Ask any racer what steps to take when installing a steering system and they'll probably give you a squint-eyed, "What?" before you can say duh. That's because most racers treat the installation of the steering system the same way they treat installing a set of tires--just bolt them on and go. But the truly knowledgeable, and probably winning, racers know this question requires a very involved answer that is heavy in details. To learn more about this black art of getting your race-car steering system installed and ready to steer you to the front, Circle Track checked in with the knowledgeable and outspoken Randy Sweet, of Sweet Manufacturing in Kalamazoo, Michigan, and the chassis specialists at Craig Raudman's Victory Circle Chassis in Bakersfield, California. We doubt you've seen a lot of this steering technology before, but you can plan on seeing more details on this applied to other race cars in Circle Track. We think you'll find using the steering system to get around the racetrack quickly interesting.
The purpose of the steering system on a circle-track car, whether it be pavement or dirt, is to transmit the steering inputs of the driver to the front wheels. The steering system should exhibit good Ackerman geometry while the wheels are being turned and minimal bumpsteer while the suspension is going up and down.
To make sure we're all on the same page, Ackerman is a steering design that causes the inside wheel in a turn to receive more steering angle than the outside tire. This is done because during a turn, the inside wheel travels in a tighter radius than the outside wheel, so to prevent dragging one of the front tires through the turn, they are turned at different angles. Bumpsteer describes the steering input the wheel sees, while the steering wheel is held steady, as the suspension moves up or down. This input is due to the different arcs being swept by the different-length lower suspension A-frame and tie rod. If this is just the least bit confusing, understand that people have dedicated their lives to understanding suspensions, and we still learn new information every day on how to make suspensions work.
Most racers are familiar with this technology and spend a lot of time getting the steering to do these tasks but, according to Sweet, they are missing one very important aspect of the steering system's job. The front wheels can never, ever, attain toe-in--front tires pointed in toward each other--especially when a car is entering a corner. While practically every circle-track racer known sets their front wheels with about 1/8 inch or more of toe-out, there are times on the race-track where the wheels will toe-in. This is bad as toe-out works best for the front suspension, steering geometry, tire deflection, and other components on circle-track cars to let the driver steer the car around the corners quickly.
Toe-in does everything to a race car you don't want to have happen. It makes the rear end want to come around the car just about every place on the track--entering the corner, exiting the corner, everywhere. This story will show you how to determine if you are getting toe-in (Sweet thinks there are plenty of racers with this problem) and how to get rid of it while you learn some other great tips on how to get your steering system doing its best.
Does this look like a bunch of guys installing a steering system? Probably not, but it is. Randy Sweet, (right) uses this trick little measuring apparatus to determine if the Ackerman is correct throughout the turning motion of the wheels. You would be surprised how many cars have bad Ackerman, which is why they don't handle in the corners.
A complete steering system for a Late Model stock car consists of a rack-and-pinion unit, power-assist servo, U-joints, couplers, pump with pulley, pump bracket, pump reservoir, power-steering fluid, spindles, and a steering wheel with a coupler from Sweet Manufacturing. The hoses and fittings are from Goodridge in Torrance, California. The upper and lower A-arms are from Victory Circle (VC); the rod ends are from Alinabal, in Milford, Connecticut; and the swedged tubes are from UB Machine, in New Haven, Indiana.
The first step to installing a Late Model steering system is to find the center on the rack-and-pinion so that the housing can be installed centered up in the race car. To make this job easy, Victory Circle's Tracy Norman welded a used up 9/16-inch socket to a Sweet 49 spline coupler to turn the shaft on the rack. This rack took two full turns lock-to-lock, so the shaft was turned one rotation and a black line drawn lengthwise on the shaft with a marker pen to indicate it was centered.
While most racers just bolt on their rack and other pieces and go racing, Sweet recommends you locate all the pieces so that both wheels point straight when you get the system centered up and everything stays that way once you hit the track. Along those lines, Sweet dislikes the slotted rack mounts on most chassis because they're too flimsy, allowing the racks to move around. He boxes them on the bottom on his race cars. At the very least, Sweet recommends welding some thick washers, like these shown (above right), under the mount once the rack has been located so that if the rack needs to be replaced in a hurry, it won't throw off all the steering geometry. He also says that "lock washers are for farm vehicles" and that all the fasteners on your steering system should be held in place with "blue" Loctite threadlock or safety wire.
To center the rack in the chassis, both Sweet and VC recommend using two 1/2-inch-diameter pointers (VC machined a point on 6-inch-long 1/2-inch-diameter bolts in a lathe) that are installed through the lower locating arm anchor bolt holes in the chassis. On almost all chassis, these bolts will be equidistant from the centerline of the car, though one might be higher than the other (usually the driver's side). This different height would signify a nonsymetrical front suspension--more on this later. Using a carpenter's square, the center of the rod-end bolt holes on the rack are lined up with the anchor bolts and each end positioned until it is the same distance from the frame. When this is achieved, snug the rack mounting bolts.
The next step is to get the left-front wheel pointed straight. The frame must first be set at ride height, in this case a set of blocks is used under the frame, and the suspension needs to be blocked at ride height without the wheels/tires on the car. Once this is done, the first step to getting the wheels pointed straight is to get a string lined up with the centerline of the car. The VC chassis has the left-side framerail parallel to the centerline.
Then, a large carpenter's square or plumb bob is used to get the rotor an equal distance from the string in front and behind the spindle centerline. When this is achieved, the spindle is pointed straight ahead. As a note, this is done with the rotor instead of the Bassett wheels and Goodyear slicks being used here for a few reasons. First, they get in the way of the measuring that is to come after this step and second, Sweet only trusts the brake rotor for being "true" (tires do have some sidewall runout due to mold shape and the plys ending).
Without moving the rack position, the UB Machine swedged tube with Alinabal rod ends is bolted onto the rack and adjusted until it's the proper length to mate with the "straight" spindle mounting hole. Notice that the spindle mount for the steering arm can be adjusted front and back--that is to change the Ackerman, which is a critical tuning tool for a changing racetrack, especially a dirt track.
The piece of equipment being bolted on the spindles is a Sweet Ackerman Checker, of which there are only a few around. We have a feeling that after this story he'll have to sell them, or somebody else will. The spindle bars are just a way to measure the toe as the wheels are turned in both directions.
The process of checking the toe is to center the wheels, level both bars, and read the toe. Then the steering input shaft is turned 90 degrees, the bars leveled again, and the toe read again. What Sweet has found is that in most cases, a pavement race car will have good Ackerman as the wheels are turned to the left, but turning the wheels to the right will often show toe-in. So what? Well, Sweet has done testing and found in practically every lap a racer is running at the limit, the wheels are being turned both to the left and the right. So, when the wheels are turned to the right, usually because the rear end is sliding out from under the car a little, the toe-in actually makes the situation worse. The solution is usually up to the chassis builder, as this is chassis design problem, but Sweet says this all started when chassis builders went to "nonsymetrical" cars to get better weight distribution and roll-center gain. By changing the cars back to a "centered" design, where both the left and right side front suspension are the same lengths, this Ackerman problem would go away.
Late Model stock cars that use a rack-and-pinion steering system are usually equipped with a separate power servo (on the left) to add a power assist to the steering input. This small servo is installed between the driver and the rack on the steering input shaft, with hoses running to the power-steering pump system. Sweet says solidly mounting the servo to the chassis can actually shorten its life, so he recommends just installing it on the shaft. Note that the coupler is splined to slide on the shaft and the lock stud should be aligned to rest on the machined depression in the shaft. Sweet doesn't like welded-on U-joints and couplers and, as a solution, offers a complete line of splined shafts, U-joints, and couplers.
To install the firewall steering-shaft bearing, Victory Circle uses this 13/4-inch Mittler Brothers punch-and-flare tool that leaves a clean hole with a rolled lip for strength. Two 3/8-inch holes are drilled on each side of the large hole to mount the bearing.
This is what the steering shaft looks like completely assembled from the rack to the steering wheel. Getting the U-joints timed so that the steering input is even over the entire turning radius is critical. Sweet and VC both use a straightedge to align the U-joints to cancel out the nonlinear action of the U-joints. Sweet actually takes this to another level.