Glad nothing's wrong with it! C4s definitely ride hard. Sometimes I'll saw the wheel real hard at 20-30mph (in a safe place to do so, of course) when I have a passenger, and their reaction always cracks me up.

I'd be interested about those new bushings. I wonder if they're just a lower durometer polyurethane, although I'd think if that were possible we'd already have them. I didn't notice a difference in ride harshness when I changed to poly, but something closer to rubber might quiet down some of the squeaks.

 

You know, mine does not ride that hard, really none of them, the two times I had problems was a splintered rear spring on my 87 and the front spring splintered on my 96. If your spring is splintered at all, time to replace, still betting that is the issue. They don't break in two and can be aligned with a splintered spring.

 

The new bushings being discussed are the Super Pro line from Australia. They are urethane, but much more compliant urethane than we typically see. It's a much better product for the rear suspension.

A broken or splintered spring couldn't cause a rough ride unless it let the car sag so low that it was down on the bump stops. If anything, the car would ride smoother because of the reduced spring rate.

 

Interesting. I was wondering how SuperPro durometer compares to, say, Energy Suspension, but it looks like there's a little more to it. According to this link, SuperPro bushings are a composite design combining polyurethane with an elastomer called polyelast. That seems like it could be a really good compromise depending on the longevity of the design. Edit: never mind, that's just for some diff bushings. And SuperPro bushings are quite a bit more expensive. The Energy Suspension kit for my car is $300, whereas just the bushings for the front control arms would be $320 through SuperPro. SuperPro doesn't offer a few things that come in the Energy kit, but the rest that they offer add to ~$480 total.

I still need to do my batwing bushings, but a regular poly bushing might be better there because of the limited motion (I think?) compared to most suspension bushings.

 

Without doubt, 100% certain, been there done that, a splintered spring will knock a filling out of your teeth!

 

Based on the composite dog bones visible in the pic I'm guessing your car is a '96? Can I ask where you found poly bushings to fit the composite bones? When I did mine they were not available, only for the cast aluminum ones.....
Thanks!

 

The thing is that for the rear suspension links, regular poly is too stiff and doesn't allow the off-axis movement that the trailing arms and camber rods have to negotiate when the suspension moves. Spherical joints are great here, but expensive and prone to some wear. Stock rubber bushings aren't available anymore. So SuperPro is the best choice unless you're really going for autocross or track performance. For the batwing, poly won't cause any problems but will make the ride a bit stiffer (not a lot).

 

Update:

I installed a new leaf spring. I opted to go with the #218 FE1 spring. My car came with that or so it says it did. The ride is noticeably better. It is still firm like it should be and you can feel every crack in the road but it's not so bouncy. It used to be like riding in a minitruck. Also it feels as though the rear is more firmly planted on the ground. With the old spring it felt like I could snap the back end loose anytime. Now it takes effort to get the back tires loose.

The install was very easy. About 45 minutes total.

Then I decided to take out all of the none adjustable rear end pieces that had newly installed Poly bushings on them and re-grease them. I didn't have anymore of the grease from the company where I bought the suspension kit but it says on their website Marine grease is a good substitute. Typical grease doesn't stick to polyurethane and will easily go away after some drive time. The Marine grease is much more sticky like the stuff that came with the kit. I got some and applied it very liberally on the parts. The suspension is now totally quiet. It's like a different car.

The spring was not a cheap part at $519 through Ecklers and the shipping was killer too at $132. But the code took off 10% so that helps. Even at that price I am happy with the results and makes the car much more enjoyable.


New Spring on the bottom.

The original spring is way wider than the new one. The old one also had a split on the bottom. It doesn't go all the way through the sping.

 

Your old spring looks damaged, and it appears to have been a much softer rate than the new one, judging from its thickness and much greater arch. So you may have been hitting the bump stops with it, and the new one is doing a better job keeping you off of them. At any rate, I'm glad you got a fix.

I don't think I caught that you had also done the batwing bushings in urethane. That alone will definitely increase the ride harshness over the stock rubber. It will also transmit more noises from the rear gears and diff. For others reading this post in the future, and for whom ride quality and street driving is important, I would not advise using regular stiff poly bushings in the rear suspension of a C4. If your stock rubber bushings really need to be replaced, then I'd suggest using the SuperPro parts. They are more compliant and easier to install and will retain closer-to-stock ride quality. They will also keep bind (non-linear wheel rates) to a minimum, for more stable handling.

 

One of the stock batwing bushings was rotted out pretty bad so I had to change them out. Re-applying the grease on the parts like I did has made a huge difference in the noises coming out of the back end. Especially on the control arms. Those connect right behind the door and if they squeak or groan it's right in your ear.