Blair

I am pretty happy with the handling balance of my car the way it is set up now. I am still using the stock LCAs and UCA. I am thinking of switching to an adjustable UCA and adjustable LCAs with spherical bearings to adjust the pinion angle after adding the driveshaft. I noticed that the stock bushings offer quite a bit of resistance to movement in the back when you unbolt the shocks and remove the rear springs, they actually hold the weight of the axle up when it is supported only by the bushings. If i switch to the spherical bearings is that going to mess up my current wheel rate on the rear axle because of the freedom of motion in the spherical bearings?

DRock

Do not go spherical bearing on both sides of the LCA's. They can become very loud inside the car and will get anoying quickly. The poly/rod end set up is nice if you are looking for better articulation. That is what i run and i am 100% satisfied with what i have. There is a little noise increase but if you turn up the radio or roll down the windows you would never know. I do not see it messing anything up either though.

Norm Peterson

To answer the wheel rate question - yes.

OE-style bushings do affect the wheel rate in both two wheel bump and roll. It's due to the stiffness of the rubber and the fact that it is bonded to both its outer shell and the inner sleeve, hence any motion of the suspension requires distortion of the rubber. It's probably a 5% - 10% effect, so you might not notice.

Poly doesn't add much rate in two wheel bump mode, but can add a rather large amount in roll depending on the details of the LCA and the poly itself. The added roll rate WILL affect handling balance, which is the main reason for getting rear control arms with the poly/rod end combination (the rod end removes most of the poly's added roll stiffness).

Worst case where you do notice and it bothers you enough to have to do something, rear spring and sta-bar stiffnesses could be increased by a bit of swapping or adjusting.


Norm

Blair

A 5% to 10% reduction doesn't sound too bad and I imagine the majority of that loss would be at the extreme ends of articulation. I'm very happy with the handling now, I am just reluctant to add the adjustable control arms if that is going to mess up my current balance significantly. But it sounds like it won't. I am getting a little vibration on decel since adding the aluminum driveshaft. I'm hoping that the less compliant UCA and maybe a little reduction in pinion angle will help get rid of that.

Red06

Blair,

Were you going to poly / spherical combo or rod / rod on your control arms? if you go to the poly/ spherical, you shouldn't notice too much difference. The poly bushings are more resistant to movement than stock and the rod ends are (much) less resistant to movement. Adjustable shocks can help smooth out any issues you may have. Unless your car is a track toy (not a daily driver) i wouldn't recommend rod /rod control arms due to the significant amount of road noise transferred into the car.

I have the poly / spherical combo and really like the result. If i had it to do over again, i'd put the rod end at the differential rather than at the body on my UCA. The only issue with poly bushings is that over time they will make noise (creak). Be sure the control arms you buy have grease fittings and you buy some good silicone (not petroleum) grease.

There is no reason to have an adjustable upper and lower control arms. Pick either the upper or lower to be adjustable. Adjustable uppers are a pain to mess with but you should only have to adjust it once. lowers are easier to adjust but you need to be sure you keep the axle perpendicular to the car.

I run closer to -1 degrees than -1.5 for my pinion angle with my aluminum drive shaft and the poly / spherical control arms. I haven't had any vibration issues up to 135 mph.