Toe-in

By Jon Belanger

It's been awhile since we've looked at chassis setup and it's probably time to put a wrap on the series with the discussion of toe settings. Let's start with the front because it's easier and less controversial.

Front toe-in is normally set as close to "0" as is practical with the range running from 0-1/16". The idea here is to incur as little tire scrub as is possible. Although with some Vees the play in the rod ends, link pins, and other assorted front end parts can cause toe-out during hard braking and should be compensated for with up to 1/16" of toe-in. To do this, first scribe the circumference of all four tires. I use a center punch, but an extra-fine marker would work just as good... don't use chalk as the line is simply too wide to be useful. Then, air the tires and settle the car (at race weight) on a nice even surface. Now, using a toe-in gauge, check the distance from scribe mark to scribe mark on both the leading and trailing sides of the front tires. Taken at the height of the centerline of the wheels these readings will give you your toe-in (pointed in at the leading edge) readings. For more toe-in simply lengthen your tie rods and shorten them for less toe-in. When you're all finished make sure your steering wheel and steering box are still both centered.

Next up is the rears. This is slightly more difficult for a couple of reasons. First, you want to make sure the rear wheels are square to the car to prevent it from "crabbing" down the track. I've seen some experienced racers chasing this around with dozens of measurements, taken from a million different points... none of them really adding up to diddley! It's important to remember that these are Vees, not Indy cars, and some of our chassis were as much as a few sixteenths out of square right from day one. With this in mind I always start out by getting the distances from my rear axles to the top shock tower bolts equal. Then I dial in between 0 and 1/16" of toe-in by adjusting my trailing arms. Here's where it gets really tricky... most people divide the toe-in by adjusting my trailing arms... most people divide the toe-in equally between the rear wheels and this works fine. But several years ago Jerry Knapp (of the original Laser fame) did a bunch of testing and decided it was quicker to put all the toe-in into the left rear to help the car get around right handed corners. Now I've argued this with everyone from National drivers to backyard theorists and one thing's sure... no one agrees. It seems that two years ago Benetton used its four-wheel steering to achieve this same effect in corners. To quote, "On slow tracks, the rear wheels steer in the opposite direction to the car to improve turn-in; while on fast circuits, where it is better to have a car with slight understeer, it is likely that the rear wheels steer in the same direction as the fronts to improve traction at the back of the car."

Well, you be the judge. Just remember these few points: Never toe-out the rear wheels because it causes the car to become twitchy and a nightmare to drive and more rear toe-in tends to create understeer and causes tire scrub while less rear toe-in tends to create oversteer.

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