This is a common problem on many of the older vehicles that have operated for too long with severely worn or leaking shock absorbers. The first indication of a problem is when the installer attempts to install a new stress bar or shock tower mounts and the 3 hole bolt pattern of the new mount or stress bar appears to be incorrect. The bolt pattern of the new product appears to be smaller than required. Since these products are typically punched pressed on a jig or drilled in a close tolerance environment, the problem may not be in the replacement component. It may be time to take a closer look at the actual shock towers of the vehicle.

Here is what has most likely occurred. Due to the poor dampening ability of the worn shock, the internal piston has bottomed out on the compression stroke, sending a severe impact to the inside of the shock tower, causing the shock tower to distort or bulge. This widens the bolt pattern of the 3 mounting studs. In some cases repeated impact will have deformed the tower by as much as 3/8 of an inch.

To identify and correct the problem is simple. Prior to removing the original mounts check out the alignment of the studs at eye level. It is important that the 3 studs exit the tower perpendicular to the top of the tower mount, and that the tower mount is flat at the mount inner contact surface. To get a clear view you may want to remove the three 8mm nuts. Make sure you remove these only with the vehicle firmly weighted on the ground. Do not do this with the vehicle on jack stands since the struts will drop from the shock towers.

If the studs are tilted outward, even the slightest amount, fitment of a new mount or a stress bar will be a problem. Now is the perfect time to correct this situation. To do this I recommend using a copper or brass hammer. Screw the nut onto the stud so the stud is even with the top of the nut. Tap the nut on the outer edge until the stud is in perfect straight-up alignment.

In cases when the shock tower has severe bulging. You may need to rely on a body shop to pound the tower down to a flat mount surface. To do this properly a machined round mandrel should be inserted into the top center hole of the tower, and then receive several blows of a 5 lb hammer. If you smack your finger, more often than not, when nailing a picture hanger, I don't recommend this portion of this project.

Now, to help avoid this problem in the future let's check out the shock absorbers, which are most likely, the cause of this problem. The original shocks or O.E. replacements have an average life of approximately 75,000 miles. This does not mean all shocks fail at this point. This is reference point for you to pay close attention to the ride quality. If you have concerns with the ride quality, and your shocks have in excess of the 75,000 average, we recommend replacing the shocks at this time. Shock absorbers deterioration begins the moment the vehicles leave the assembly line. Over load or severe bottoming out will damage the fragile shock valve components much sooner. Remember on an impact you are pounding the shock absorber valve assembly with a 4,000 lb car. The results can be damaged seals, valves, or a bent shock shaft. As the shocks and springs deteriorate over time the bottoming out episodes will occur more frequently.

How to check your shock absorbers:

Visual inspection: (1) Check the upper mount studs for damage, any deformation and the vehicles has most likely bottomed out. (2) Lift the vehicle and check for oil leaks around the seals where the piston enters the shock. A slight damp spot at the top is only the lubricant to clean the piston. This is not a problem. However, actual liquid leaking from the shock will require replacement. (3) Damage to the outer housing from road impact, or if you see lower bushing damage, will require replacing the unit.

Testing ride quality: With the car setting on the ground on a level surface. Use the weight of your body to attempt bouncing the vehicle. Once you have a momentum going and you then release, the vehicle should stop the bouncing motion within one stroke. While on a road test pay close attention to how the vehicle handles dips in the road surface. If the vehicle dives deep into dips the vehicle should rebound once and return to the neutral position. If the vehicle oscillates before retuning to the neutral position, or if the vehicle has a spongy ride, and does not feel like it did when it was new it may be time for replacement shocks.

Selecting new shocks:

For a comfort ride (original quality) we recommend selecting Bilstein O.E. replacements shocks. Bilstein is an original equipment supplier to the BMW factory and was closely involved with the development of the suspension of your BMW. Although there is several other off brands, none have invested the hundreds of hours required to perfect the ride quality of your BMW.

For a Street performance ride (more aggressive) there is only one real choice, the Bilstein performance shock. Bilstein has been the leading O.E. performance supplier for BMW for more than 20 year. Bilstein is also the supplier for most of the well known BMW tuners, simply because of their attention to manufacturing detail and performance ride quality. Be aware however that the Bilstein performance line will ride approximately 20% firmer than the original replacement shock.

Additional hints while Installing shock: (1) Always have your car aligned after shock replacement. (2) Always inspect ball joints, tie rods, and control arm bushings for wear and damage. Remember a proper alignment is impossible if your vehicle has play in the suspension or steering system. (3) To return the vehicle to perfect factory alignment specification, install a set of front and rear adjustable shock tower mount. (link to the K-Mac mount)

K-Mac shock tower mounts:

Why install a set of K-Mac shock tower mounts? The BMW factory assumes that all BMW's will remain as perfect as the day they rolled off the assembly line. For this reason the vehicle was designed with little or no adjustment for caster or camber alignment. Meaning that as the body settles, or components fatigue, there is little or no provision for proper alignment adjustment. The K-Mac system will allow up to 2.5 degrees of adjustment to help correct the alignment that may be the result of a miss-calculated encounter with a curb. Installing a set of K-Mac camber/caster adjusters will save you hundred of dollars in premature tire wear.