Behold, the Moosehead Engineering spherical Upper Control Arm Bushings (UCABs).

After having destroyed two sets of urethane UCABs, at great cost, I went on a mission to find something better, and these are the result.

Bushing breakdown info below. The short version: These are the ultimate replacement bushings for the upper control arms on your E39 540i or M5. They will be the last bushing you ever need to buy. FREE shipping in the US*!

To order, please specify what configuration you’d like. These are available in the following configurations:

Just UCABs: Includes one pair of assembled and lubed UCABs.

UCAB Kits:

Gold kit: Includes pair of assembled and lubed UCABs, one set of replacement races, and one lock ring adjustment tool

Platinum Kits: The picture above is representative of the E39 control arm, however the E53 X5 does not have an arm with a ball joint. While I can source arms and press the bushings into them, the arm itself is not a wear item. Contact me if you need set of bushings pressed into the tension arms for your E53 X5.

*Shipping cost to the CONUS is included with all UCAB orders. Please contact us for international orders.

The Moosehead Engineering UCAB is a type of spherical joint. It is not like a bushing since it incorporates a ball pivot. Here you can see the parts that make up the UCAB. One of the best parts of all- these are made in the USA.

By ordering from this site, you agree to out shipping policies here.

Long drawn out dissertation on bushings

There are basically 3 different types of upper control arm bushings:

There is the stock type of elastomer bushing that uses a sleeve cast into rubber. These are available in regular and heavy duty (the heavy duty variant was developed as an alternative to machining E32 bushings to fit the E24/28.) They are designed to give so that there is less noise, vibration, and harshness known as NVH. Unfortunately, this give allows the wheel to move back under braking and to the side under cornering loads. The sleeve dose not pivot in the rubber, it twists the rubber as the wheel moves up and down. Eventually, the rubber degrades and tears from this twisting and back and forth motion. The result is that there can be uncontrolled oscillation in the steering at certain speeds (shimmy.) This wear and shimmy is exacerbated by sticky modern tires, larger wheels, and wider tires than the factory sent these cars out with. This poses a problem since many people like to track their car with 17″ wide wheels sporting 225s or even 245s.

The next is a solid urethane bushing. This was the standard performance upgrade for these cars for many years. There is an NVH penalty to be paid paid because they do not flex as much. Without the squishy rubber and voids cast into the stock bushings to soak up shocks, you hear and feel sharp bumps more. Performance drivers feel this is a worthwhile tradeoff. Unfortunately, the urethane is a bit soft and the hole where the sleeve lives will get wallowed out eventually and the bushing will fail. This issue is more pronounced on the passenger side of the car because of exhaust heat. These urethane bushings can also squeak. In addition, the shells for these urethane bushings are usually very thin so the bushing cannot be pressed back out of a worn control arm. Worst of all is knowing that you’ve shelled out your hard earned bucks for something that won’t last.

The last design is a racing upgrade. It is a spherical bearing with a metal bearing race. These have zero play when new and allow for very sharp steering and suspension action. There is an even higher NVH penalty to pay due to the complete lack of damping from the all metal joint. In addition, once there is wear in the joint, it is completely useless and must be replaced. They are usually not sealed to protect them from the elements so road grit will wear between the ball and the race. The bearing itself can usually be pressed out of the housing once worn out, but it is usually pretty expensive (in excess of $40 per bearing.) Again, these are normally only used on race cars. These can be pressed out of the arm and reused, though.

The Moosehead Engineering UCAB is sort of a hybrid between the spherical bearing and a polymer bushing. The ball is made of nickel plated steel and the races are made of Nylatron GS, which is a molybdenum impregnated nylon formulated for bearing races. They can be rebuilt for ~$12 each. They can be greased. Once there is wear in the race, the design of the bushing allows the races to be tightened to remove the play. I have had mine in my daily driver wagon for almost a year now and there is no sign of wear. When the ball joint at the wheel end of the arm is used up, the Moosehead UCAB can be easily pressed out of the control arm and pressed back into a replacement arm, which means you don’t have to wait until it is time to replace the control arm to upgrade to these joints. Since this a spherical joint, it has all the advantages of the racing type, but because the races are Nylatron and have a little bit of give, the increase in harshness is not as pronounced, I notice it most when I hit a sharp bump like a manhole cover or a deep pothole. They give razor sharp steering response, especially right on the initial turn in and in transitional esses. They eliminate braking shimmy and greatly reduced tramlining from wide tires. They are suited to performance drivers and are even suitable on the track, so they are great for drivers that autocross and go to HPD events. In addition, if you have adjustable coilovers, these will allow you to adjust ride height up and down without having to worry about the effect on the bushing.

The installation of these bushings is as easy as the installation of any upper control arm bushing, but they must be pressed in. Check our our DIY installation instructions here.