I can hear you saying, That's all great, but how do you know what rack shaft length you really need? "The rack shaft length should be the same length as the pivot points of the lower control arms," says Fred. "This is to keep the bumpsteer to a minimum." And, in fact, if you refer to Chart B, Fred provided us a list of the most popular chassis and their accompanying shaft lengths.
Taking out the old rack proved to be almost as easy as putting the new one in.
Chart A had given some ranges of recommendations and knowing that my old rack had been the wrong one all along, I got concerned about finding the right ratio for my driving style. Fred gave me an education. In general, ratio and "servo feel" is really more up to driver preference. Even so, there are some good rules of thumb to remember. Regardless of whether you're on dirt or asphalt, the ratio most depends on the length of the racetrack. On a small -mile track, a higher ratio would be needed. For example, if that little track was dirt, ratios would range from 3.9 to 4.4 while an asphalt one of the same size would be a 3.0 ratio. Incidentally, Appleton's 4.4 is the fastest ratio rack on the market. So, if you're running those quick little quarters a 4.4 could be perfect for you. Now, a long mile or sweeping track would require a lower ratio. A good dirt example would range between 3.4-3.7, while asphalt would require a range between 2.0-2.5.
But be careful, too fast of ratio on asphalt will cause an inexperienced driver to over steer the car or drive in an erratic darting motion. One other note, on dirt if you're one of those drivers who like to "back it in" you'll want a higher ratio in those ranges mentioned above.
The ratio, if you were wondering, is the distance that the rack shaft travels (in inches) with one turn of the steering wheel. The lighter (smaller diameter) the torsion bar, the more power assist you receive and the less effort to turn the steering wheel. Chart C below shows how the torsion bar weight/size relates to the steering feel.
Here we can see the difference between the two racks, note the adjustability of the new Ap
Install Time The installation of the rack-and-pinion is actually one of the easier things to do on a race car. In fact, we installed the rack in less than an hour and that included taking the old one out. With the old rack out of the way, we slid the new one into place, taking advantage of the adjustability to help clear the bottom of the radiator shroud. Three tightened bolts later and the next step was to hook up the hoses to the fittings. Appleton marks the two fittings with a "P" and "T" on the servo housing. The P represents the hose that goes to the pump, and the T is for the hose that goes to the tank. If for some reason you can't see the markings, the 45-degree fitting next to the rack boot goes to the pump and the 45-degree fitting closest to the U-joint goes to the tank.
Once the hoses are all hooked up, all you have to do is double check the fluid level and then turn the wheel back and forth several times, since the system is self-bleeding. You should have between 1,000 and 1,100 psi for the pump to run the rack correctly.
Troubleshooting The problem with our rack was pretty obvious, but sometimes potential problems are not so easy to diagnose. Here are some of the more popular questions that Fred gets asked from racers all across the country.
Q: If my servo valve is leaking can I buy a servo seal kit and fix it myself?A: No, if your servo is leaking out the valve, it has to be sent back to the manufacturer to be fixed because it has to be drilled and centered on the dyno machine. If it's not centered, it will turn one way or the other by itself.
Q: What would cause burnt power steering fluid in my steering unit?A: It could be either a bad pump or line causing burnt power steering fluid. Also, check the pulley setup on your pump. If the pump is a 6 inch, the crank should be 2 1/2 to 3 inches.
This may look really tight, but thanks to the adjustability of Appleton's rack design, it'
The new rack easily slides into position.
Appleton labels its hose hook ups with a "P" and a "T." The P represents the hose that goe