#### corneileous

##### Newly Enlightened
Hey guys, I’m not asking why the front of your vehicle should be 25 feet away from whatever it is you’re using to aim your headlights with or why you should aim your headlights two inches below whatever the measurement is from the ground to the center of your headlights but what if you can’t back up 25 feet away from the wall or garage door that it is that you’re using? Do you still measure down to inches and aim for that spot or can you compensate for that by measuring down an inch and a half or inch and three-quarter?

The reason why I’m asking is because due to the slight slope of my driveway, I could only back up about 19 or 20 feet away from my garage door before my driveway started to level out and instead of measuring down 2 inches to aim for, I just measured down an inch and 3/4. Was that the right thing to do to get roughly the same results at aiming 2 inches below at 25 feet away?

Thanks.

#### EJR

##### Newly Enlightened
Here is how the numbers work out at 25 feet:

1 inch down = -0.19°
2 inches down = -0.38°
3 inches down = -0.57°

And here is what they are re-calculated to 20 feet:

13/16 inch down = -0.19°
1 9/16 inch down = -0.38°
2 3/8 inch down = -0.57°

These numbers don't quite round up to the nearest quarter inch. And rounding up/down an 1/8 inch to make it easier would result in a +/-1 inch difference at 50 meters and +/-2 inch difference at 100 meters. So I'd recommend you place your tape marks to the exact measurement as shown above. Roundabout aiming is not a good practice.

What is the percentage of slope for your driveway?

And what vehicle make/model/year is this?

#### corneileous

##### Newly Enlightened
Here is how the numbers work out at 25 feet:

1 inch down = -0.19°
2 inches down = -0.38°
3 inches down = -0.57°

And here is what they are re-calculated to 20 feet:

13/16 inch down = -0.19°
1 9/16 inch down = -0.38°
2 3/8 inch down = -0.57°

These numbers don't quite round up to the nearest quarter inch. And rounding up/down an 1/8 inch to make it easier would result in a +/-1 inch difference at 50 meters and +/-2 inch difference at 100 meters. So I'd recommend you place your tape marks to the exact measurement as shown above. Roundabout aiming is not a good practice.

What is the percentage of slope for your driveway?

And what vehicle make/model/year is this?
So in other words I overcompensated according to your formula by measuring down too much to an inch and 3/4 instead of an inch and 9/16 which means my headlights are aimed a little lower than they need to be.

Maybe this weekend if I have time I’ll readjust to those measurements.

As far as the slope percentage of my driveway, I have no idea but it’s really not that steep. My driveway is about 40 feet from the garage door to the point at which it starts to level out by the street, and from that point when it starts to level out, there’s probably about the difference of 12 inches in grade to give you an idea.

Vehicle is a 2018 Ram 1500 with factory projector headlights.

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#### MB107

##### Newly Enlightened
Bottom line it the further you are away the better your resolution will be of your measurement. For example +/- 1/8" at 12.5' is the same at +/- 1/4" at 25'. Therefore if you can only measure to within 1/4" 12.5' might not cut it. On the other hand if you go to far away, you may not have a crisp enough cutoff line to measure accurately.