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BMW E39 Radius Arm Replacement
 
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Pelican Technical Article:

BMW E39 Radius Arm Replacement

Kerry Jonsson

Time:

4 hours4 hrs

Tab:

$200

Talent:

***

Tools:

21mm wrench (2) or 21mm socket with ratchet or wrench, 22mm wrench

Applicable Models:

BMW 525i Sedan/Wagon (2001-03)
BMW 528i Sedan/Wagon (1997-00)
BMW 530i Sedan (2001-03)
BMW 540i Sedan/Wagon (1997-03)

Parts Required:

Radius arm (aka Strut arm), radius arm bushing, fasteners

Hot Tip:

Loosen mounting nuts as much as possible before removing ball joints.

Performance Gain:

Tighter feel in corners, eliminate vibration under braking and increase tire life

Complementary Modification:

Change radius arm bushing or whole arm.

BMW's reputation is built on performance, power, handling and reliability. BMW uses aluminum arms in most of their suspension systems and they offer strength and light weight. After many miles of harsh roads and spirited driving ball joints and bushing start to wear. Over time this can lead to vibrations, poor road feel and uneven tire wear. Rebuilding your front suspension can restore the handling, elimination vibrations and extend tire life. The radius arm controls the fore and aft movement of the whole spindle. It improves stability under hard braking. When the bushing gets soft it can lead to a vibration under braking that feels like warped rotors. It does have an outer ball joint built into it so that gets replaced with the whole arm. The body side of the arm has a bushing that can be replaced separately but you need to have special tools to do it. Buying a special tool does increase the cost of the job but we will show you how to do it if you make the investment.

These fasteners are going to be tight and there is not a lot of room to swing the wrench. You are going to have to be patient and use some force to remove fasteners and components to rebuild your front end. Corrosion may hold a component in even after you have loosened a fastener. Keep in mind the joint may pop out when you use a removal tool so keep your hands clear and wear protective gloves.

Lift and support front axle of the vehicle. See our tech article on jacking and supporting your vehicle. You have to remove the front tires to perform this job.

The procedure to replace the radius arm is the same for both the left and right side. In these pictures we will be alternating between the left and right side. We will note it in the caption just keep in mind the step applies to both sides. It is recommended you replace both sides at the same time to keep your handling neutral.

Radius Arm Removal:
This photo illustrates the front left side wheel well.
Figure 1

This photo illustrates the front left side wheel well. We are looking at the radius arm (green arrow) that we are going to remove. This arm attaches the spindle to the front sub-frame

This photo illustrates the left side suspension looking up at the radius arm mounted to the sub-frame.
Figure 2

This photo illustrates the left side suspension looking up at the radius arm mounted to the sub-frame. You can use a 21mm wrench or a socket to hold the mounting bolt (yellow arrow) while using a 21mm wrench to loosen the 21mm mounting nut.

Use a vise grip or pliers to pull out the mounting bolt (green arrow) in the direction of the blue arrow.
Figure 3

Use a vise grip or pliers to pull out the mounting bolt (green arrow) in the direction of the blue arrow. You donÂ't have to remove the sway bar bushing (yellow arrow) but it will make getting to the mounting bolt easier. See our tech article on sway bar links and bushing removal. Note the position of the center link (red arrow) you may have to move the steering wheel to get the center link out of the way so you can pull the bolts straight out in the direction of the blue arrow.

Working at the right side radius arm sub-frame mount remove the mounting bolt (green arrow) by pulling it in the direction of the blue arrow.
Figure 4

Working at the right side radius arm sub-frame mount remove the mounting bolt (green arrow) by pulling it in the direction of the blue arrow. You do not have to remove the sway bar bushing (yellow arrow) but it does make it easier to grab the bolt. See our tech article on sway bar link and bushing removal. You will probably have to turn the steering wheel to position the center-link (red arrow) so it does not block the bolt from coming out.

This photo illustrates the spindle side of the radius arm.
Figure 5

This photo illustrates the spindle side of the radius arm. Remove the 22mm nut that secures the radius arm ball joint shaft to the spindle. I have removed the spindle to show you a clear picture of what you have to do. On the vehicle there will be the sway bar, and lower control arm limiting the movement of the wrench. You will not be able to back the nut out all the way because it will eventually hit the strut but take it our as far as you can.

With the nut partially removed you can use a separation fork here (green arrow) to help move the radius arm in the direction of the blue arrow.
Figure 6

With the nut partially removed you can use a separation fork here (green arrow) to help move the radius arm in the direction of the blue arrow. You can also use a chisel to hammer down on the radius arm ball joint shaft (yellow arrow) to force it out also. There is ball joint removal tools that you can use this is purpose also.

Avoid removing the ball joint shaft until you have the mounting nut removed as far as you can.
Figure 7

Avoid removing the ball joint shaft until you have the mounting nut removed as far as you can. If the shaft breaks loose you will only spin the ball joint shaft around in circles. In that case one option you have is to remove the strut and secure the radius arm shaft with a 6mm Allen head and wrenching off the nut. Installation is the reverse of the removal steps. Install the new radius arm in the spindle and force the ball joint shaft into place to hold it still while you tighten the nut. Most nuts are lock nuts and will require some force to tighten. This is so they donÂ't back of from vibration over time. Position the strut mount bushing, install the mounting bolt and tighten it down.

Radius Arm Bushing:

Remove the radius arm bushing mount as outlined in steps 2, 3 & 4.
Here is the universal bushing tool that Pelican Parts sells.
Figure 8

Here is the universal bushing tool that Pelican Parts sells. Use a bushing puller tool to force the bushing out of the arm. Spray some penetrating oil around the bushing to allow the bushing to slide out easier. It is a press fit so it will be very tight. You will have to use some force to get it off. They are a few different manufactures of this type of special tool. Follow the tool manufactures instructions to safely remove the bushing. Installation is the reverse of the removal steps. The bushing is to be installed in a specific position. There is an arrow on the bushing that you need to line up with an arrow on the arm. Follow the instructions of your special tool manufacturer to install the bushing and mount it in the sub-frame. Tighten down the mounting bolt and youÂ're done.

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Page last updated: Fri 12/9/2016 02:06:06 AM