Shock absorbers are an often-overlooked maintenance point for our vehicles. This is unfortunate, as worn shocks not only make the ride less comfortable, but can effect handling, fuel economy and wear-and-tear on other suspension components. They're also relatively inexpensive and easy to replace, making them a very worthwhile do-it-yourself task for those of us who enjoy quality time under our vehicles.
Many of us learned at a young age that a good way of testing shock absorbers is to bounce a vehicle's fender up and down. When you release, if the fender returns to its original position after a single travel of the suspension, the shock was OK; if it continued to bounce up and down a little, this was a sign the shock probably needed replacement.
This isn't a bad rule of thumb, but it has some limitations. While the "bounce test" may work on passenger cars, most of our trucks are so heavily sprung that we can't bounce it heavily enough to load the spring to the point where the fender will continue to bounce. Secondly, while this test can uncover a really dead shock absorber, it may not reveal a shock that still has some life, but can't perform well under heavy usage.
With this in mind, I decided to replace the shocks on my F-150. The truck has about 54,000 miles on it, which is well past the mileage that many people report getting out of their OEM shocks. I also did notice that my truck seemed to "balloon" a little when taking turns at speeds over a snail's pace. Besides, I'm 46 years old and have never replaced shock absorbers myself, so I decided to undertake this little garage-based rite of male passage.
Selecting replacement shocks
There are many good brands of shock absorbers available in the aftermarket world. After a bit of evaluation, I chose Bilstein for a few reasons:
they have enjoyed an excellent reputation for many, many years.
their marketing emphasizes the technical reasons their products should be considered, rather than engaging in a lot of empty hype
they have an excellent web site, with an up-to-date application guide, product selection assistance, and contact information. I can't for the life of me understand how so many companies expect people to buy their products when their web presence makes their companies seem like a cross between a fortress and the NSA.
In theory, shock replacement is fairly straightforward: unfasten the old shock at top and at bottom, remove, and reverse the steps to install the new shock. In practice, a number of factors can make this a little more difficult. The primary determinant in how easy this project is, is how much room you have to work. For the most part, my F-150 had ample room, and the job wasn't too tough. Exceptions are noted below.
The front shocks
Removing the front shocks is pretty simple. The bottom of the shock is simply held in place with a nut and bolt; removing these was so easy, I didn't even bother to take a photo of it. The top is a little trickier: the shock is held in by a nut that tightens over the shock rod, but simply turning this nut will cause the rod to turn in the shock chamber, and the nut won't loosen. It's necessary to hold the rod still while tightening the fastening nut. In the case of my OEM shocks, there was a small nut welded to the rod below where it mounts to the vehicle.
This photo shows an open-end wrench holding this hold-down nut, while I remove the fastening nut with a socket. The open-end wrench is sort of hiding in the photo, so I indicated it with the yellow arrow.
Tightening the top nut on the front Bilstein shocks is a little tricky. To begin with, when I went to tighten the fastening nut, I discovered that there were no threads showing on the top of the rod sticking through all the mounting hardware. I made a quick call to the technical support department, who informed me that the solution was to compress the lower bushing so that more threads poke through. The easiest way to compress this bushing is to re-install the wheel and lower the vehicle from the jack, which is admittedly a bit of a hassle, but not unreasonable for a service operation that one only does every few years or so. Once I compressed the lower bushing enough to reveal threads, I hand-tightened the fastening nut, removed the wheel again (to give me working room) and tightened the fastening nut completely.
Torquing the fastening nut is also a little problematic. Bilstein's method of holding the rod still calls for inserting a 6mm Allen wrench into the top of the rod. While this was easy enough to do, it meant that I couldn't use a socket wrench to tighten the fastening nut. It also means that I couldn't use a torque wrench on it while tightening. Another call to technical support informed me that tightening until the upper bushing spread about 1mm beyond the washer would give an appropriate amount of torque. Not the most precise method in the world, but given the surprisingly low torque levels specified for this nut, I decided I could live with it.
The rear shocks
Installation of the rear shocks was a little more involved than the fronts, but still was pretty simple. Removing the lower bolts was a breeze, as there is tons of room to swing a wrench down here:
The tops are another story. The tops of the shocks come quite close to the underside of the bed, and the overall tight fit meant that I was turning the wrenches 45 degrees or so at a time. Here's a photo of the top of the rear passenger shock. Note the limited space between the top of the rod and the underside of the bed. This precluded the use of a deep socket, which was inconvenient, but no major deal.
The driver's side rear shock had its own challenge on top, too. While there was ample space above the top mount, there was very little around it. I had to slip a socket wrench between the frame and the underside of the bed to get at it. The hold-down nut was accessed through a hole in the frame (indicated by the arrow), which I can only assume is there for this very purpose.
The Bilstein rear shocks are shipped with the rods fully compressed into the shock cylinder. Once the wrapping is removed, the shock quickly expands to its full length, which is about 8" longer than the installed length. (There may have been some clever way to install while the shock was still compressed, but I couldn't figure it out.) The only way to install them was to put the tops in first, then compress them from the bottom until they fit into their mounting brackets.
This photo is of the rear passenger shock installed on top. There was barely enough room to get the Allen wrench into the top of the rod, and not much room for tightening the fastening nut.
Once the top of the shock was secure, I went about compressing the shock enough to fit it into its rear mount. I tried the time-proven technique of brute force and awkwardness, which yielded the usual result: no success and sore muscles. The shocks are just too stiff for me to compress that far (about 8" is needed, and I could only muscle them about half that distance). I slipped my floor jack under the lower end of the shock and applied pressure slowly and in small increments, stopping to reposition the jack to keep the shock near its mounting point. Once I got the shock to the right length for mounting, I used a pry bar to push it off the jack and into the mounting point, and a long center punch through the mounting hole to finish positioning it for the bolt. I'm honestly not sure how I would have done this without a jack, but I guess without the jack, I couldn't have gotten the wheels off in the first place, so we can consider a floor jack an essential tool for this project.
With the bottoms in place, I put the wheels back on and let the truck off the jack stands. Time for a road test!
I really wasn't sure what to expect from this project; while I knew that Bilstein shocks were certainly better than whatever the OEM shocks were, it wasn't clear to me how the higher quality might manifest during driving. The first thing I noticed was the truck felt a little "tighter" coming out of the driveway; somehow I felt less insulated from the road...and I mean this as a good thing. When I came to my first stop, I noticed that the front end didn't seem to dive into the stop anymore; more evidence that my old shocks were probably shot.
The real difference, however, came when I got onto a slightly twisty road. The truck felt, well, less "truck-like." I felt considerably more in control of the vehicle, which remained flatter in the curves and just felt better-connected to the road. It's not my intention to sling the truck into and out of sharp corners, but it's definitely nice to know it can take it if I do. It was really amazing to me what a difference a set of shocks can make; I honestly thought it would take more ambitious suspension modifications to yield the results I got.
One thing that Bilsteins are known for is a quieter ride. I decided to put this to a test, since I have a Lutron sound meter in my tool collection. I did some "before and after" measurements under as nearly identical circumstances as possible:
all windows up
sound system completely off
vents closed and the fan off
same roadways for before and after
Here's a summary of my readings (all data expressed in dB):
Before (OEM shocks)
After (Bilstein shocks)
Pavement @ 30 MPH
Pavement @ 40 MPH
Pavement @ 60 MPH
Uneven road @ 30 MPH
The lower-speed data indicate that the Bilsteins do a considerably better job at keeping the passenger compartment quiet. (If these numerical differences don't impress you, remember that dB is a logarithmic measurement and that a difference of 3 dB represents a doubling in sound pressure.) While it's mildly curious that the Bilsteins were measured as a little louder than the OEM shocks at highway speed, I think I can attribute this to my inability to control all factors (such as wind noise, which was clearly a contributor to the higher-speed readings); there's no reason for the Bilsteins to be louder.
The most impressive comparison to me is the difference on uneven road. This was only a mildly uneven surface, but the Bilsteins still succeeded in reducing the sound level by almost a full dB. I imagine that on even rougher road, the difference would be even more noticeable. Clearly, Bilstein's reputation for building a quieter shock is well-deserved.
This project was a bit of an eye-opener for me: while I suspected that my old shocks were on the way out, I really didn't expect to find such noticeable improvements in ride, handling and noise. Based on my findings, I can heartily recommend Bilstein shock absorbers, and installing them yourself, to my fellow truck enthusiasts.