Introduction: DIY Precise Alignment (Toe-in)

About: I'm a machine designer for many different industries. I've been around mechanical things and manufacturing my entire life. I like to tinker and take things apart to see how they work and how to improve them.

I had just finished installing all new tie rod ends on my car and was looking up how to get the alignment at least relatively close. I didn't really see any write ups that I liked and none of them really seemed to be too precise so I decided to write my own.

Step 1: What You'll Need to Align the Car

Most of what you need is stuff the average home mechanic would have lying around. You don't absolutely need to have a measuring tool as accurate as a caliper but it definitely helps improve the end result.

1. Jack stands (2)

2. Some sort of string (I used fishing line)

3. 2 moderately heavy objects (I used 2 large impact sockets I had)

4. A caliper with the ability to measure depth

5. About 45 minutes to set up and do the alignment

6. Some wrenches to adjust your tie rods

7. Some sort of scientific calculator. It can be an app on your phone or a dedicated calculator. As long as it can do angle calculations you'll be fine.

Step 2: Set Up Your Car

Park your car on a flat, level surface with your steering wheel centered. Don't jack it up at all or do anything to shift the suspension. Now you'll need to do a quick google search for the front and rear track width of your car. I found that my car had a front track width of 57.2" and a rear track width of 56.8". The track width is the width of your car between the wheel hubs. This gave me a difference of 0.4" overall or 0.2" on each side. Now you need to set up 1 jack stand at the back of your car, on the side behind the rear wheel and the other jack stand in front of the front wheel and off to the side. Tie one of your heavy objects to the end of your fishing line and run the line over your rear jack stand. Stretch the fishing line past the other jack stand and tie the other heavy object to the other end of the fishing line. Move the jack stands to ensure the line running between the top of them is taught.

Step 3: Align the String

Now, using the difference between the track width align the string. Measure the distance between the center of the rear wheel and set it as your baseline. Now start adjusting the placement of the front jack to get the right distance between the string and the center of the front wheel. My front track difference was 0.2" (5.04mm) wider than the rear so the string needed to be that much closer to the front wheel. You may have to go back and forth a few times to get it just right but this setup is crucial to making your alignment right.

Step 4: Adjust Your Front Toe-in.

Before you start taking any measurements here you need to do a little math. Look up your cars specific alignment specs online. I found my car's toe-in spec was 0.14 degrees on each side. Now you need your car's wheel diameter. In my case it was 15" or 381mm. Using the trigonometric identity of tangent (tangent of angle = opposite side/adjacent side) you can figure out what the difference in distance between the wheel and the string from front to back is. I decided to shoot for a toe-in of roughly 0.12 degrees as I wanted a little less toe-in. I came up with tan(0.12 degrees) = max distance/381mm or max distance = tan(0.12)*381mm = 0.8mm. This means that the front of the wheel should be about 0.8mm farther from the string than the rear of the wheel. Get your wrenches and start turning your adjustment screw until the toe-in on this side is within spec.

Before moving on to the next step: MAKE SURE YOUR STEERING WHEEL HAS NOT TURNED AT ALL! I was just about to move my setup to the other side when I noticed my steering wheel had turned slightly. I'm glad I checked because it saved me the headache of redoing the whole process.

Step 5: Move to the Next Side and Repeat the Process

Now take down your setup and move it to the other side of the car. Repeat the adjustment process for that side.

Now you are done, enjoy your newly aligned car. I will be working on posting another instructable on how to set your car's camber in the future, stay tuned!