the frame. The difference is likely because the base frame is steel and the Z06 frame is aluminum.

Unable to find any polyurethane bushings I investigated Delrin. I found three options: Ridetech, Van Steel, and Borg Motorsports.

Of these only Borg Motorsports offers Delrin AF100 which contains 20% Teflon (PTFE) fibers which lubricates as it wears. Standard Delrin is expensive but the AF100 version is even more so.


Delrin AF100 Kit	Upper Control Arm

More than half of the labor of installing polyurethane bushings is in removing the old molded rubber from the old hardware; and with its independent rear suspension the C6 Corvette is twice as much work than with my old SS Camaro. A nice feature of the Delrin kits is that all new hardware is provided; this saves a lot of labor.

Remember that you'll definitely need an alignment when you're done. And if your motor and transmission mounts are old now would be a good time to replace them.

Impressions

Replacing my control arm bushings definitely solved my "dynamic toe" issue. A C6 Z06 (which does not come with magnetic ride control) already has a fairly harsh ride. The main difference I have noticed in the ride is when going over small rocks, road reflectors, and draw bridge transitions, But it didn't take long to get used to this and the car feels a lot more stable when taking sweepers. So I think this upgrade was worth the labor and expense.

Squeaks

About 2500 miles after installation I started hearing squeaks from the rear control arms. This was due to manufacturing variations in the bores in the rear upper control arms. My bores were a little bit larger than spec which allowed the bushings to rotate freely. This is extremely rare but seen before. I took the control arms out, carefully measured all the bores, and Borg sent me a new set of bushings which I installed.

About 4000 miles after installation I started hearing squeaks from the right front. I meansured them and they were all "within spec". Ultimately I disassembled the right front upper, buttered the bushings up with some Energy Suspension grease, and put it back together.

About 4000 miles after installing the new rear upper bushings I started to hear some minor squeaks. If this gets worse I'll probably take them apart and grease up the bushings.

Installation Notes

Separating rear lower ball joints can be tricky on C5 and C6 Corvettes. The threaded shaft on the ball joint has a hex recess in its end but there is not very much room above it to hold the shaft with a hex key while loosening or tightening the nut. The Kent Moore J-42188-B comes with a special hex tool that solves these issues.

Kent Moore J-42188-B
I used an OTC 7503 "outer tie rod remover" to separate the upper ball joints:

OTC 7503

When there's room to use it, it's an amazing tool; as the website says, "up to 5 tons of force can be applied." It seems like you barely get it in place when the ball joint pops.
One way to remove and install control arm bushings is with a shop press. Since I don't have one (and really don't have room in my garage for one) I got an OTC 7249 "Ball Joint Service Kit."

OTC 7249 Bushing Removal

Once setup an electric impact makes fast work of bushing removal.
Ridetech makes a very nice tool for removing lower control bushings. It works well with either a shop press or a control arm bushing tool.

Ridetech 85000006
I used Knipex 46 21 A11 Circlip Pliers to install the snap rings.
The factory service manual says you need to remove the transverse springs when removing the front and rear lower control arms. I found that I could support each arm with a bottle jack while separating the lower ball joint and then ease it down. I never found that the springs put much force on the arms.
Given the squeak issues I experienced, I recommend using some quality high-temperature grease (e.g. Engery Suspension) on all bushings during installation.


OTC 7249	Bushing Removal