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BMW E30 Suspension Reinforcements
 
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Pelican Technical Article:

BMW E30 Suspension Reinforcements

Robert Bowen

Applicable Models:

BMW E30 3-Series (1984-93)
The CarTech BMW 3-Series Performance Guide

Whether for on-track duty or simply improved street performance, the E30 series cars have proven to respond to well-chosen upgrades. The CarTech BMW 3-Series Performance Guide offers current and future owners a wealth of important information, including a buyer's guide, year-by-year upgrades and changes, and more. This book is a valuable addition to every BMW owner's library, and Pelican is proud to present you with the excerpt below.

Suspension Reinforcements

In the same way that bushing deflection and movement hurts handling, so does flex and movement in the chassis. The control arm and strut attachment locations move slightly during cornering, which introduces an element of unpredictability at high speeds.

The most common addition to the front is a strut tower brace or stress bar between the strut towers. The towers pull apart during hard cornering and a strut tower bar ties them together for added stiffness. Another common bolt-on reinforcement is a rear tie bar, which connects the rear shock towers. These bars are very nice to have on road race cars. Street-based cars may not ever be driven hard enough to notice the difference.

A commonly added part that isn't really a reinforcement is a skid plate. The M20 oil pan sits quite low on a lowered car; one way to protect it is by bolting on a thick, steel skid plate. The rear subframe also tends to bend and move under hard cornering. Reinforcement plates around the differential mount and the rear control arm mounts help eliminate most of this deflection.

The rear upper shock mounts put a lot of stress into the chassis in this area and can cause cracking. BMW realized this after the fact and designed a stiffening plate for the Z3 that helps distribute the loads from the rear shock into the chassis. These stiffening plates (PN 51-71-8-413-359) go inside the trunk and help spread the load over the entire sheet metal shock turret.

If you need even more reinforcement, or if your shock towers are already cracked, BMW sells reinforcement panels (PN 41-14-8-169-027 and 41-14-8-169-028) that go on the outside, strengthening the entire tower. These plates have to be welded onto the towers, which is not incredibly difficult but does require some care to position them correctly and weld without overheating the metal around the repair (which causes it to crack again prematurely).

The better the subframe is located in the rear, the less the rear geometry changes in a corner and the better the car handles
Figure 1

The better the subframe is located in the rear, the less the rear geometry changes in a corner and the better the car handles. Use the hardest material you can stand. (Photo Courtesy Vorshlag Motorsports)

Stock rear upper shock mounts do not withstand the force of stiffer than-stock rear shocks
Figure 2

Stock rear upper shock mounts do not withstand the force of stiffer than-stock rear shocks. Most coil-over manufacturers ship their rear shocks with replacement spherical mounts. (Photo Courtesy Vorshlag Motorsports)

The rear upper shock mounts are a weak point of the E30 chassis
Figure 3

The rear upper shock mounts are a weak point of the E30 chassis. The rubber tends to tear and separate, causing noise and poor control of the rear damping. Replace them with urethane mounts such as these Ground Control pieces for the ultimate in strength. (Photo Courtesy Ground Control Suspension Systems)

The age of most E30s means that a lot of the suspension pickup points are becoming fatigued and cracks are common
Figure 4

The age of most E30s means that a lot of the suspension pickup points are becoming fatigued and cracks are common. A few strategic gussets can solve most cracking troubles and make the car handle better.

A strut tower bar like this one helps the suspension do its job instead of wasting any movement on flexing the chassis in this area
Figure 5

A strut tower bar like this one helps the suspension do its job instead of wasting any movement on flexing the chassis in this area. With stock springs and tires the effect is negligible, but it sure looks good. (Photo Courtesy Christian Bouchez)

A strut tower bar, such as this Vorshlag unit, should attach solidly to the strut towers to strengthen the chassis
Figure 6

A strut tower bar, such as this Vorshlag unit, should attach solidly to the strut towers to strengthen the chassis. Any movement here eliminates the effect of having the bar in the first place. (Photo Courtesy Vorshlag Motorsports)

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Page last updated: Wed 12/7/2016 02:24:49 AM