Front End Alignment

If you are like me sometimes you overlook the obvious while in hot pursuit of the glitzy, cool (expensive) automotive stuff. The front end alignment is one of those obvious things that seem so mundane that we say “why bother? ” In some ways it’s a trip to the front end alignment shop is like a trip to the dentist to get your teeth cleaned. It seems like some of those front end alignment shops are more interested in selling you things you really don’t need. We will look at the benefits and some changes which can be done with the front end alignment that will pay off in a better handling vehicle.

Manufacturers specifications for alignment are established as a trade off in tire wear and better handling. This is the results of some basic geometric principals like camber, covered later, which can improve how your vehicle “feels” and can cause abnormal tire wear. It is all about the kind of driving you do. For instance, if you are a boulevard cruiser and fast cornering are not of interest then probably the factory settings are close but in no way optimum. Tires have radically changed in profile since our classic hoops were new which may mean you might want to revisit the factory settings.

Let’s look at the alignment specifications for a typical classic vehicle’s front suspension and see how they operate.

Caster

This is the consept that makes shopping cart wheels run straight. Observe the steering pivot is in front of where the wheel contacts the pavement in the direction of travel. This makes the wheel always track straight when the cart is pushed forward or backward without wandering. The same principal applies to the front end of most rear wheel drive vehicles.

The manufactures usually sets the angle near zero depending on the vehicle. This was acceptable when they ran those skinny balloon tires in the good old days. Now the contact patch, the “foot print”, of the tire where it touches the road is much larger. Having 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 larger on modern tires and no opposing force to “caster” the wheels straight like a shopping cart wheel. Using positive caster to tip the steering pivot angle toward the back of the car will give the wheel a contact force ahead of the contact patch to align the wheel in the direction of travel.

Camber

This is the “ inclination” of the wheels as viewed from the front. Negative is inward tipping of the top of the wheel; positive is outward tipping. However, negative camber is preferred since it will counteract the geometric tendency for the suspension to lift the contact patch as the vehicle rolls during cornering. This setting can have the most dramatic impact on the cars ability to maintain front end traction in a corner, but it also can cause the most uneven tire wear. This is because the inside edge of both tires are loaded higher than the outside causing them to wear more.

The manufactures setup opts for zero to positive camber to keep the vehicle in an understeer situation. This makes the front end tend to “push” or “wash out”. The manufacture’s lawyers like this because novice drivers are less likely to have the back end come around if they aggressively make a turn. This results in decreased traction and a slower turning vehicle.

Toe

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.

Next Step

Here is a chart of suggested 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.

USE CAMBER CASTER TOE
Touring 0.25 to 0.5° negative 2.5 to 5.0° positives 0 to 3/16″ Toe In
Autocross 0.5 – 1.0° negative 2.5 to 5.0° positive 1/8″ Toe Out to 0
Road Racing 0.5 – 2.0° negative 2.0 to 7.0°positive 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.

Note: For street tires, R compound and slicks require significant negative camber. Follow the tire manufacturers recommended alignment settings.


This article is the intellectual property of Simmons BOSS CREATIONS. Any reuse of the contents must include the following attribution:

Marcus Simmons, ASE Certified
Simmons BOSS CREATIONS
Phone: (248) 461-6977
Email: ceo@simmonsbosscreations.com
http://www.simmonsbosscreations.com