When you make hard contact with the wall, or even bump wheels with another race car, you s
Ask any experienced driver and he's likely to tell you he depends on "feel" as much as his eyes to know what the race car is doing on the track. The mystical quality of feel is best described as input transmitted to the driver's body from the car. From his seat, the driver certainly cannot tell if the right-front spring is bottoming out or the rear tires are spinning on exit of the turns, but there's no doubt he can feel it. The driver can feel what the car is doing with his foot on the brake pedal, his rear end in the seat, and most importantly, his hands on the steering wheel. Elementary, right? Of course, but how concerned are you about how well your power steering box transmits information back to your, or your driver's, hands?
Properly setting up and maintaining your power steering system (both the pump and the gearbox) is critical in terms of fielding a car that's easy to drive, and also to eliminate the possibility of a critical failure on the track. A standard gearbox for a race car setup for a drag link steering system may seem like a pretty beefy piece of equipment, and it is. But the pitman arm, idler arm, and tie rods are designed to produce plenty of leverage to help the gearbox steer the wheels. That also means that if the front wheels make contact with the wall or another car, that same leverage is transmitted-often with damaging force-right back to the gearbox.
The valve and torsion bar fits inside the input shaft. If the pin that holds it into place
To get a better idea of how you can use your power steering system to improve the feel at the steering wheel as well, we traveled to Winston-Salem, North Carolina, to the shop of CJR Products. Owned by Ronnie Grayson, who started the business building boxes for Dale Earnhardt in 1988, CJR builds custom gearboxes and power steering pumps for several Nextel Cup teams, including Roush Racing, Hendrick Motorsports, and Richard Childress Racing. The shop also builds more economical units for the Saturday night racer at any level. It turns out that everyone in this four-man shop is a racer, and they understand the real-world economics of local, short-track racing.
Steering gearboxes are manufactured by Delphi. Racing gearbox builders like CJR purchase these boxes from Delphi and then rebuild them to its specifications. Much of the time and attention required is simply to make sure all the parts meet specs, but CJR does other upgrades to make the gearbox a more precise piece of equipment. One major option available to drivers is the "valving" in the box. This is a bit of a misnomer because the valve doesn't change, but the torsion bar on which the valve is attached does. This adjusts how hard the driver has to work to turn the steering wheel before the steering assist kicks in.
Here's a case of severely bent splines on the pitman arm. Still, despite the twist, you ca
The torsion bar actually slides inside the input shaft. One end is pinned to the shaft while the other is pinned to the spool cap. As the driver turns the wheel, he actually twists the torsion bar, moving the valve. Once the bar has twisted a certain amount, the valve is opened completely and the steering assist is activated. You can use different size torsion bars to adjust the amount of effort required to turn the steering wheel. Smaller bars twist more easily, requiring less effort from the driver, while thicker bars do the opposite. According to Jeff McBride of CJR, most short-track drivers prefer a 235 or 250 valve. The numbers represent the thickness of the torsion bar in thousandths of an inch (a 235 valve would mean a torsion bar that is 0.235 inch thick).
"The thicker bars mean the driver has to put more effort into the steering wheel," McBride explains, "but he also gets more feel for what the front end is doing. The lighter it is, the less the driver can actually tell what is going on-where the front wheels are. It seems the younger guys usually want the bigger torsion bars because they really want to feel with their hands what the car is doing. Older guys seem to want less because they have a more developed feel for what the car is doing, and they want to work less.
A hard hit can crack the teeth on the pitman shaft. The best check for this is to have the
"It is also interesting that the Cup guys generally want a bigger valve," he adds. "That's because they are usually running the bigger, higher-speed tracks and want all the feel they can get. They want to be able to tell whenever they dive off into the corner where the front end of the car is. But because they've got so much caster split in them now, the car will basically turn itself. That kind of gives them a false sense of feel, so you put a stiffer valve in it, and that way when they go into a corner, they can still feel where the car is."
The second variable in a gearbox is the ratio. The standard Saginaw gearbox produced by Delphi is available with several different ratios. They are 12:1, 14:1, 16:1, 17.5:1, and 20:1. The ratios are for the input shaft versus the output shaft. For example, a 12:1 gearbox would require 12 turns of the steering wheel to make the output shaft, or pitman shaft, make one complete revolution. Of course, you are never going to turn the steering wheel 12 times or want the pitman shaft to make a complete revolution, but this gives you a good idea of the steering rates. Generally, faster rates are used on tighter tracks while the slower rates are used at bigger tracks where less steering input is necessary. The 17.5:1 and 20:1 ratios are normally only used at monster tracks like Daytona and Talladega.
Still, even if you are racing each week on a tiny bullring, you may not want to depend entirely on a 12:1 ratio because it is the fastest. "We are noticing a trend of weekend racers on the shorter tracks going from a 12:1 to a 14:1 ratio," McBride says. "They don't race as much as the Nextel Cup drivers do, and they sometimes get a case of happy hands, or jerky in their reactions. The 14:1 ratio slows down the car for them. It keeps them from jerking the car around too much and makes it more driveable for them."
The pitman arm on the left is good, and the one on the right has been damaged in a wreck.
Your steering linkages need to be set up so that the gearbox is centered when the wheels are pointed straight ahead. That sounds like common sense, but it is easy to miss. There are a few ways to determine the center in the steering box. First, there is a hard spot that the driver can feel when he turns the wheel. This can actually be distracting to a lot of drivers, and if this is the case with you, tell your box builder you want the hard spot reduced. The second way is to notice the large flat on the input shaft. When the box is properly mounted, that spot should be facing upward.
Finally, you can check it manually. With the box connected to the steering shaft, turn the steering wheel fully to the left. Now, turn the wheel back to the right. The second time the flat spot on the input shaft comes up (you should be able to see it behind the coupler), that's the center. This is true for every ratio except 17.5:1 and 20:1, in which case it is the third time around.
In some cases, drivers that don't like to feel the hard spot in the center of the steering box will have the toe on both front tires moved slightly to the right by a degree (the left-front will have less toe-out and the right-front will have slightly more than normal). Now when the steering wheel is straightened up, the gearbox is set so that the driver will not feel the hard spot unless he or she turns to the right. This doesn't cause a problem, except the valve is now cracked open a small amount. When this happens, fluid pressure is trying to push it closed while the driver is holding it open, and this causes the power steering pump to work harder. This translates to a small amount of horsepower. Again, the best solution if your driver dislikes the hard spot that marks the center of the gearbox is to ask the builder to reduce it.
CJR has developed this fixture to quickly check a pitman arm. If it has any malformation,
This view looks at the part of the gearbox facing the firewall. The flat on the input shaf
Jeff McBride checks a new gearbox on CJR's steering dyno. This ensures that the gearbox wo
Many power steering pump pulleys are fitted to the input shaft on the pump with interferen
Unless you are familiar with the critical tolerances of a steering gearbox, it's probably not a good idea to break one open yourself for regular maintenance. CJR recommends you send your gearbox in for a thorough check every 1,000 miles. For a Nextel Cup team, that's a single race weekend, but for a Saturday night racer, that's probably an entire season of racing. You can note that 1,000-mile mark if you haven't banged up the car. The biggest cause of problems is front-end damage to the car. Anytime you have banged wheels hard or been in a wreck that caused the front end to get tweaked, it's probably a good idea to send your box in for a checkup.
There is a visual inspection you can do yourself. Look for cracks in the housing or bent splines on the input or pitman shafts. To get a good look, you'll probably need to take off the pitman arm. While it's off, check it for damage, too. Besides cracks, the most common sign of damage on pitman arms is in the main coupling to the pitman shaft, which will be stretched into an egg shape. The arm itself can be twisted, so lay it on a flat surface to check for a torsional twist. You will want to have a professional check the rest of the system. CJR recommends magnafluxing everything to find cracks before those cracks become dangerous. The last thing you want is a failure that leaves you without steering.
One final note: The latest trend in race car setups is the soft front spring/big sway bar package. When done correctly, the setup works, but a lot of racers don't realize how many things can be affected when you cut your front spring weights in half. The car rides a lot lower, and parts that normally have plenty of clearance are now scrubbing the track. On the front of the car, the pitman arm is often the first thing to hit the track. Be very careful if the bottom of the pitman arm looks like it has met up with a grinder; it's rubbing the track, which can cause serious damage pretty quickly. If this is the case, you may need to make some modifications to your front clip to raise the gearbox up a bit.
It's a pain to send your pump to the manufacturer anytime you want to change the pulley, s
The mistake most often made with power steering pumps is over-spinning them. Jason Fletcher, who builds all the pumps for CJR, says you can save some serious power by not working your power steering pump any harder than you have to.
"Pumps usually have enough flow by 1,500 rpm," he says. "If you exceed 4,000 rpm, you are just wasting your power because, after that, they go into bypass mode. We've had some racers who think that if they spin the pump faster they will get more pressure, which will help driver feel. That's just not true. Divide the diameter of the main pulley by the diameter of the pulley on the pump, and then multiply that number by your racing rpm. If you are in that zone between 1,500 and 4,000 rpm, then great. If not, you need to adjust the size of the pulley on the pump."
Also remember that, like engine oil, power steering fluid breaks down with extended use and heat. At a minimum, you should flush the power steering system once a year and replace it with fresh fluid. CJR recommends using a DEX 3 transmission fluid for its exceptional properties.
Soft spring/big sway bar suspension packages are gaining popularity, but be careful when t
This example isn't quite as extreme, but you can tell from the bottom of the pitman shaft
Power steering pumps are gravity-fed from the fluid reservoir, so always make sure the res