Adventures in Alignment
Part 2
Last month I attempted to impart some small understanding of the mysteries of front-end geometry and of the terminology which is often casually tossed around whenever gearheads and bench racers gather. Now a true life adventure.
After the installation of the Turbo style tie rods on my SC it was time for an alignment. I scheduled the work and went in armed with the factory specifications and an idea of what I wanted, namely more negative camber. The objective was also to maintain a differential in negative camber between front and rear, and to get as much negative camber as was reasonably possible without modifications or severely shortening tire life.
The tie rod installation really threw the front-end geometry out of whack. Negative camber was -0.1 on both sides, toe was 1.38 and -.0.04. Rear camber was near spec at -0.9 and -0.8. Rear toe was 0.13 and 0.21. The first shot resulted in zero toe, as called for by the little white spec book. We took negative camber to -0.6 and -0.5 in the front and -1.5 in the rear. Rear toe was set at .03 and .02.
On the road this set up was not at all satisfactory. The SC turned in nicely, but at speed there was no feeling of stability at all. Scary would be a good word for it. So it was back to the shop for another try.
This time we pushed negative camber as far as it would go, to -.09 and -0.8. at the front and -1.5 and -1.7 at the rear. We also added a slight bit of toe in the front which Denny at Layland noted would improve stability at speed: just a nudge at .02 on both sides and 0.10 and 0.11 at the rear. The result of these settings was remarkable. High-speed stability was great due to the slight slip angle which the front toe settings created and turn-in improved with more negative camber.
The lesson? The first was that the factory specifications were OK for just average street driving, but more aggressive driving requires suspension geometry to match. Second, you do not have to go very far to significantly improve, or significantly screw up, the way the car feels.
Another lesson was the importance of the conditions under which the alignment was performed. Even minor changes in weight or weight distribution can have a dramatic effect on the results. Just opening a door while the alignment machine was giving its digital read-outs showed marked changes in the settings. So, on the last effort I sat in the car, thus simulating the most common condition on track or during aggressive street driving (no one wants to ride with me, and I don’t know why).
So the recommendation for you is to start with your factory specs and then get as aggressive with the settings as you can without ruining the car for other purposes. It is also recommended that you have a half tank of fuel and have weight in the car which simulates the most common conditions for the situation in which the settings are to provide optimum handling. Some shop manuals call for specific weights in different parts of the passenger compartment, but it makes more sense to me to try and match the conditions in which you will push the car the hardest.
© W. S. Cline/ Rose Lane Garage 2000