Congrats on your new MPP.R compression rod bearings! Pay close attention to the instructions so that you don’t install the bearings shells backward!
Theory & Setup:
The compression rod bearing allows for a 4mm adjustability in the caster of the front suspension. As caster is not something that is normally adjusted (there is no need to obsess over making the caster the same side-to-side, it is likely that the alignment machine’s accuracy and repeatability is quite poor), it wasn’t critically important to make this bearing a “quick” adjustment during alignments. Caster is the least sensitive of the three alignment adjustments, so focus your time on getting the camber where you want and the toe perfect.
Therefore, it is recommended to set the bearings to the length adjustment you would like and perhaps make one adjustment on the rack if needed if the caster or measured wheelbase varies significantly from side to side. Due to the nature of the part and the tight installation space, It is required to pull the compression rod out to make adjustments to the position of the caster bearing.
We opted to make the minimum setting +2mm, as the balljoint cannot give us more than 4mm of adjustment. This allows for a total of 6mm longer length than OEM, which is worth Adding more caster will also increase camber. It will move the wheel further forward in the wheel well, so clearance will need to be checked at the fender and bumper. We suggest using +2mm as a starting point and will do some testing at both extremes before providing any advice on how far is ideal. At this time we do not have any testing data on the +6mm position to report, although many customers have run that position successfully.
If the bearing shells are installed backwards, you will be reducing the length of the arm and have less caster than OEM. So make sure you get it right!
Time Required: 1.5 hours
Tools Required: Common metric wrench and ratchet set, T45 torx bit, 10 Ton press, common press tools (2.75″ tube), metal ruler, jack
Difficulty Level: 4/10
Step 1 – Jack Car
- Jack up the front of the car as high as you can, or ideally use a hoist.
- Secure the car on jack stands, or with a locking jack.
Step 2 – Remove OE Undertray
- Remove the OEM undertray. Leave the center bolt for last to make removal easier.
Step 3 – Remove compression rods
- The compression rod can be simply removed by removing the nut on the knuckle (22mm for the nut, T45 bit to hold the balljoint from rotating) and the compression rod bolt and nut (21mm) at the subframe.
- Note the nut on the top is not welded to the chassis, so make sure you don’t lose it!
Step 4 – Press out the original bushing
- Press out the OEM bushing using a hydraulic press
- Take care not to damage the compression rod
Step 5 – Align bearing housing and press into arm
- Important – the bearing housing must be pressed in so that the thick end of the bearing shell is facing the balljoint. The 6mm line must be facing directly towards the balljoint
- Press the bearing housing so that the engraved numbers are facing down (when installed on the car), so that they are visible if working on an alignment rack
- Press the bearing housing in until it is flush on both sides. Do NOT press on the bearing itself, you will destroy it. Ensure the press tool used does not damage the housing.
Step 6 – Set compression rod bearing to the desired length
- The compression rod housing is marked indicating the length offset relative to stock. The markings indicate the shortest length (2mm) as well as 3, 4, 5 and the longest length of 6mm.
- Using the factory bolt and nut, tighten the bolt and nut to the bearing, and turn with a wrench to set the bearing to the desired length.
Step 7 – Re-install and align
- Re-install the arm
- Torque the outboard nut (at the knuckle) to 180Nm (130lb-ft)
- Torque the inboard bolt (at the subframe) to 115Nm (85 lb-ft)
- Re-install the aero-shield / skid plate, install and torque the wheels and align.
- An alignment is required as the length of the compression rod changing will cause the toe to change. Extending the compression rod will cause the front suspension to toe in. Aligning with toe plates is totally acceptable. See our post and video regarding how to check and adjust your alignment with toe plates here
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