My car is a 2002 BMW 330Ci Convertible. Yours may be the same or slightly different.
The function of the Lower Control Arms (LCAs) is to hold the wheel in position while allowing it to move up and down following the uneven surface of the road. BMW designed the LCAs to soften the impact of rough roads and harsh acceleration/deceleration. This is accomplished by the LCA bushing, which is filled with fluid apparently.
Unfortunately the LCA bushing can become too soft over time. Mine started around 50K miles. If they are not replaced, the LCA will put too much stress on the ball joint's nylon lining, causing it to fail (developing a play), which leads to uneven wear on the tire and poor handling. In order to replace the ball joint, one usually has to replace the entire LCA, as the ball joint is pressed into it, which requires a power press and removing the LCA from the car. And, LCAs have to be replaced by the pair, which becomes expensive. What it means is that worn LCA bushings should be replaced in time.
Fortunately replacing the LCA bushing is not difficult, and there is no need to remove the LCA from the car. This is written for people who do their car repairs in their own garage, i.e., without access to a lift or specialized tools. My BMW dealer wants $500 for this job, so I decided to do it myself, given this economy. :-)
0. Buy a pair of lower control arm bushings. Mine were Meyle, which I got from Bavarian Autosport for about $100.
1. The most important part is putting the car on stands. On this car, it's not as easy as one would think because there is so little clearance between the frame and the ground. Doing this part correctly is critical to safety, since you'll be working under the car. DO NOT LET THE CAR FALL ON YOU! You'll be hurt seriously, I mean, killed, if 3,600 lbs fall on top of you. Make sure you're on a level and solid surface, like the slab of your garage.
1a. Apply hand brake, and put the transmission in the 1st gear. Choke the rear wheels.
1b. On this car, one cannot simply jack up the side skirt -- there are only 4 jack points that can support the car's weight. Instead, use the jack provided with the car (stored in the trunk) and lift one side of the front just high enough so that you can see the under side of the car and can slide in a hydraulic jack. Find the frame rail (marked by red brush) that runs along the bottom, about one foot from the side skirt.
1c. Use the hydraulic jack under the frame rail to raise the car enough so that you can put a stand to replace the car jack. Make sure you use a stand that can hold the plastic jack point securely. The photo shows the wrong kind of stand. You want to use a stand whose top is shaped like a Y.
1d. Repeat Steps 1b and 1c for the other side. Now you have two stands holding the front up. Because the car has very little clearance (about 4 inches) to begin with, you may need to raise the height of each side alternately and in steps to keep the stands straight.
1e. Jack up the back of the car on the brace (circled in red) just in front of the differential (but NOT on the differential). Again, you may need to use the car's jack to lift one of the back corners to slide in a hydraulic jack. Once you lift the back side of the car, you can use two more stands to support the car. Now you have the car on 4 stands. Rock the car back and forth to make sure it's sitting on the 4 stands securely. No, the car shouldn't fall from the rocking. If it does fall, it's still a thousand times better when you're not under it.
2. Looking at the under side of the car, you'll see the black plastic guard and the big aluminum brace piece (circled with red). You'll need to remove them in order to gain access to the control arm bushings. The plastic guard is held by several screws and 3 retaining nylon clip. The aluminum brace is also easy to remove by undoing the 8 screws (16mm).
3. Once the aluminum brace is removed, there is easy access to the lower control arm bushings. Notice that I put 4 extra stands under the car so that I would feel safer getting under the car. I also considered cinder blocks and lumber.
4. Here is a closer look at the bushing. Remove the two screws (16mm) holding the bushing to the car's frame.
5. Use a puller to remove the old bushing from the lower control arm. I have a puller as shown in the photo, but it didn't work because the hook kept losing its grip as I turned the bolt. Eventually a C-clamp worked. Make sure you wear protective eyewear -- the rubber can store some energy as you turn the puller or C-clamp -- you don't want anything to pop off and hit your eye.
Update: I finally got a picture of using the C-clamp:
6. Here is the end of the lower control arm after the bushing has been removed.
7. Putting the new bushing onto the control arm turned out to be a bigger challenge. I had seen a YouTube video where they simply hammered in an after-market bushing, but it didn't work for me at all because the rubber absorbed all the impact. Using my bare hands, I could push the bushing in about halfway. Eventually I used a steel strip together with the puller to press the bushing into the control arm. Also make sure you wear protective eyewear.
Update: it turns out using some soap eases this part tremendously. You can almost push the bushing in with your bare hands, and it's easily hammered in with a rubber mallet.
8. Attach the bushing back onto the car's frame.
9. Repeat Steps 4 to 8 for the other bushing.
10. Put the car back down on its wheels in the reverse order of putting it on stands.