Headlight Adjustment - Proper

Taz56 · February 5, 2020

I am curious on headlight adjustment if anyone knows.

I am curious on headlight adjustment.

I own a 2019 GMC Sierra AT4. I Googled how to determine headlight height. I found this:

Park against a wall on a flat surface. Mark with tape or chalk the horizontal and vertical points of the headlights on the wall.

Back up 25 feet and adjust (if needed) so at 25 feet away they point in the same spot.

However in my case I do not feel this is any longer relevant as I have put bigger tires on and done a front end level kit. So my stance against a wall is no longer “factory”.

Is there a "height" and “width” that I should aim for, Google is not being very helpful with that.

AD80 · February 5, 2020

Their should be a small dot or indentation on the front of your headlights , marking the center. Measure from that dot to the ground. Back up 25 away from the wall. Your light cut off point should be about 2" lower than your first measurement. So if your headlights are 47" from the ground, the top of the cut off line should be 45" on the wall when 25 feet away. I dont know if this is the official way to do it, but this is seems to be the way folks are doing it, and it should get you in the ballpark.

Edited February 5, 2020 by AD80

Taz56 · February 5, 2020

27 minutes ago, AD80 said:

Their should be a small dot or indentation on the front of your headlights , marking the center. Measure from that dot to the ground. Back up 25 away from the wall. Your light cut off point should be about 2" lower than your first measurement. So if your headlights are 47" from the ground, the top of the cut off line should be 45" on the wall when 25 feet away. I dont know if this is the official way to do it, but this is seems to be the way folks are doing it, and it should get you in the ballpark.

Sounds the same as what I posted. I assume the 2" you are referring to is to make up for the tires and leveling kit?

aseibel · February 5, 2020

No, the 2" inches means your lights should be aimed slightly downhill. So 2" over 25' is only about 1/3 of a degree below horizontal. That should keep your low beams from blinding oncoming drivers.

your "instructions" are for people who don't own a tape measure apparently. You don't even need a wall. If you park in a flat area, measure the centerline of the bulb, then stand 25' away and measure the cutoff line again, it should be 2" less than the light bulb center.

Edited February 5, 2020 by aseibel

Taz56 · February 5, 2020

4 minutes ago, aseibel said:

No, the 2" inches means your lights should be aimed slightly downhill. So 2" over 25' is only about 1/3 of a degree below horizontal. That should keep your low beams from blinding oncoming drivers.

I get that, but what I was asking is, do I go "more than 2"" because I lifted my trucks front end and I put on bigger tires?

When I bought the truck lets say (for example only) that I was at 43" for the headlight, when I installed bigger tires and leveled the front end I am now at 49" Going down 2" brings me to 47" which is still higher than I was stock and I am still blinding people.

The point of this post was to ask what it should be at as I did not think to measure before I lifted the front end and put on bigger tires.

Edited February 5, 2020 by Taz56

aseibel · February 5, 2020

Just now, Taz56 said:

I get that, but what I was asking is, do I go "more than 2"" because I lifted my trucks front end and I put on bigger tires?

When I bought the truck lets say (for example only) that I was at 43" for the headlight, when I installed bigger tires and leveled the front end I am now at 52" Going down 2" brings me to 50" which is still higher than I was stock and I am still blinding people.

The point of this post was to ask what it should be at as I did not think to measure before I lifted the front end and put on bigger tires.

It doesn't matter what the old height was. As long as your lights are pointed downhill NOW, they shouldn't blind people unless you are tailgating them or parked directly behind at a stoplight/mcdonalds drive through.

forget about the "before" and just measure at the new light C/L and at 25' away. that's all that matters.

Taz56 · February 5, 2020

Just now, aseibel said:

It doesn't matter what the old height was. As long as your lights are pointed downhill NOW, they shouldn't blind people unless you are tailgating them or parked directly behind at a stoplight/mcdonalds drive through.

forget about the "before" and just measure at the new light C/L and at 25' away. that's all that matters.

OK. Will do.

mafd2 · February 9, 2020

I can tell where the cut off point on the road should be on dim. I've set many sets and projector lights as well on lowered and leveled trucks. I use a level slab and a brick wall to level the left and right headlights the same using the bricks or mortar joints. Aim is perfect and I never get flashed.

redwngr · February 9, 2020

Whatever measure/adjustment method is selected, the verification is still how other vehicles respond.

Frequently getting flashed on level roads means they are to high.

A head-on because a blinded driver that drifts into your lane can make for a bad evening.

JansterZ71 · December 4, 2020

On 2/5/2020 at 9:26 AM, Taz56 said:

I am curious on headlight adjustment if anyone knows.

I am curious on headlight adjustment.

I own a 2019 GMC Sierra AT4. I Googled how to determine headlight height. I found this:

Park against a wall on a flat surface. Mark with tape or chalk the horizontal and vertical points of the headlights on the wall.

Back up 25 feet and adjust (if needed) so at 25 feet away they point in the same spot.

However in my case I do not feel this is any longer relevant as I have put bigger tires on and done a front end level kit. So my stance against a wall is no longer “factory”.

Is there a "height" and “width” that I should aim for, Google is not being very helpful with that.