Rear Diffuser & Spats

MK7.5 R

Tools needed:

Diffuser Install



1.Put the car on flat ground, in park, or first gear with the ebrake engaged. Jack up the rear of the car with a floor jack or bottle jack using the rear jack points. Place jack stands or cribbing under the control arm. Remove the rear tires. It is good practice to place the tires under the pinch seam of the car as a safety measure if a jack stand moves or fails. 

2. Remove the three T25 torx screws that hold the back of the wheel liners to the bumper. Two inside the wheel well, and one going up into the bumper from below. Repeat on the other side. 

3. Pull the liner forward. Looking into the bumper cavity you can see the two T25 screws that hold the plastic bracket to the edges of the valence. Remove both on each side. 

4. Take note of how the bumper lip and valence lip are sandwiched inside this clip. We will need to reinstall it in the same way. 

Pull the outer edge of the clip towards the center of the car. Once the outer edge releases, slide the second half of the clip forward. 

5. Open the diffuser box, remove the packaging. Identify the smaller and larger baseplates. With the machined pockets of the larger baseplate facing up, slide the fins onto the baseplate. 

6. Then place the smaller base plate on top with the countersunk holes facing up. Use the fin screw holes, and brass inserts to align the two parts. Install the black M4 bolts using a Phillips head screwdriver. 

You can use thread locker on these screws, however it is not necessary. They just need to be snug, do not over-tighten. Fasteners this small can be easily stripped. 

Once all 4 fin screws are attached, slide the large baseplate forward or back until all the 6mm holes between the two baseplates line up.

7. Locate the M6 bolts, and nylock nuts in the hardware bag. Grab your clamps, a 4mm Allen key, 10mm wrench and a drill with the 6mm or ¼” drill bit. 

The next steps are shown on a workbench for better lighting. You do not need to remove the valence from the car. 

8. Hold the diffuser up to the valence. Hook the fins over the OEM valence fins. Then rotate the front edge up under the car, and press the diffuser onto the valence one fin at a time. Work from one edge to the other. (This picture shows the valence upside down since it is on a bench). 

9. The front edge of the diffuser will sit flush with the bottom of the OEM Valence edge. The diffuser will hold itself in place. Make any micro adjustments left or right as needed before drilling in the next step. 

10. Wear safety glasses and drill the two center holes with a 6mm or ¼” bit using the baseplate as a guide. Install two bolts, and nylock nuts. Hold a wrench on top, and turn the bolt with the allen key. 

Now drill the remaining holes in the baseplate, and install the hardware. 

Spat Install

1. The spats are left / right side specific. The countersunk holes will be on the bottom. The narrow end of the spat should be closest to the wheel well. 

2. Have a clamp ready, or second set of hands to help hold it in place. Hold the small spat up to the edge of the valence/bumper. Line it up with the front & outside lip of the valence. The countersunk hole should be visible. Drill (¼” or 6mm drill bit) the countersunk hole, then install an M6x20mm bolt and nut. Tighten it until the spat is tight to the diffuser.  

3. Then drill the non-countersunk hole in the small spat. 

Starting with with a long M6 bolt, slide on the large spat (countersunk side down), nylon spacer, slide it into the small spat and valence, then the nut on the back. Snug this down, but do not fully tighten it yet. 

4 Rotate the large spat until the outside edge lines up on the valence. Drill (3/16” or 5mm drill bit) the outermost hole, then install a M5 bolt and nut. Repeat for the inner hole. 

5Repeat for the opposite side. Reinstall the valence clips onto each side. Some models may require trimming the clip on the lower edge to clear the nuts that hold the spat in place. You can use a file, or a dremel with sanding pad. 

6. Reinstall the clip screws. Line up the fender liners, and reinstall the three screws on each side. 

Reinstall the rear tires. Once the car is back on the ground, torque the lug nuts.