2008 Subaru WRX STi
HID Headlight Adjustment

The factory HID (low) beams come adjusted too low for my tastes. Their very sharp cut off at the top means that the beam pattern ends abruptly at the top. I suspect it may be something to do with DOT regs for HID lamps. Since they can be adjusted lower through the dial in the cabin, moving the highest setting up makes the beam pattern much more useful. In situations where you're carrying a load or extra passengers that compress the rear suspension, the HID low beams may end up aimed too high. In that case I can dial them down from the control in the cabin.

Controls in the Cabin:
The HID level adjustment wheel is to the left of the steering column; between the dash light brightness wheel and the traction control en/disable button.

Access to the height adjustment screws:
For this project we'll be working with Subaru's Phillips-headed plastic rivets. They are removed by holding the outer collar in place and turning the inner pin a quarter turn counter clockwise. To put them back in place, the inner pin is held up while the outer shank is inserted through the items to be held. Once the shank is seated fully, press the head of the inner pin until it clicks; locking the rivet in place.


Remove the upper retaining rivet to the windshield washer fluid filler. You can access the HID adjustment screw without removing this rivet but your access is limited and the limited range of motion causes the adjustment to take longer.

Windshield Washer Fluid Filler

Remove the air intake duct by removing the 2 Phillips-headed plastic rivets and carefully lifting out the intake duct.

Air Intake duct

From here both lamps are the same. Toward the outboard side of each HID is a white plastic slotted screw that operates the worm gear underneath. Trying to use a screwdriver can easily strip the slot. Instead an 8mm socket or box-end wrench makes short work of it without risking damage to the plastic. If you have a ratcheting box-end wrench then you're in high gear.

Left HID Assembly (Adjustment Screw Noted @ 9 o'clock)


Right HID Assembly (Adjustment Screw Noted @ 3 o'clock)


All clock references are as a driver, sitting in the car, looking forward.

Counter Clockwise raises the beam. Clockwise lowers it. Since it's a worm gear there may be a complete turn or two before any slack is taken up and before you see movement.

Target Height:
All measurements are with the cabin adjustment wheel set to zero. This is the setting where the beam pattern is cast the highest. You can then use the cabin's electronic adjustments to lower the beam when you are carrying a heavy load in the back since that causes the beam to shoot higher than normal loads.

1. Find a level place to park with a blank wall at 25 feet from the front of the car.
2. Place a mark (tape or something removable) 2 inches lower than the measured height of your HID lens (the outer lens in the headlight modules). Different tires, wheels, suspensions, etc. may raise or lower the front of the car, so be sure to get an accurate measure of your HID lense height. On my stock 08 STi with standard wheels and tires, the height is 27 inches.
3. The old-school method was to get get the middle of the beam pattern to be about 2 inches below the height of the middle of the lens on the car. We're all about the new tech, baby! The 08 STi HID beams have a very sharp cut off at the top of the beam pattern. When adjusting the beam height, set the top cut off line of the beam pattern on the mark placed on the wall. In this case, we're setting our mark at 25 (x-2) inches.

Beam Cast - Top of Tape is 25" Up
(The sharp cut-off is for US models to avoid blinding oncoming traffic.)

Cut-Off/HID/Color Discussion:
There are 6 settings available on the cabin controls (0-5 with 0 being the highest setting). I made this baseline adjustment with the control set at 2. The blue tape on the wall is at the typical 25" height from the parking lot pavement and the car is 25' away from the wall. With the base adjustment made at 2 I can crank the height up or down as needed for different driving conditions. Kept at 2 on the way home, no traffic flashed me for having the HIDs adjusted too high. The OEM setting was closer to the drain (on the wall to the right) than it was to the blue tape. As you can see the cut off is for US (right hand) driving to avoid blinding oncoming traffic. If you've ever approached someone with their HIDs adjusted wrong, you know that they can dazzle you and cause momentary night blindness.

The above photo is also a good example of a good HID's color temperature. I'd guess they are around 4500°K. They cast a usable, white light instead of a bluish light like the 6000°K and higher temps do. Bluish tint can mask road debris like gravel and sand and doesn't "reach" as far down the road (when comparing similar lamp designs) because of how the human eye processes blues.

Color shifting headlights and driving lights serves little useful purpose beyond appearances. Yellowish fog lamps aren't meant to reach a long way down the road; they are aimed low and tinted to reduce reflection from the fog. The assumption is that the driver will slow down in the fog so that a lamp aimed very low still gives time for him/her to react to changing road conditions. With driving lights, you want to see as far down the road as possible so that you can see debris, animals, curves, and other potential hazards in time to avoid them. Masking your usable lumens with bluish faux HID bulbs, HIDs with color temps that are too high, or masks applied to the headlight lens (paint or tinted film) all work against that goal. They block or shift the usable light and keep it from getting down the road where you need it the most.

Remember, we're more interested in "Seeing" than "Being seen".


Putting it all Back Together:
Remember that the rivets go through the lined up holes, you then push the center pin down to lock it.

When reinstalling the intake duct, take special care that the duct properly fits into the square opening in the air intake/air filter box (behind the passenger side headlight assembly).

Air Intake duct

Air Intake/Filter Box



(C) 1995 - Present, Mark Johnson. All rights reserved.