Making Alignment Bars for Your Race Car

Misalignment robs horsepower and horsepower costs money! Imagine the time and expense you would have to incur to get another 10 horsepower out of your engine. Then think about how many horsepower it would take to push your car all the way around the track, lap after lap, with a wheel that was out of alignment, scrubbing off little bits of rubber, generating heat and robbing speed as it goes down the straights. Getting the suspension trued up and the car rolling squarely down the track is the cheapest and easiest way to gain speed, and the very first place you should apply your energy. Once that is done, fine tuning to get the handling you want can pick up even more time in the turns. But a good set of alignment bars is key to making sure the car is square and making the best use of the engine's power. This is not the place to cut corners or do a shoddy job.

What you're trying to achieve...

The purpose of alignment bars is to provide a consistent, accurate mounting point for a set of strings that run the length of the car, parallel to the centerline an equal distance out on each side. The bars must be level with the ground plane when the car is level. From these strings you will measure in to points on the suspension to align the car. The material used and how they are mounted is not critical, and will vary from car to car, but they must be strong enough and mounted well enough that they can't be bumped out of position or bent when working on the car. The mounts must be accurate enough that the bars can be mounted in exactly the same position each time. We use 1" square steel tubing as it is readily available, strong and can be easily drilled and welded to make the mounting points and extensions you need.

Though string height and distance from the centerline is most critical, it can also be useful to make sure the bars are perpendicular to the car's centerline so that you can measure back from the bar to the axle centers. This will assure you that the axles are square with the car. Though only necessary to check this once, if you should damage a corner of the car, it will be a helpful reference point in putting on new suspension components at that corner and making sure the car is square.

Where to mount the bars...

Each car will offer a unique challenge, but most race cars have frame, engine or transmission components that can serve as a place to anchor your bars. Rear engined cars will have a transmission housing to which a plate can be bolted using existing transmission cover plate bolts. Rear wing mounting points can also be used. To this plate, the bar can be welded or bolted. Tube frame cars have frame members to which the bars can be bolted. If nothing easily lends itself as a flat spot to bolt to, you may have to devise a fitted plate or some extensions which are welded to the bar that reach to existing bolts which can be used. You can also weld on tabs or drill holes in non-critical frame components for the purpose or mounting the bars. On most race cars where bodywork can be removed there will be several ways for you to mount the bars.

We have provided below a couple of drawings of how we have mounted bars to our cars. You are by no means limited to these methods, and they may, in fact, be impossible on your particular car. They are simply provided as "idea starters".

Above: The front end of a Formula Ford here uses a square frame member as a clamping point. The alignment bar is clamped in place as shown or holes are drilled to bolt it in place.

Above: The rear bar on a Formula Ford can be bolted to a plate which is mounted to the rear of the gearbox using standoffs and existing bolt holes.

Above: The front end of a vintage IndyCar. Here the bars have extensions and tabs welded on to reach to a solid portion of the steering gear mount for an attachment location.

Above: At the rear of the IndyCar, pieces of tubing are welded on to reach a mount on the rear of the gearbox. A fitting that is part of the rear wing mount is also used for greater stability. You will use whatever strong and convenient points your particular car offers you.

On full bodied cars, mounting can be a little more difficult. Usually, however, there are frame components under the car to which bars can be mounted if bodywork cannot be removed. You may have to mount the bars fairly low under the car and use extensions to bring the strings up to wheel center height. If you use bumper mounting points which can be bumped during racing, check to make sure the bars are still true each time they are bolted on.

Leveling and squaring the bars...

After the bars are mounted, place the race car on the Sherline wheel plates and use the water leveling system to level the car. Then place a bubble level on the alignment bars to make sure they are also level. Measure out an equal distance from the car's centerline and scribe a line near each end of the front bar. From this point, measure to a point at the center of the roll bar or some other convenient spot on the center of the car to confirm that it is the same distance back on each side. This will mean the bar is square with the car. If the distance is not the same on both sides, shim the bar with spacers as required until the distance measures the same on both sides. Do the same for the rear bar. The bars should now be level and square with the car. Once the bars are square and level, mark, drill and weld your tabs or mounting points so that the bars can be attached this same way each time.

Mounting the reference strings...

Chances are the bars will not end up at the same height front and rear nor will they be at the height of the wheel centers. Measure the wheel center height to the ground and determine how long an extension you will need to weld on to the top or bottom of each bar to get a mounting hole to be at the wheel center height. (Being at exact wheel center height is not critical, but you should try and get as close as possible to make measuring toe in/out easy using the engraved extension "wings".) Make the extensions 1 inch longer than the determined distance and drill a hole for the string 1" in from the end of the extension. Weld on the extensions about 2 or 3 inches further out than the outer surface of the wheel plates so that you can measure back to the plates from this string. Make sure the hole centers are an equal distance out from each side of the car's centerline, both front and rear. This will assure that the string runs parallel to the car's centerline. By using holes in the bar to mount your strings rather than just tying them around the bar, you will be sure your strings are in exactly the same place each time.

In addition to the wheel center height string, we also mount extensions inboard of the wheel plates which represent the height of the bottom of the bodywork. This will give you ride height location even with the bodywork removed and the car up on the stands. By measuring from the bodywork height string down to the ground plane monofilament line which is stretched around the base of the system after leveling, you will always know your ride height. We provide paper rulers which may be cut out, folded and hung over the bodywork height string at the point they cross the ground plane string. This makes it easy to maintain a constant check on this dimension. (See figures 4, 5 and 6 in the instructions.) It is not critical that these lines be parallel with the centerline of the car, but they should be symmetrical on both sides of the car. In other words, they could be further apart at the rear than the front if the shape of the car makes that easier to work with. Height is the only critical factor on these lines.

Summary...

Doing a good job of designing and installing the alignment bars will make the job of aligning your car much easier. Total consistency is critical to being able to use your dimensions in comparison to previous dimensions in making meaningful adjustments to the car. This repeatability is the key to progressing toward better and better handling by going from known setting to new setting and noting the difference a change makes. It also allows you to return to a particular set of dimensions that worked well at a track the last time and start your racing weekend at your best known setting to fine tune from there. If the bars and strings are not mounted exactly the same each time, the comparative dimensions are meaningless, regardless of how expensive an alignment system you use. With the Sherline system and good alignment bars you will find that there is no need for fancy lasers or delicate mirror/optical systems. You will be able to determine dimensions time after time as accurately as you can measure with your ruler, because the points from which and to which you are measuring are consistent and easy to see.

Proper use of this system in determining dimensions will put you on an equal footing with teams using equipment costing many times more. How wisely you use that information will determine who gets to take the victory lap.

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