How to perform a simple chassis alignment

A car can’t handle well if its wheels are pointed all over the place, right? That’s where properly aligning the chassis will help. The goal is simple: to maximize the grip of all four tires.

And how do you do that? Ideally with some testing-as we did with our Triumph TR3 vintage racer. A stopwatch and pyrometer will quickly reveal when the tires are happiest.

This kind of testing isn’t just for race cars, though. Autocrossing your classic? Looking to make it behave properly in the twisties? Think of these steps as a dyno session for the chassis.

FIRST THINGS FIRST

Before you attempt any testing, first put your car in the garage and inspect it thoroughly. Is the engine running correctly? Are there any cooling issues that need to be addressed? Is the oiling system up for a day of max g-loads? Trust us, the last thing you want to do is spend a test day chasing mechanical gremlins.

While brand-new tires aren’t required for this testing, you do need ones that are fresh enough to provide meaningful data throughout the session. This isn’t the time to finish off those corded, worn-out tires.

Once we had these basics covered, it was time to take our Triumph to the track. We conducted this test on the road course at Florida’s Gainesville Raceway. Though we rented the entire track, we resisted the urge to waste fuel and tear up tires and just focused on the figure eight part of the layout.

CHASSIS SETUP SUPPLY CHECKLIST

• A stopwatch or other suitable timing device.
• At least one other person to help check and record tire pressures and tire temps.
• A place to test the car-ideally a track, autocross course or other legal, controlled environment. A figure 8 that allows the car to reach about 60 mph is perfect.
• Basic hand tools to adjust chassis alignment.
• A pyrometer, camber gauge, toe gauge and caster gauge. (Race shops like Longacre and Summit Racing stock this kind of equipment.)

THE PROCESS

1. Before the test day, always change the oil, fill the gas tank, and go over the entire car, checking every fastener along the way. While inspecting our Triumph TR3, for example, we found a broken end link on our front anti-roll bar.

2. Thankfully, a quick call to Aurora had fresh, Teflon-lined rod ends heading our way. After comparing the new parts to the ones we installed when first preparing the car many years ago, we were stunned: The Aurora pieces looked and felt so much better. And, yes, we replaced everything on both sides of the car.

3. Although you don't need to test on new tires, you'll never get decent numbers on corded or totally dried-out rubber. If it looks anything like this, throw it out.

4. Our Triumph runs the 185/65R15 Hoosier Speedster, a vintage-looking radial designed for competition. We fit a new set of this test day since the old ones were finished.

5. Time to actually get on track. After setting our tires at 21 psi all around--our usual pressure--we ran a few warmup laps.

6. On a lot of older classics, a solid rear axle limits the alignment settings to zero camber and zero toe. Up front, though, camber, caster and toe are usually adjustable. Our TR3 runs about 1.5 degrees of negative camber up front. To achieve that much, we slotted our upper A-arms, allowing the tops of the spindles to be moved inward. To hold the spindles in place, we added these custom wedges.

7. Caster can be tweaked from side to side as needed. This stagger helps the car through turns. For the downtown Savannah race track, which features mostly left-hand turns, we add a bit more caster to the right: 2 degrees on the left, 2 3/8 on the right. Your stopwatch--and data system, if you're running one--will help reveal the correct answers here. How do we adjust caster? We run Jaguar XJ6 ball joints. They're similar to the Triumph pieces but are a little slimmer, meaning we can shim them back and forth by about an eighth of an inch.

8. This is our old-school toe gauge, which works well for comparing two reference points. On a relatively short track like Savannah, we set our TR3 with 5/32-inch toe-out for improved turn-in.

SETTING TIRE PRESSURES

We like to set our tire pressures first, using a method gleaned from Andy Hollis, a multi-time SCCA autocross national champion who often does the tire testing for our sister magazine, Grassroots Motorsports.

1. Inflate all tires to the same high psi estimate.
2. Time three hard, clockwise laps around a skidpad.
3. Drop the pressures by 4 psi all around.
4. Repeat steps 2 and 3 until the lap times point toward an ideal pressure range.
5. Note the range of pressures that produced the fastest laps.
6. Inflate all tires to the highest pressure in that range.
7. Time three hard, counterclockwise laps around the skidpad.
8. Drop the pressures by 2 psi all around.
9. Repeat steps 7 and 8 until you hone in on the fastest pressure.
10. Use a probe-type pyrometer to confirm the fastest pressures. Ideally the tire temperatures will be close to even across the entire tread. If they’re a little bit cooler on the outside edge, that’s okay, too. If the temperatures in the center are too high, though, the tire is running too much air. “When in doubt, trust the clock, not the pyrometer,” Hollis adds.
11. Tires cool as they sit, so waiting even a minute to measure a tire’s temperature can render the data almost useless. That’s why we recommend having at least one helper, so one person can take measurements on each side of the car. We record our data in an old-school notebook.

 

ALIGNMENT BASICS: CAMBER. CASTER & TOE

Negative Camber

Positive Camber

Camber: The lean-in or lean-out of a car’s wheels when viewed from the front or rear.
Goal: On most production-based cars, maximum negative camber is the correct answer-and you may have to slot, tweak or replace something to get a little more negative camber than stock. If the outside edges of the tires are getting too hot and thus wearing too much, your alignment likely doesn’t have enough negative camber.

Positive Caster

Negative Caster

Caster: The tilt of the steering pivot axis from vertical when viewed from the side.
Goal: The stock caster settings are usually pretty good, but if you can, adding a bit more than stock can help with high-speed stability.

Toe-in

Toe-out

Toe: The relationship of the two wheels on the same axle when viewed from above.
Goal: A little bit of toe-out up front can help with turn-in. Too much toe-out, though, can lead to instability, especially under braking.

Deeper Dive
Check out the December 2018 issue of Grassroots Motorsports for more alignment talk.

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