Offset vs Centered Front Control Arm Bushings and Control Arm Swap Guide for BMW 3 Series
Chances are if you're reading this it's because you're looking to replace or upgrade your worn out front control arm bushings on your 3 Series BMW. This article will help clarify the differences in the Offset and Centered front control arm bushings and help you select the correct bushings for your vehicle.
Before we begin we first need to talk about the 3 series front control arms. All E30s, E36s, and E46s use the same style "L" shaped front control arms. This is both good and bad. Good because that means that setups are nearly identical throughout the different models making some parts interchangeable. Bad because subtle changes to suspension geometry and bushings throughout the production range of certain models can make things confusing and can sometimes lead to improper fitment or misaligned front suspension.
First, we will start by differentiating the different control arms by model and discussing any changes they may have had during production runs.
Note: This article does not apply to any IX variant of the BMW 3 series.
E30s are the simplest of the three chassis. All RWD E30 models used the same front control arm. This includes the E30 M3. These control arms have a round male end that is inserted into the front control arm bushings. These are the same diameter as the E36 which makes it possible to install E36 control arms on E30s.
E36s are where things start to get confusing and are also where the offset front control arm bushing originated. In general all RWD non-M model E36s use the same front control arms. It wasn't until 1995 with the release of the M3 model that BMW changed the control arm design. This was because the E36 M3 used a different spindle than the other non-M models. This being the case BMW decided to change the caster on the M3s. They did this by changing both the strut top mount and control arm bushing designs. Both the strut top mounts and control arm bushings were revised and became offset. This is where most of the confusion on choosing bushings comes from. As stated above both the non-M and M model control arms use the same diameter round male end as the E30s. This means installing offset front control arm bushings on other vehicles is possible.
The E46 has three different variants. Two for the non-M models and one for the M model. Very early non-M E46s actually came with steel front lower control arms. These are extremely rare as they were ended in 07 of 1999 almost immediately after production started. They were replaced on all future models by an aluminum control arm. This arm in physical size is bulkier but is, in fact, lighter than the previous steel arms making it a better option for most enthusiasts. The M3 model also got aluminum arms. Like the E36 M3, the E46 M3 also uses a different front spindle. However, unlike its predecessor the E46 M3 front control arms will not work with non-m or any previous models. The only way to install E46 M3 arms on another chassis is to run E46 M3 spindles as the ball joint taper is different. E46s use a hexagonal-shaped male end and a hexagonal centered front control arm bushing. This means in order to use E46 control arms on older chassis an adapter bushing is needed.
E46 Steel Control Arms
Currently, these are no longer available through BMW.
E46 Aluminum Control Arms
E46 M3 Control Arms
Which Bushings Should I Choose?
Now that we understand the differences in control arms and which models used centered and offset bushings we can now decide which bushings to use. Below is a chart showing which bushings will work with which stock configurations. This means the original control arm and original control arm bushing for that model. We will discuss swaps and bushing choices down below. Selecting these bushings for your vehicle will keep your caster setting the same as the factory setting.
Increased Front Caster
For E30s and Non-M E36s if you are looking to improve driving feel increasing caster is a great way to make a noticeable change in how your car drives. Increasing caster is easy. By using the offset style bushings used on the E36 M3 you can easily increase your front caster. Keep in mind if you have an E36 M3 or E46 you will need to modify caster by either using an adjustable front lower control arm or by doing it via the strut mount. For non-M vehicles, all that is required to increase caster is to install offset front control arm bushings into your factory control arm brackets. This is even easier as E30, E36, and Z3 control arm brackets are all the same inner diameter.
Control Arm Swaps
As we talked about earlier. The great part about E30s, E36s, and E46s is that a lot of parts will actually interchange or can be adapted to fit with minimal effort. A common practice for E30 and E36 owners is to swap wider control arms on to their vehicle for more track width. E30s can use both E36 and E46 control arms. While E36s can use E46 only. If you're planning on swapping control arms you will have few options when it comes to swaps. Below you will find a chart with all possible options when swapping control arms on your E30 or E36
|E30||E46||Hexagonal||E46 Adapter Centered|
|E30||E46||Hexagonal||E46 Adapter Offset|
|E36||E46||Hexagonal||E46 Adapter Centered|
|E36||E46||Hexagonal||E46 Adapter Offset|
Adjustable Front Control Arm Bushings
These bushings are the ultimate upgrade for someone who wants to precisely align their vehicle. These offer the ability to precisely adjust caster where a fixed bushing keeps caster at a fixed setting. These are most suited for those with track-oriented vehicles. But can also be used on streetcars to correct minute differences in caster if so desired. These are offered for both E30s and E36s using both standard and swap control arms.
Lastly, for those wanting to run E46 arms you will need to measure the diameter of the hexagonal male end. These can vary in size depending on which brand and model control arm you choose. Most common are either a 21-22mm hex on standard grade arms or 24-25mm hex on HD arms. Once you have measured these you can safely order the correct bushing to accommodate your vehicle.