hapnermw

I've had Pfadt poly bushings installed on my C6Z for about two years (I greased and installed them myself). They replaced a set of VB&P poly bushings I had gotten installed a year previous that were a squeak-fest. The car has a set of Hardbar Penske triple coilovers with dual hypercoil springs and spherical bearings (pfadt poly bushings on lower rear), Hardbar camber plates, Hardbar upper arm stud kit, stock sway bars and bushings; and Nitto Invo street tires. Ride height is close to stock for max suspension travel.

My primary reason for making the switch to sphericals was that I suspected the poly bushings were binding and I wasn't getting the full benefit from my coilover investment. Since the coilovers had replaced six rubber bushings with sphericals and this had not been an NVH issue, I was guessing that removing the rest would be livable. I had been getting a bit of sound over some bumps but nothing like the constant squeaking of the VB&Ps.

I was interested to see what the state of the poly bushings were after two years and 12+ track days. They were all in good shape - none were distorted or worn in any obvious way. All of the lower bushings, including the rear shock bushings, were binding. By binding I mean that the centers could not be driven out of the bushing - they could only be removed once the bushing had been extracted. Several of the front upper bushings were partially binding - with some effort I could remove the centers and the rest (four rears and one front) slid smoothly out.

Two things complicated the installation of the sphericals. I did not want to interference fit them - I wanted to be able to remove them later if needed which is possible by breaking the locktight with heat as long as the bearings themselves are slip fit. Many of them could be slip fit with a small amount of coarse emery of the arms; others (about 6 - 3/side) required up to an hour each of hand emery to slip fit. The second install issue is the fit of the lower sphericals into the frame is tight and metal-to-metal does not make for ease of insertion - I had time to develop an intimate relationship with each frame-bearing mating . Overall, the kit seemed to be very well engineered.

I'm pleased with the results. The improvement is obvious. The ride is actually smoother. You can feel the car eating the bumps - prior, the bumps upset the car more. There is more road vibration coming through. You can feel more road detail in the wheel. So far, I'm pleased with the NVH tradeoff - I drive this car daily. It is my feeling that, overall, the poly bushing NVH was actually worse than the sphericals. It is great to see the tires 'stick' to the ground as the car is jacked. Handling seems to be much smoother - the weight seems to transfer more smoothly.

If you can afford the sphericals they are a cheap way to substantially improve the suspension - don't let the track-only tag scare you away. If you are thinking about poly bushings you might want to reconsider - a binding suspension may be worse than a somewhat sloppy stock suspension.

Zenak

noise with the sphericals? harsh ride change?

Im putting in my pfadt polys in the next week or so.

To avoid that binding issue getting them zerk fit for chronic regreasing.

thanks :-)

gkmccready

Let us know about on-going maintenance. I imagine you'll be spraying lube on these all the time to rinse the dirt out? Not that you weren't having to lube the poly all the time, anyway...

dfinke23

I thought they were sealed.

hapnermw

The bearings are sealed. There is space between the bearing spindle and the outer rim that could accumulate dirt but it should be easy to spray this out when changing between street and track tires.

hapnermw

Don't waste your time with zerks.

The folks who installed my original VB&P bushings installed zerks in each A arm bushing surround. They should have known this made no sense and at the time I didn't realize what the actual issues with poly bushing binding were.

Poly bushings need lub at their ID to keep the bushing centers from binding - injecting lub at the bushing OD/A arm interface does nothing but make a mess.

The only way to lub a poly bushing is to remove the aluminum center and relube its ID. Plan on doing this frequently or keep the stock bushings.

geerookie

This is it exactly!
Spherical would be great but for the street they have another problem. With the limited travel of the control arms they tend towear divots in the bearing race which cause another set of problems. Bearing are designed to rotate 360 degrees and will cause even wear that way. When used in suspension they don't fully rotate and therefore accelerate wear. But, they do work WAaaaaayyyy better than Poly.

I wish a vendor would come up with an intermediate solution, say Delrin!
Hint Hint.

hapnermw

Yes, this is a potential weakness of sphericals used in suspensions; however, I'm not sure that delrin is actually a better solution.

I'll let ghoffman comment on whether his spherical upper shock mounts will last longer/perform better than the delrin pin top shock mount he recently created. I've been using the spherical upper mounts for 14 months and they seem to be in perfect shape and their movement is even more restricted than the A arms.

I now have 28 spherical bearings in my suspension. The four in my Baer end links have been installed for three years. No issues yet.

The folks from Pfadt said that the sphericals lasted a racing season on the Callaway C6 GT4 cars in europe. That they have not heard of anyone else wearing out a bearing.

ghoffman

I am not sure what will last longer, nobody has failed either the monoball and clevis or the Delrin pin top mounts yet.

VetteDrmr

Slight hijack: I'm going to be building up an LS-1 Miata and need to replace the stock, dead bushings. About the only way to replace these with poly, unless I want to spend as much on control arms as I did on the car.

So, I was thinking about cutting a small slot along the ID of the bushings and install zerk fittings to work some lube into the ID area.

Is there something I'm missing?

Thanks, and have a good one,
Mike

dbratten

I added zerks to mine when I installed the polys but I drilled through the poly after installed to allow grease to flow onto the pin in the middle. I also added a roll pin to retain the poly bushing to keep it from rotating in the arm. It's working so far.

--Dan

John Shiels

bushings on heavy equipment have channels or grooves cut into them

geerookie

OK, but how about Delrin vs. Poly vs. Spherical for pivot points in the suspension? i.e. control arms

ghoffman

Well, the poly just has binding and friction issues, no matter what, but has some compliance which is good for NVH. When new, clean and tight, the spherical bearings have very low friction, very low deflection, but do require more maintenance and are expensive. This is especially true on the LCA's where they are subject to more water, salt and dirt. On our shock mounts, even the lower "T" bar has very good durability, but we use stainless steel everything there, even the snap rings and washers. The Delrin has very low compliance, probably not as stiff as the bearings (seems like it would for sure, but it depends on the specific setup) , but way stiffer than the poly with very low friction on par with the spherical bearings, but no lube or maintenance hassles. The price is 1/2 way between the poly or sphericals.

Life is one big trade study, huh?

hapnermw

It would have been nice to have had a delrin option - I had been waiting around for one but I could no longer put up with binding poly bushings. It seems that the main issue with sphericals is the price.

It's strange that so much is made about loss of NVH with sphericals. This might be an issue in comparison with factory bushings but it isn't in comparison with poly bushings.

Pfadt does not list the materials used in its spherical kit so it is hard to predict how they will handle the LCA environment. My hope is that periodic power washing will be sufficient to keep them clean. The LCA bearing spindles leave enough open space to make washing out the area around the bearing itself easy.

The effort you put into engineering your lower T bar spherical shock mount and the fact that you publicly disclose its materials is an example other vendors should take note of.

ajg1915

Robert at SpeedSouth offers the zert fitting install.

The newly designed Pfadt Bushings are halfed and the zert fitting is placed in between the split so that the inner center shaft is what gets lubed.

Additionally the new Pfadt Bushings have groves and the inner shafts have been especially coated to reduce friction.

When I get my parts back from SpeedSouth I 'll post up some pictures.

hapnermw

The VB&P bushings I had originally installed were also split but the grease did not get through the split to the center - it just came out the sides. Design-wise, split bushings are for simplifying installation and likely don't have any impact on lubrication.

The version of the pfadt bushings I installed did have some small inner grooves for retaining grease. Possibly the current version with anodized centers will reduce binding.

Someone else mentioned drilling the bushings and then pinning them to the control arm to keep the hole under the zerk fitting. This might work.

The bottom line is the bushings are theoretically designed to provide bind-free performance for some reasonable length of time; however, it is not clear that they do. The binding properties of the bushing material just can't be overcome for very long. If they worked as designed there would be no need to come up with various Rube Goldberg lubrication strategies that may or may not keep them from binding.

Since my binding LCA bushings did not squeak to any extent, there are likely others in the same situation. It appears the only way to tell for sure is to remove the control arms from the frame and see if the centers are binding.

ghoffman

Noise, or rather the lack thereof, does not indicate that there is no binding. I did this test on the upper front, but the problem is more acute in the lowers.

L98Terror

OK everyone to get the point across or how much binding there actual is listen from :30-:32 with your eyes closed

ghoffman

Ok, ok, perhaps too much drama there, but poly does bind even when there is no noise of any kind.