Pelican Technical Article: Replacing Shocks & Springs Wayne R. Dempsey
Time: 8
Tab: $1200
Talent:
Tools:
Spring compressor, floor jack, jack stands
Applicable Models:
986 Boxster (1997-04) 987 Boxster (2005-08)
Parts Required:
Shocks, springs and hardware
Hot Tip:
Purchase an electric or air impact wrench for this task
Performance Gain:
Smoother, crisper handling
Complementary Modification:
Install performance springs and lower your suspension
This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.
Check out some other sample projects from the book:
One of the most popular projects to perform on the Boxster is the replacement of the front and rear shocks. I usually recommend that you replace both the front and the rear at the same time, as they take roughly similar abuse over their lifetime, and the fronts or rears are not likely to be more or less worn than the other ones. As a rule, the shocks should always be replaced in pairs (left and right together). The replacement procedures for the front and rear shocks are very similar.
I recommend that you replace your shocks every 50,000 miles or so, or if they start to show signs of fading or wearing out. If you push down on a corner of the car, it should spring back with almost no oscillation up and down. If the car bounces up and down, then you probably need new shocks. Different driving patterns may also affect the life of shock absorbers. Cars that are raced or often driven on windy roads may need to have their shocks replaced more often than street cars. It is also important to remember to have the car realigned if you install performance springs into your car that lower it from its stock level. Changing the height of the suspension changes the values of the alignment / suspension settings.
With the car elevated in the air and the wheels removed, start with one strut, and remove the brake caliper (see Pelican Technical Article: Replacing Shocks & Springs). Unplug any brake sensors that may be connected to the caliper and disconnect them from the strut (see Figure 1). Use some rope or wire to tie the brake caliper aside so that it doesn't hang by its rubber hose. Now, disconnect the sway bar drop link from the wheel bearing carrier (see Figure 2). In the front trunk compartment, mark the location of the three nuts that hold the shock to the tower and then remove them (Figure 3). Finally, loosen but do not remove the bolt that attaches the wishbone to the chassis (see Figure 4). This will allow us to drop the strut downwards to its lowest point, so that we may pull it out from the car after we remove the shock insert and spring.
With the strut assembly and wheel bearing carrier loose, you should be able to push down on the wishbone and maneuver the shock down over the top of the fender. If your car has been lowered or has had some other suspension changes made from the stock configuration, you may need some extra wiggle room. In this case, use your spring compressors to compress the spring and remove it while the strut is still under the fender. Then you should be able to compress the shock further, and remove it from the bottom of the fender. When working close to the fender here, be careful that you don't scratch your paint: lay a moving blanket or something similarly soft out to protect the paint finish.
With your strut assembly off and on your workbench, install your spring compressor onto the spring and compress it until it no longer is tight in the strut assembly. While compressing the spring, be sure that you wear safety goggles: these springs are under a lot of pressure, and it is possible that the spring compressor may slip off suddenly. Place the two halves of the compressor on exactly opposite sides of the spring. I have found it very useful to use two ratcheting wrenches (I prefer the ones manufactured by GearWrench and available at PelicanParts.com) on each side of the compressor to assure that I achieve even and equal compression on both sides. Failure to maintain even compression when compressing the springs can make the compressor slip off.
With the spring compression removed from the strut assembly, and the springs loose on their perches remove the center nut that is attached to the top of the shock (see Figure 6). The reassembly process on the Boxster doesn't necessarily require an impact wrench, but it can sometimes make the job easier. So if you don't have one, now is a great time to buy one. I recommend an electric one: no air compressor is required (see Tools of the Trade in the front of this book).
With the upper strut mount removed, you should simply be able to lift the old spring off of the bottom spring perch. If you are reusing your old springs, then simply place them back onto the top of the lower spring perches. If you are replacing your springs with new ones, then move the spring to your workbench and slowly release the spring compressor on your old springs. Compress the new springs in a similar manner. You can use stiffer springs like Eibach Performance Springs, which serve to create a stiffer suspension and lower the car a little more than an inch in both the front and the rear.
Install the compressed spring assembly back onto the lower spring perch and reassemble the assembly as per Figure 8. Reinstall the dust boot / rubber bumper assembly over the shock to protect it from road debris and grime. Reinstall the upper spring plate and spring pad, taking care to verify that the plate is nestled correctly against the top of the spring. Inspect your upper strut mount and bearing carefully prior to assembly. The mount is manufactured out of rubber: both the rubber mount and the bearing will wear over time. I recommend replacing both of them if they look old, or if they haven't been replaced previously. Reinstall the upper strut mount on top of the spring plate, and tighten up the retaining nut. Always use new hardware when replacing your shocks: all of the nuts are self-locking and will loose some of that self-securing ability if they are reused.
Reinstall the shock assembly into the wheel carrier, and attach the lower sway bar drop link (which also functions as the pinch bolt for squeezing the shock assembly). Install the assembly back into the top of the shock tower. The upper strut mount may have to be rotated a couple of times in order for you to properly line up the studs integrated into the mount with the holes in the chassis tower. Attach the three nuts at the top of the tower, lining them up with the marks you made when you removed them. Reinstall the brake caliper (Pelican Technical Article: Replacing Shocks & Springs) and any other components you may have disconnected. Plug in the sensor connectors that you may have disconnected, and route the wires and hoses back through the tabs in the strut.
Figure 1
With the cable disconnected from its holder, make sure the wheel speed sensor and brake pad sensors are unplugged from their connector (green arrow). Then remove the bracket entirely by unbolting it (yellow arrow).
The shock (yellow arrow) is held onto the wheel carrier (blue arrow) by a long bolt that is integrated into the sway bar drop link (green arrow). Remove the bolt / sway bar link, and then the shock should be free to be pulled out of the wheel carrier.
An electric impact wrench is a very handy tool for both removing and installing new shocks. The tool allows you to tighten nuts without having the shock shaft rotate. The three nuts that hold the front shock to the tower are shown by the yellow arrows. The three nuts that secure the rear shock mount to the chassis are hidden from view: two are located near the rear of the engine compartment, and the third is accessible only through an access hole in the sheet metal in-between the trunk and the engine compartment (inset photo). Mark the position of these nuts prior to removal: you want them to be in the same spot when you put them back on.
The yellow arrows in the photo show the bolt that needs to be loosened in order to gain enough clearance to lower the shock and clear the edge of the fender. You don't need to remove the bolt: simply loosen it so that the arm can rotate a bit more than is possible through the deflection of the rubber bushing. Don't retighten this bolt until the car's tires are back on level ground and the suspension is fully loaded. In the lower right is shown a new bearing installed in a new front strut mount.
With the wheel carrier supported by your jack, lower it down so that you have enough clearance to rotate the assembly out from under the fender. Then, pull on the shock to remove it from the wheel carrier (green arrow). Watch out that you don't accidentally scratch your paint.
Use a hex socket to hold the shaft of the shock as you tighten the nut and clamp down the entire assembly. In order to get the springs compressed enough to be placed on the shock, you will need a spring compressor like the one shown in the upper left. When the assembly is clamped down with the locking nut, then carefully release tension on the spring compressors and remove them.
When replacing shocks, I recommend installing new parts. Shown here are a new front shock (A), a new strut bearing (B), a new lock-nut (C), and a new front strut mount (D). Your Bilstein shocks should come with a beveled washer on the shaft (green arrow).
This diagram shows the installation of a new front shock and how all the bits and pieces fit together. These new Bilstein shocks came with a tapered washer that needs to be fit to the shaft prior to assembly (see Figure 7). Shock Bellows Spring Bumper stop Cup washer Foam insulator Upper strut bearing Upper strut mount Cup Washer Nut
When removing or installing the shock, be sure to remove and replace the wire harness for the brake pad and wheel speed sensors. Don't forget the beveled washer when installing the new shocks (inset).
Replacement of the rear shocks is quite a bit more difficult than the front because you need to disconnect quite a bit more parts on the suspension. Replacement of the rear shocks require removal of the axle nut (hard) or disconnection of the CV joints from the transmission (easier). The green arrow shows the CV joint / axle disconnected from the transmission - with the axles disconnected, you can rotate the shocks out under the edge of the fender. The yellow arrow shows the track rod disconnected from the wheel carrier. The purple arrow shows the wishbone disconnected from the chassis mount. The orange arrow shows the control arm disconnected from the wish bone. The red arrow shows the rear chassis reinforcement bar disconnected. In this photo, the shock has been already removed from the wheel carrier (white arrow). See Project 41 for more information on the CV joints.
Comments: RATHER THAN TAKING THE STRUT OUT AS A UNIT... CAN I RAISE THE ASSEMBLY, COMPRESS THE SPRING TAKE OFF THE SHOCK NUT, DECOMPRESS AND TAKE OUT IN MULTIPLE PIECES, THAN REVERSES PROCEDURE.
May 9, 2012
Followup from the Pelican Staff: I'm pretty sure that if you do that, you will not have enough clearance to pull the shock out from under the fender. Perhaps if you used a spring compressor, but I don't think that will work well either (I think we tested that method when writing the book). - Wayne at Pelican Parts
pedro
Comments: the front shocks driver side of my 1997 boxster is leaking oil.is this a signal that i should replace my front shocks? when i push down on the front driver side it springs back up with no oscillation. traces of oil are evident on the shocks.i have purchased your book and am now ready for project 63 as soon as you say i have to replace the shocks.
September 13, 2011
Followup from the Pelican Staff: Believe it or not, Bilstein states that some leakage of fluid from the shocks is a normal occurrence. I personally never felt super-comfy with this analysis from them. But, they will not take shocks back under warranty if they are leaking. Hard to believe huh? Back to your question - if it were my car, I would replace the shocks, probably on all four corners. If one is leaking, the the others are probably not too far behind. - Wayne at Pelican Parts
Jeremy
Comments: I would also like to know an answer to JT's question above. I think he is talking about the bumpstops. Can they be replaced without removing the shock?
September 12, 2011
Followup from the Pelican Staff: Nope, they cannot be replaced without taking the shock off. They have a hole in the center and fit down the center of the shock. I suppose if you wanted to replace them without taking out the shock, you might be able to buy a new one, cut it in half, and then put it on the shock and fasten it with some type of tape or zip tie. But that approach is not ideal of course. I'm not sure how long they would last, or whether that would even work terribly well. - Wayne at Pelican Parts
JT
Comments: is it possible to change the foam insulator on 996 front suspension without taking of the shock? Regards John
June 14, 2011
Followup from the Pelican Staff: I suppose that you could cut out the old one and the put a slit in the new one and slide it on, then wrap some type of zip tie around the new one. But, this would not be ideal. - Wayne at Pelican Parts
Hal
Comments: Hi Wayne, quick question. In Figure 8 above you clearly do not list 'Support Ring' brass cover over the top of the 'Shock Bearing Plate'. My question, is that brass cover over the bearing really just overkill, is there likely damage to the bearing if it isn't there? The bearing is pretty rugged and the 'Foam Insulator' provide cushion from the spring end. I know it's funny question, but like always there is a reason behind a question :.
December 27, 2010
Followup from the Pelican Staff: Hmm, somehow the caption for this photo got cut off:
A- Shock
B- Bellows
C- Spring
D- Bumper Stop
E- Cup Washer
F- Foam Insulator
G- Upper Strut Bearing
H- Upper Strut Mount
I- Cup Washer
J- Nut
As for your specific question, there are no brass pieces on this assembly - you probably mean the two cup washers, which are yellow-plated steel. Both are very vital to the proper operation of the whole strut assembly. - Wayne at Pelican Parts
Check out some other sample projects from the book:
