Wrench Tip: How to Do Your Own Alignment!

Now let me introduce you to my $4 slip/turn plates.

This is vinyl tile from home depot and a bottle of soapy water. The tiles costs $1 eachand come with an adhesive backing. Peel the paper off a tile, lift up the car and slap the adhesive side of the tile on the bottom of the tire. Then take the soapy water and thoroughly wet the smooth side of the tile, and also the floor where the tile is going to rest before dropping the car back down. Do this for all 4 wheels, and then jump on the car a couple of times to fully settle the suspension.

The tiles serve two purposes. Firstly, they act as slip plates. They prevent your tires from grabbing onto the ground as you adjust the alignment settings so that you don’t experience binding when you make adjustments. This effect also ensures that your suspension settles fully when you drop the car off the jack. Secondly, they are used as turn plates when measuring caster. This is possible because the adhesive makes the tile stick to the tire, which means the tile will turn with the wheel.

One thing worth mentioning is that I have epoxy floors in my garage. I believe this may be a large contributing factor to how effective the tiles are at introducing a frictionless surface under the tires. I doubt the slippery tile would slide as easy on asphalt. To combat this, I recommend you try 8 tiles. For every tile you stick on the tire, stick one on the ground under the tire, so that it will slide tile on tile.

The typical alignment order is caster->camber->toe. However, it’s not always that simple. For starters, you need a good toe reference to start off, or your caster and camber will be off. That means, if your toe is way off, you usually have to at least ballpark the toe before you can start doing the caster->camber->toe. If you know you already have a good alignment, and you just want to make tweaks, you can usually omit this step. Additionally, depending on your suspension setup, there are cases where camber adjustment can affect your caster, or toe can affect your camber, so you would have to go back and redo those settings.

But, let’s start with caster. Before you can measure caster, you have to know how to measure camber. Camber gauges can cost hundreds of dollars, but you can actually measure camber fairly accurately with just a level and a ruler. All you have to do is know the lip diameter, and some basic trigonometry.

Start by measuring the lip diameter of your wheels. Don’t just go by the specified diameter of your wheels. That number is actually the diameter of the tire bead seat, and is much smaller than the lip diameter. For example, my 18” wheels here actually had a lip diameter of 19 7/16”, or 19.4375”.
In order to measure camber, you essentially use the level to create a reference plane that touches the bottom of the lip and is perpendicular to the ground. Then you measure the distance between the top of the lip, and this new reference plane (the edge of the level). As you can see above, it’s easy to derive the camber angle from that measurement.
To take the measurement, rest the bottom of the level against the bottom of the lip. Now align the level until the bubble is perfectly in the center of the indicator, and measure the distance from the lip to the edge of the level. While taking the measurement, you have to make sure that the level is perfectly vertical across the wheel (so that you’re measuring straight down, not at an angle), and you also have to make sure that the ruler is perfectly perpendicular to the level. It’s very tricky trying to line up everything with only two hands. Use a friend, if you can.
I measured the distance from the lip to the level to be 1 15/16 in. Plugging that into our equation, we get a camber angle of 5.721. This is negative camber, of course. Make sure your calculator is set in degrees mode instead of radians!
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11 comments

  1. Thanks for the guide but I have a problem.

    I entered your shortened caster formula in Microsoft Excel, and got a totally different value.

    =ATAN((SIN(RADIANS(B64))-SIN(RADIANS(C64)))/(2*SIN(RADIANS(B65)))
    =0.05481679
    Instead of 4.2

    Reply

    1. ATAN in excel returns the result in radians by default. Convert it to degrees by changing your formula to =DEGREES(ATAN((SIN(RADIANS(B64))-SIN(RADIANS(C64)))/(2*SIN(RADIANS(B65))))

      Reply

  2. Great article and a very clear explanation of the string method for alignment but one query. You stress the importance of the bars being parallel to each other but presumably they don’t actually have to be square to the car – making a parallelogram out of the string and the bars is sufficient and they don’t have to make a rectangle. Would you agree?

    Reply

    1. This is correct, a perfect rectangle isn’t necessary. An isosceles trapezoid or parallelogram is okay. In either case, the string is spaced evenly from the hub cap on each side.

      Reply

    1. Do you know the tires won’t wear out in anything close to 25 miles even with the most extreme racing settings?

      Reply

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