[Metallicat]

Ok, I AM going to order some H&R's in the very near future. Given the fact that I only have a basic hydraulic floor jack at my disposal, can I perform this installation myself? I am mostly worried about having enough room to work with under the car. Plus, are the springs easy to remove and install or is any type of spring tension relief tool required?

If I have a local shop install the springs, are there any questions that I should ask before having them installed? Do all of the bolts really need to be tightened with the car on the ground or can the springs be installed in the air without worrying about binding in the bushing department?

In other words, are these springs idiot-proof enough for me to install them in my driveway without any help other than my jack?

 

[waldo]

You absolutely should tighten the bolts with the car on the ground. There is a tremendous amount of bushing rate in the suspension and it can make a huge difference in the ride quality. Spring installation is exactly the same as the Mazda 6, there are a few good procedures on http://forum.mazda6club.com/. With just a jack it may be a bit much for you, since you have to compress the rear control arms to get the rears in and our (you'd need at least two jacks, one for the car and one for the arm). The front springs require a spring compressor since it is basically a strut, but you can borrow these from Autozone and others. Keep in mind that the alignment will change slightly with a drop as well, so you should plan on having that done a week or two after the install.

 

[Metallicat]

Thanks for the reply Waldo. Got another question. Why would the suspension bind if the bushings are tightened when the suspension is in the extended position as opposed to the compressed position? I know the bushings are soft, does this allow for lateral movement of the wheel? The upper and lower control arms should allow for a specific type of wheel movement when encountering a bump. How is that wheel movement compromised when tightening the bushings while the car in suspended in the air?

 

[waldo]

Think of a bushing as a torsion spring (just like a torsion bar on some 4x4 trucks). When you twist it, it has a spring rate, or resistance. What you want is a bushing that provides rate linearly in both directions. So you neutralize it at the "normal" driving position. That way when the suspension goes up, the bushing twists and acts like a spring. When the suspension goes down the bushing twists the other way and acts like a spring. If you tighten them with the suspension hanging down, then driving at normal position they will already be twisted, so when the suspension goes up, they will twist even more and have a higher rate (unlike a coil spring, the rate is not linear), giving a harsher ride. When the suspension goes down, the bushings will unwind, and actually push the suspension down faster, instead of helping slow it down. Plus driving around with them "pre-twisted" will increase their wear substantially.

 

[Metallicat]

Ah, that makes perfect sense now. Why do they use rubber bushings instead of solid bushings that are not subject to torsional, twisting loads? It seems like solid bushings would eliminate the spring effect of the rubber bushings and would provide better wheel alignment under heavy cornering situations.

 

[waldo]

It wouldn't be a solid "bushing", but rather a ball joint of some sort, These are used in some places, like on the Lincoln LS rear suspension, it has 3 ball joints in place of bushings. But ball joints are more expensive, like maybe $1-3 more each. Multiply that by about 12-16 per car and it's significant! Plus they don't offer any recessional compliance, so impacts become very hard. They also have inherent friction, so you loose a little bit of that gliding feel.
My RX7 has a hybrid ball joint/bushing, it's actually a ball joint with a rubber "jacket" that encapsulates it. Pretty interesting compromise, but now at 60,000 miles I have to replace all 6 of them at about $50 each!