RetroRacing’s Autocross Adjustment Prep

Lesson 4: Getting Adjusted

Remember, quick cars (as opposed to fast cars) have the advantage in autocrossing. That's because top speed and high-speed stability and braking don't matter. A hot autocross car is prepped to act and react suddenly. You want sudden acceleration, gear change, braking and steering.
Presuming you have an absolutely stock VW Ghia or Bug, and you recall our tips on tire pressures from last time, there are several key adjustments to be made.

Adjust your clutch so that you have a half-inch of pedal freeplay. You don't want too "loose" (the common street condition) a clutch, meaning too much pedal freeplay. You want the clutch to respond instantly, like a hair trigger on a pistol. Check your clutch pedal arm to see if its cracked (they do crack) or bent, and if the clutch pedal stop is working. Under stress, a cracked arm will cause enough play to keep your clutch from disengaging, especially when you are stomping it like you will be.

Adjust your accelerator cable clamping at the carburetor so that when your gas pedal is on the floor, you really have 100% throttle. Look at the throttle plate and make sure when you are depressing for full throttle, it is open, straight up and down, and not off to either side. When you check the cable connection, make sure the gas pedal hinge itself isn't bent so the pedal leans to one side, and the gas pedal roller lever under it isn't bent. VW accelerator pedal assemblies are infamous for bending over time.

Adjust your carburetor accelerator pump to give the best acceleration. The stock VW single Solex carbs have adjustable pump strokes. Generally speaking, slightly increasing your pump stroke will give you a bit more gas on takeoff, and that should mean better acceleration. Too much or too little stroke, and you'll create hesitation. It's a cut and try operation, but it's easy. You can help out the acceleration with a little timing advance over stock, too. But just a little, usually no more than 10° BTDC. And after the race, reset back to stock. Dual carb setups and different types of distributors can all benefit from this same advice, but you'll have to find your own sweet spot.

Adjust your brakes. For autocross, you want firm brakes, and instant response. Adjust the drums just so one or two more clicks tighter would cause scraping as you rotate the wheel. Since we don't adjust discs, on Ghia's the rear drum adjustment is how you set brake pedal feel. Note: For road racing, you back off the drum brake adjustment more than you would for autocross, to prevent brake lockup once the fluid is hot and some expansion has occurred. Luckily, autocross doesn't overheat your brakes.

Adjust your steering play. By the book, you're supposed to have about one inch of freeplay at the steering wheel with the tires in the straight-ahead position. Jack up the front of the car so both front tires are off the ground, and turn the steering wheel all the way to either side. Tighten the adjusting screw on the steering box only a fraction of a turn at a time, between freeplay checks. To check, spin the steering wheel back to straight ahead. Gently rock the steering wheel back and forth as you watch the wheels. If you have one inch of freeplay and no wheel movement, you should be okay. Test drive the car, turn a sharp corner and briefly let go of the steering wheel. It should swing back to straight ahead, or almost straight ahead. If it doesn't, you have it too tight.

Next time: Driving It