has anyone used the Poly Bushing kit on an '07 as i am thinking of going for the American Muscle Kit from prothane but want to make sure I am doing the right thing. I have heard they are not as good as rubber as well as I have heard they are better then rubber.
Any thoughts or experiences?

 

In summary, the are better for handling, but may affect ride and require more maintenance in the form of greasing.

 

^ not necessarily

pillati.... Are you talking about ***THIS*** kit? If for the LCA's and UCA, a spherical end on each of them would be an improvement over OEM rubber or aftermarket poly. This is not as big a deal as on the pre-S197 rides, but you will introduce a bit more suspension bind via 100% poly bushings on the control arms out back.

What are the ULTIMATE goals for your ride?

Jazzer

 

YES that is the kit I am looking at. Currently there is a clunking (knock) when I hit small bumps so I just figure it is time to replace the original bushings so was thinking of the poly over rubber. I am a spirited driver, fast off the line and love the corners. What do you mean by "suspension bind"? As this is a daily driver with 66k but I try not to use it in the rain/snow unless i have to.

 

Suspension bind is any part of the suspension that has "resisted" mobility due to forces OTHER than spring rate, shocks/struts and/or sway bars. While this refers mostly to the rear suspension, some of the front sway bar mounts are problematic in the following way as well. I am not as familiar with the S197, but the earlier models were bad in this way too.

The reason that the OEM bushings are rubber is two-fold. The first is to limit noise transmitted into the cabin (NVH). The second is the "give" they provide upon things like rear axle articulation (one wheel up in the well, while the other is way out). During this action, the LCA's and UCA' must twist laterally, as they are connected to both the moving axle and the stationary body of your car. The OEM bushings are soft enough to allow such articulation relatively freely. Replace those rubber with poly and you have MUCH less compliance in all directions. On one hand, you have less "slop" in the connecting parts, so your car is more responsive to input (be it driver or road conditions) and funner to drive, IMO. The negative side is additional NVH (Noise Vibration Harshness) and resistance to free articulation of the axle becomes more limited. The MUCH better, albeit more hardcore way, is to install a Heim joint on at least one end of each of the rear control arms. Now, this is WAY more than most need on a street car, but I happen to think that a mechanically sound connection is beneficial over the alternatives regardless of the conditions in which one drives.

I am not necessarily suggesting you install Heim joints on your ride, just that I am not a fan of stiff bushings where compliance is needed for improved suspension performance. I tend to be much more hardcore on the subject of suspension and certainly some alternate points of view you should consider prior to blindly following some crazy Cat on the interwebz

Jazzer

 

I think what you really want given that both cornering and traction for street driving are indicated is LCAs with some sort of poly/spherical combination. I think UMI has an offering - check out stranoparts.com and maybe give Sam a phone call to discuss. There is also a 'hotpart' version which may be durable enough for street use even though there are reports that it isn't enough for serious road course track day purposes. There are other sources, I'm just typing off the top of my head here.

Most poly/poly-bushed rear suspension arms should be considered street/strip parts, or maybe strip/street, at least in their out-of-the-box condition. Driven mildly to moderately on the street, most people are fine. Driven hard enough for much slip angle at the tires to be developed and they may not be as nice.

Poly-bushed LCAs are pretty good as far as dealing with wheel hop is concerned, but as Jazzer has already indicated they'll also introduce some extra rear suspension stiffness, aka "bind" (which tends to "loosen" the handling in a manner just like swapping in a bigger rear sta-bar or stiffer rear springs would except that the amount of added bushing stiffness isn't generally known and may not remain constant). It's one thing to take a little of the S197's understeer out, but it is entirely possible to overdo it. Keep in mind that you'll still have to drive through wet corners from time to time, so a "dry" race setup as far as understeer/oversteer balance is concerned might not be the hot tip for relaxed everyday driving.

The additional roll stiffness coming from poly/poly LCAs may make the car corner enough flatter to notice, but keep in mind that "flatter" does not necessarily mean "better". The S197 doesn't understeer all that badly, and it doesn't roll all that much. If you want flatter, do it the right way with stiffer springs and bars.

I can tell you from direct experience that poly at both ends of just the LCAs will also toss your head from side to side a lot more over driveway entrances and when crossing drain gutters at an angle. I'd tell you the mod that takes a lot of that out, but you might as well do it the right way by getting the better LCAs the first time instead of band-aiding a second-rate solution.


Norm