If you are like me sometimes you overlook the obvious while in hot pursuit of the glitzy, cool (expensive) stuff. Front end alignment is one of those obvious things that seem so mundane that why bother? In some ways it’s a trip to the alignment shop is like a trip to the dentist to get your teeth cleaned. Besides that it seems like some alignment shops are more interested in selling you things you really don’t need so why go? We will look at the benefits and some tweaks which can be done with the front end alignment that will pay off in a better handling car.
Factory specs for alignment are established as a trade off in tire wear and better handling. This is because of some basic geometric principals like camber, covered later, which can improve how your car “feels” can cause more than normal tire wear. It is all about the kind of driving you want to do. If you are a boulevard cruiser and corners are not of interest then probably the factory settings are close but no where optimum. With that said, things have radically changed in tire profile since our classics were new which may mean you might want to revisit the factory settings.
Let’s look at the alignment settings for a typical classic car’s front suspension and see what they do.
This is what makes shopping cart wheels run straight. This is illustrated in the figure. As you can see the steering pivot is in front of where the wheel contacts the ground in the direction of travel. This forces the wheel to always track straight when the cart is pushed forward or backward without wandering. (Depending on how beat up the shopping cart is.) The same principal applies to the front end of most rear wheel drive cars.
The factory usually sets the angle near zero depending on the vehicle. This was fine when they ran those skinny balloon tires in the good old days. Today the contact patch, the “foot print”, of the tire where it touches the road is much larger. Leaving the caster at or near zero will cause the car to wander and the steering to not want to return to center after a turn. This is because the contact patch is so much bigger on modern tires and no opposing force to “caster” the wheels straight like a shopping cart wheel. With positive caster (tipping the steering pivot angle toward the back of the car) the wheel now has a force ahead of the contact patch to align the wheel in the direction of travel.
This is the “tip” of the wheels as viewed from the front. Negative is inward tipping of the top of the wheel; positive is outward tipping as shown in the diagram. Negative camber is preferred since it will counteract the geometric tendency for the suspension to lift the contact patch as the body rolls during cornering. This setting can have the most dramatic impact on the cars ability to hold front end traction in a corner. It also can cause the most uneven tire wear over time. That is because the inside edge of both tires are loaded higher than the outside causing them to wear more.
The factory setup opts for zero to positive camber to keep the car in an understeer setup. This makes the front end tend to “push” or “wash out”. The factory lawyers like this because novice drivers are less likely to have the back end come around if they aggressively make a turn. It results in decreased traction and a slower turning car.
This setting is the angle of the front wheels as viewed from above. Toe is determined by measuring the distance between the track of the wheels in front and in back. It can be toe out or toe in depending on how it is set. This setting is influenced by ride height. A car at high speed can have appreciable changes in the toe setting as the suspension is loaded by the aerodynamics of the car. Most cars are set with toe in.
Here is a chart of suggest settings depending on your driving preferences. These are just starting points. In order to set them to optimum you will need to do some experimentation and determine what is best for your car.
|Touring||0.25 to 0.5 Deg neg.||2.5 to 5.0 Deg pos.||0 to 3/16″ In|
|Autocross||0.5 – 1.0 Deg neg.||2.5 to 5.0 Deg pos.||1/8″ Out to 0|
|Road Racing*||0.5 – 2.0 Deg neg.||2.0 to 7.0 Deg pos.||0 to 3/16″ In|
There are many variables to work with but the key is to make the adjustments and systematically measure performance improvement. The results will be a car that is dialed in for the type of driving you do, not what the factory decided you might do.