Setting Things Straight

Of all the chores associated with street-rod maintenance, one of the most neglected could well be frontend alignment. It's one of those things that none of us pay much attention to; that is, until the car seems to have a mind of its own and wanders all over the road or the tires develop a funny wear pattern and the corners of the treads are knocked off.

Once it's obvious that the frontend of a street rod needs alignment, the challenge you may be faced with is finding someone to do it. We've been turned away from alignment shops for a variety of reasons--everything from they didn't do specialty vehicles without published specs to the car was too low to get on the rack. Then there was a case where, in retrospect, we wished we had been turned away. By the time a well-meaning but ham-fisted technician was done with one of our cars, there wasn't a painted or plated suspension component that wasn't scarred. And that was after waiting a week for an appointment. This isn't to say there aren't alignment shops that do a great job on street rods, there are. But an overlooked option is doing the job yourself.

While aligning a frontend at home might seem intimidating at first, it's actually quite easy with the simple, available equipment we're going to show here. But before we get into that, let's talk about some terms you'll need to be familiar with.

Camber
Camber is the tilting of the wheels from vertical. Positive camber means the top of the wheel leans out. Negative camber is the opposite; the top of the wheel leans in and the amount of camber is measured in degrees from vertical.

Caster
In addition to being tilted toward the center of the car, the steering axis also leans towards the front or rear of the car. Forward tilt is negative caster, rearward is positive.

Most cars use positive caster because it prevents road wander and helps keep the wheels pointed straight ahead (drag race and Bonneville cars often use extreme caster for high-speed stability). With positive caster the weight of the car rests behind the tire's pivot point on the ground. So, just like the casters on a shopping cart, as the vehicle moves forward, the wheels want to go straight.

Toe
The distance between the front and rear of the tires is called toe. Most cars use a small amount of toe-in (the front of the tires are closer together than the rear).

Toe-in is used to compensate for the cumulative effect of all the tolerances in the steering system. Without a bit of toe-in when the car moves forward, any slack in the various steering would let the front of the tires spread apart, resulting in toe-out. Toe-out will cause most cars to wander when going down the road.

A good indicator of proper toe setting is tire wear. While it's not very scientific, run your hand across the tire's tread from the outside in, then the inside out, and feel for sharp edges. If a sharp edge is felt from outside in, it's an indication that more toe-in is required. If a sharp edge is felt going from inside out, more toe-out is needed. Of course, if the treads feel about the same from both directions, the toe is just right.

One last thing you should be aware of when setting toe is it can be changed by adjusting caster and/or camber, but adjusting toe will not the other way around. For that reason, toe should be set last.

Adjustments
When solid axle suspensions were the norm under production cars, they usually had a certain amount of positive camber. As examples, early Fords called for 1/4 to 1 degree, Chevys 1/2 to 1 1/2 degrees, and Mopars 1/4 to 3/4 degree. And while those figures are still valid, most contemporary radial tires generate the most cornering force with a trace of negative camber, around a 1/2-degree. So how much camber should your street have? Most aftermarket axles will use factory specs, and that works fine. But the truth is the axle will decide camber, and you won't be able to do much about it at home other than check it.

Changing camber of a solid axle requires bending, a task that is still done regularly on trucks and can be done to a stock or dropped OEM axle. However, with aftermarket axles, the smart thing is to check with the manufacturer for their recommendation if camber is outside of specs.

Depending on the design, independent suspensions systems may have positive or negative camber when the car is static. Early Mustang II frontends ('71-'73) used 1/2-degree negative, while the later ('74-'78) used 1/4-degree; that's an acceptable range for most street rods, too. If you're using a custom IFS, consult the manufacturer for alignment specifications, but in any case, keep in mind that as the suspension compresses and rebounds, camber of an IFS changes. Most contemporary independent suspension systems are designed to gain negative camber on the outside wheel and positive camber on the inside as the car leans in a corner, so it is critical that the car be at ride height when any adjustments are made. Adjustments are usually made to street rod-style frontends by moving the upper control arms in or out.

Although most early cars with straight axles used positive caster, the amount varied. Ford specified 4 1/2 to 9 degrees, Chevy called for 2 1/2 to 3 1/2, and Mopars used 1 to 3 degrees. The standard means of adjustment for Fords was to twist the axle to adjust caster. Cars with parallel leaf springs up front (then and now) can use tapered shims between the main leaf and axle. With most Ford-based street rod applications, adjusting the caster is done with the radius rods.

By comparison to an early Ford solid axle, most street rod independent suspensions use less caster--Mustang frontends typically require 2 to 3 degrees. Again, check with the manufacturer for custom frontends, and adjustments are usually made with the upper control arm.

The last thing to be adjusted on any frontend is toe-in. Both independent and solid axle frontends will usually be set with 1/32 to an 1/8 inch of toe-in (early Fords were set at 1/16 to 3/32 inch, Mustang IIs call for an 1/8 inch). Toe adjustments are made with the tie-rod ends for both solid axles and independents, but before any changes are made, make sure the wheel bearings are properly adjusted and the steering gear is centered in its travel.

So, What Do You Need?
Basically, the equipment required for home alignment is a caster/camber gauge and something to measure toe.

Caster/camber gauges for home use range from simple to exotic, and, as you might expect, prices vary accordingly. We tried three examples from Speedway Motors, the $28.90 econo model, $110.90 magnetic version, and the $269.90 digital unit. All three did the job admirably. The econo unit is a bargain, the magnetic tells you everything you need to know at a glance, and the digital is quick and easy to use. Of course, which is appropriate for you depends on the budget and how often you plan to use the equipment. Also shown are Speedway's toe gauge that goes for $72 and Heidt's toe adjustment kit that sells for $35. Again both do the job effectively.

Aligning your street rod at home is easy to do, and the cost of the equipment required can be recouped by doing it yourself just a few times. Best of all, no appointments will be necessary.