From: "Alex Little" alittle@VNET.IBM.COM Subject: Aiming H4s - warning -- long note. Date: Thu, 23 Mar 1995 19:09:14 -0500 Miata Mailing List: March 95, Message #1254
>Well the Hella H4's in my Miata are definitely misaimed, as the bright >boundary region occasionally illuminates the occupants of other cars. In >fact the region illuminated is close to the pre-Hella high beam. It's been my experience that the horizontal cutoff line of a properly- aimed H4 low beam will hit just below the level of the trunk lid of the average Buick doing about 10 mph under the posted speed. It should provide just enough light to urge them to go faster. Seriously, it sounds as if you didn't reaim your lights when you converted from stock sealed beams to these new-fangled jobbies. Luckily for you, H4s can be aimed visually because of their precise optics. If you have the lights with a horizontal cutoff that rises to the right, here's how: (this will also work for Z-beams). (I'm doing this from memory, so pardon the rambling.) Wait until it's dark. Find a willing assistant; a second person helps tremendously. Also grab a 25 foot tape measure, a screwdriver that fits the headlight aiming screws, a roll of masking tape, and a felt marker. Fill your gas tank prior to aiming. Find a nice flat parking area with a smooth wall. Park your car perpendicular to the wall, making sure your headlights are 20 feet from the wall. Use a tape measure to get it close. (I do mine at a local parking deck where there's a seam at exactly 20' from the wall. That way I know I've got the distance correct.) Also, you may want to mark the position of the car's wheels in case you have to move or need to readjust. I recommend a nice, quiet place where you won't be disturbed or have to move your car during the middle of the procedure. Some ambient lighting helps; just make sure that you can clearly see your low beams shining on the wall. Rock the car a little bit to settle the suspension. (No, this isn't what the assistant is for.) Put a small piece of masking tape in the very center of the windshield and the back window. (You are really more interested in the horizontal centerline than the vertical center.) You should be able now to stand behind the car and use the masking tape marks to spot a point on the wall where the exact vertical centerline of the car is aimed. This is where the assistant comes in handy. Mark this on the wall. (I use the tape and marking pen so the wall doesn't end up with H4 grafitti on it.) Now, back at the car, measure the height of the center of your headlights from the pavement. Also measure the distance between the two lights. Transfer these measurements to the wall, oriented about the centerline you previously marked on the wall. Make sense so far? You now should have marks on the wall that closely correspond to the positions of your headlights. Now, the actual aiming of the lights: Make a mark on the wall about 3.5 inches to the right and 1.5 inches below the point where your headlight marks are. This will give you the proper aiming points. Here's a ascii drawing of what you should have at this point on the wall. (As viewed from the front of the car.) mark on wall correponding to __ centerline of car | v + | + <- + are the actual lamp positions * | * <- * are the aim points right of | and slightly below the +'s | ------------------------------ <-- pavement Turn your lights on low beam. Now, have your helpful assistant stand in front of one light while you aim the other so that the point where the horizontal cutoff begins to sweep upward hits this point on the wall. After you've done the first light, aim the other to it's corresponding aim point. Take the car for a test drive. If they seem a bit outa whack, you can return to the aiming point and park in the exact spot (remember, this is why you marked where your wheels were located during the aiming process). You can also use this wall technique for aiming fog lamps or driving lights as well -- just figure out where you want 'em to be aimed relative to the actual light positions and have at it Happy aiming, Alex Little Raleigh, NC