Not too many of us have an unlimited racing budget. When deciding where to spend our racing dollars the choice is sometimes between power and handling. My first choice is always handling, as the only thing worse than a gutless, ill handling race car is a POWERFUL, ill handling race car! The handling components of a car include the alignment of the suspension as well as the choice of shocks and tires. Although we will be discussing alignment here, keep in mind that having a perfectly aligned car is a good place to start, but a set of bad tires can undo all your best efforts. This requirement for harmony between so many diverse components is what got me thinking about how alignment is often measured as opposed to how it should be measured.
I probably look at a race car a little differently than most drivers because of my background. I own a machine shop that has produced millions of parts in the last twenty-five years. The parts I manufacture must pass inspection by customers thousands of miles away who may measure the parts with different methods and tools than I use. In some cases thousands of dollars worth of parts can be scrapped over the method used to determine a dimension. As you can see, accurate, repeatable measurements are an important part of my business.
The first time I had someone help me align my race car I was shocked by the methods they used to determine the settings. We couldn't seem to get the same readings twice in a row, much less have a third party inspect the car and get the same figures. I was then told that to get better results I would have to buy thousands of dollars worth of alignment gear. From my machine shop experience I already knew that good measurements require good tools, so this made some sense. I also knew that for consistency you needed an integrated system that would allow you to measure these different points in unison, not individually. It also seemed obvious that any system that didn't start with a perfectly level car wasn't going to yield any usable results. But when I looked at what was on the market, I could only find a lot of single-use tools that addressed each particular problem individually.
I began to look at the problem like an aircraft company inspector who was looking for the right way to measure not just a wing or an aileron, but the entire airplane. I felt I needed an integrated system that would give me a meaningful set of figures, so I started from scratch and came up with my own system. In doing so I feel I've become qualified to pass on to you how to make good, meaningful measurements; however, I make no claim to know what those measurements should be for your particular car. That part was and always will be up to you. Also, my experience has been in working with race cars and not production cars where the adjustments you can make are more limited. The methods I have applied here are meant to show you how to think about obtaining measurements as well as how to obtain them. If you have some shop skills, you should be able to use these techniques and the tools you already have to come up with a system of your own that will achieve equally accurate and usable results.
What's in a System...
Any alignment system consists of two parts: Fixed reference points from which you measure and adjustable reference points on the suspension to which you measure and then adjust. For the purposes of this article, we will use a Formula Ford and SHERLINE's "Inspection Grade" Alignment System, but no matter how you accomplish the tasks we are demonstrating, the results can help you improve your car's handling. Of course, accuracy is important so the system you use must be precise and firmly mounted. The car must also be level or the measurements are meaningless. Therefore, the order to proceed is: 1) Level the car, 2) Apply fixed alignment bars and strings for reference, 3) Make and record accurate dimensions and 4) Adjust to specs.
Usually, dimensions are taken from an alignment string running parallel to the car's centerline to points on the car's wheel rims. Wheels and tires are not very consistent or accurate, so I have replaced the wheels with aluminum tooling plate alignment plates that are not only flat and consistent, they also incorporate several other features that will make alignment easier. One important feature is a hydraulic scale at each plate which reads out corner weights at all times. As adjustments are made, you can always see how it effects the corner weights without having to take separate weight readings.
Leveling the Car...
It should be obvious that for camber angles, wheel weights, wing heights, etc. to have meaning, the car must be sitting as level as possible. Even concrete shop floors are often not level, and finding a level spot in the pits is nearly impossible. Therefore, a way to level the car must be provided. Our system takes advantage of the simple principle that water seeks its own level. On the bottom of each wheel plate is a sight glass and level mark. Interconnecting all four wheel plates with PVC pipe and tubing filled with water allows you to read the water level at each wheel. A hex head bolt "jack screw" provides height adjustment to bring each wheel plate to the same level. Once leveled, mark each wheel position on the ground with paint (in your shop) or chalk (in the pits). That way, you can set up quickly in the same spot without having to re-level.
Alignment Bars...
Misalignment robs horsepower and horsepower costs money! Imagine the time and expense you would have to incur to squeeze 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. A good set of alignment bars is absolutely key to truing up your suspension. This is the last place you want to cut corners and the first place to apply your time and money to get more speed out of your car.
Since each car is different, you or your fabrication shop will have to determine the best way to mount bars on your car. What you are trying to do is mount a set of bars front and rear perpendicular to the car's centerline and level with the ground. Measure out an equal distance to each side a few inches outside the wheels and run a string from front to rear on each side. This is your reference line for all measurements to the suspension. It should be at about wheel center height. We run an additional string closer in which represents the height of the bottom of the car for ride height measurements.
NOTE: For more information on making alignment bars, click here.
The bars must bolt or clamp on firmly and be able to be mounted exactly the same each time. They should be level when the car is level. (If the car starts out level, it's really easy to see if the frame has twisted by looking at the bars when you bolt them on after a practice session or race.) We use 1" square steel tubing with extensions welded on to get the strings at the right heights. If you can't make these yourself, most fabrication shops have done this job many times and will be able to come up with a good set for your car once you describe what you want.
You will also need to find a way to lock your front wheels in the straight ahead position. It should be a mark or pin that is very positive and consistent so it is always in the same position for measurement.
Suspension Plates...
Replacing the wheels with accurate plates offers several advantages. It provides much more accurate points to measure to. It also provides a place to attach a leveling system and weight scale. We have provided a relatively frictionless ball bearing roller system that allows the suspension to move in and out during adjustment without having to roll the car back and forth to "reset" the suspension. (The rollers can be locked when you don't want the car to move.) Another benefit of the plates is that it makes it a lot easier to move around the car and make suspension adjustments without the tires in your way.
Add Ballast...
To accurately simulate real conditions, it is best if the car is as close to racing weight as possible. The fuel tank should be full or at a known level that you always use when taking measurements. Use sandbags in the driver's seat to simulate the driver's weight and position as closely as possible. (No jokes about the sandbags also duplicating the driver's IQ or driving skill...)
The car should now be level, properly weighted, have alignment bars and wheel plates in place and is ready for measurement. The first item on the agenda is to see where we are.
Keeping Track of Data...
A race car suspension is a complicated piece of geometry with a seemingly infinite number of variables. The more adjustments you have, the further it is possible to get from the ideal setup. You're left with a car that handles anywhere from just plain "no fun to drive" to "flat out dangerous". The best way to get from unknown to known is with a good map, and an alignment system plus good recordkeeping will show you where you are and where you've been. Once you have that information it's a lot easier to get where you are trying to go. When starting on a car you've never measured before or when reassembling a suspension from scratch, the centerline of the car and the alignment bars are your only "knowns". I'd suggest if you're starting with an assembled car and you know how it handles, before you change any settings, use your alignment system to carefully measure and record all the existing settings. It may be way off as far as the numbers go, but if you make them all "perfect" and the car handles worse, you can at least go back to where you were before. There may have been a lot of experimentation that went into that particular setup, and sometimes a lot of "wrongs" add up to a "right".
We have generated a set of data sheets which we provide with the SHERLINE system to help keep track of all the important settings for your car. (Call or write and we'll send you a free copy.) You can make up your own form with blanks for the data that is pertinent to your car. Have copies made, keep them on a clipboard or in a 3-ring notebook and fill one out each time you set up the car. Keeping them in chronological order will give you a good roadmap from where you started to where you are now. It is common practice in all big racing teams to record all suspension settings after each session or race. That data along with notes on how the car was handling will be valuable later. It's worth your time to do the same thing. You will find each track you race at has a slightly different set of preferred settings. Good records will let you preset the car to these specs in your shop so next time at that track you roll off the trailer for the first practice session with a good handling car. The longer you keep this up, the more "dialed-in" your car will be.
It is worth noting that as you move toward a good setup, only make one change at a time. It is often tempting to change two or three things to save time, but as in any scientific experiment, controlling the variables makes the data much easier to interpret. One change, even if it makes the car worse, gives you more positive information than several changes. You might make 3 changes and the car gets better, but 2 of the changes might be offsetting part of the improvement provided by the third. It may take a little patience, but in the end you will probably get to the result you want quicker because your route was more direct when you learned something usable from every single adjustment.
The Adjustments...
Suspension adjustments are all interrelated, and a change in one affects the others. The adjustments you make are never isolated, and what you are actually working for is a sequence that spirals in on the perfect setting. The first adjustments may be fairly major, and their effect on other settings will be large. As you work your way around the car several times, the changes will get less and less until you finally achieve a balance. Although I have seen it attempted many times, you simply cannot adjust one component such as corner weights or ride height and not check to see what it has done to other settings. I've seen crew members adjusting corner weights with the front wheels not pointed straight ahead. Turning the wheels straight will completely throw off their settings. I've seen a car being adjusted on an expensive drive-on alignment rack when you could stand across the pits and see the rack was twisted and not level. The figures they were getting will be worthless. Keep this in mind as you adjust and work toward a setting, don't expect to achieve in with one adjustment.
When rebuilding the car after major work, several adjustments are made as the suspension is reassembled. This is the point where you are establishing that the wheels are the right distance out from the centerline of the car (track width) and that they are the proper distance apart (wheelbase) and from the nose or tail. Once those basic dimensions are established and the caster angle is set to the designer's specs, you probably won't do much adjusting in those areas. If you are starting to set up a new car or one that you have never aligned before and aren't sure any of those dimensions are correct, check them all and get them right before you move on to start setting the other adjustments.
NOTE: When making suspension adjustments I suggest that you never leave a loose bolt or nut. Either tighten each one as you go or remove it completely. This may require more loosening and tightening, but you often can't tell by looking if a nut is tight. This way you will never put the car back on the track with a suspension component that has not been fully secured.
Caster...
Caster is the angle the kingpin is adjusted off vertical front to back. The purpose of caster is help the car track in a straight line if you let go of the steering wheel. Race cars run less caster angle than production cars both because tracking is less critical in a race car and because excess caster can cause a car to "push" in tight turns as it puts the tires more "on edge".
I have had a number of people show me methods of checking caster by turning the wheels approximately 20° and measuring difference in angle, however, I am not convinced this method is accurate in all cases. I prefer to measure it at the pivot points when the car is level. A simple gauge may be needed to accomplish this. A formula car is usually set to 3° or less.
Camber...
Again, you will need to know the specs on your car for the proper setting and start there. Simply placing an electronic angle gauge on the wheel plate will give you a direct reading of where you are set. To maximize tire wear, most street cars are set pretty close to zero. A small amount of negative camber (the bottoms of the front or rear wheels farther apart than the top) is often dialed into race cars because it increases "bite" in the turns. Racing speed cornering forces can cause the suspension and tires to roll under causing uneven contact on the tire patch. By setting a negative camber angle in the suspension you are trying to put the maximum amount of tire patch in contact with the road on the outside tires during hard cornering. You will know you have a successful setting when you measure your tire temperatures after a session and they show the same temperature at the outside, middle and inside of the tread. If you can't measure tire temperatures, watch for clues in your tire wear pattern. If they're wearing out at the outside, try more negative camber. Because sidewall stiffness varies in different tires, a new set may perform better with a different camber setting.
Toe In/Out...
Toeing the front wheels in slightly adds stability to the steering. Toe out is more unstable and could cause twitchy handling. Extreme toe in or out will cause scrubbing and drag. The most important thing you are checking at first is to see that the settings are the same on both sides, then fine tune to your car's specs.
On each wheel plate we have added pieces of 1" angle that stick out front and rear. These are laser engraved with calibrations that make reference measurements easier. Since most people are used to taking measurements at the wheel rims, we have marked the extensions with scales at each of the wheel rim diameters. Using the scale for your car's wheel diameter, measure from the alignment bar string in to the zero point on the rear extension.* Note the dimension where it crosses the string. Then move the ruler to the corresponding scale on the front extension and place the same ruler dimension on the string. Where the end of the ruler falls on the front extension scale will be the amount of offset between rear and front. As an alternative, we have calculated the angular equivalents and marked them on the ends of the extensions. You can measure the rear distance at the end of the extension, transfer it to the end of the front extension and read out the Toe In angle directly in degrees. (If your ruler goes past the zero position on the front scale your suspension is Toed Out. Reverse your procedure by measuring the front first and then the rear to find out how far.)
*Note: If you are not using a plate system, you will be measuring instead to the rim of the wheel.
Ackermann Geometry...
Because the radius of a turn is shorter for the inside wheel, suspension geometry is designed to account for this by having the outside wheel turn slightly less than the inside wheel. On passenger cars where cornering forces are low and reducing drag (maximizing tire wear) is a major factor, the geometry is fairly straightforward. On a race car, however, the outside tire is heavily loaded in a turn which causes the tire to twist so that the patch of tire touching the ground might be pointing slightly less into the turn than the angle of the wheel. This is the "skid angle" and should be accounted for in the design of the geometry for your car.
To measure the settings on your car, turn the steering wheel all the way to one side and measure the distance of the front of the rim from the string on both sides of the car. Subtract the "outside" wheel's dimension from the "inside" wheel's dimension to find out the difference. Because it is based on the geometry designed into the car, there probably isn't much you can do to adjust Ackermann distances, but it is worth checking and recording the dimensions to confirm that they are up to spec and equal on both sides.
Bump Steer...
When a wheel travels through the arc allowed by its suspension, differences in the lengths of the suspension arms may cause it to twist as it moves up or down. This has the effect of "steering" the car slightly in bumps, making it feel "twitchy. If both wheels move the same amount on a straightaway, the effect cancels itself out and isn't noticed, but in a turn or when only one wheel hits a bump, the car can take a little step to the side which can be unsettling to the driver's nerves. Remember also that bump steer is not just a phenomenon of the front wheels, but happens at the rear wheels as well. Depending on the design of your car's suspension, you may be limited in how much you can do about it beyond measuring what your car actually has and making sure it is the same on both sides. Considered a fact of life in suspension design, many attempts have been made to reduce it, eliminate it and even to use it to the car's advantage. Whether or not you consider the designer of your car successful in his attempts depends on your handling preferences and driving style. Most just learn to compensate as needed with steering movements to offset the effect.
To measure bump steer, support the end of the car you are measuring with a jack and release the springs and shocks so the suspension moves freely. With the steering wheel locked in the centered position, measure the front and rear wheel rim offset (just like measuring for toe) at the extreme up and down positions of the suspension and compare them to the dimensions you got for the normal resting position. Any differences you note will have a steering effect on the car as the suspension moves. Once you have assured it is the same on both sides, the design of your particular suspension will determine what, if anything, can be done about it.
Ride Height...
Now we're down to the easy ones. Since we already have a string that represents the bottom of the car and another one that represents the ground plane, a simple measurement where they cross will give you ride height. We print up some paper rulers that can be cut out and hung over the upper line so you can just walk around and check all four corners at any time. (The rulers must be very light so they don't pull down on the strings.) Changes to ride height will affect other dimensions. Recheck all dimensions after you make your last adjustment.
Wing Heights/Angles...
These can be done with the car on the ground, but your most accurate measurements will be made while the car is still leveled and the ground plane lines are in place. For rear wings where the dimension is a little longer, a weight or "plumb bob" on a string can help make sure you are measuring straight down each time.
Corner Weights...
We have provided a hydraulic scale on each wheel plate to constantly read out the force the suspension is putting to the ground through that wheel. Remember that because there is caster in the front wheels, the steering must be locked straight ahead for the weight figures to be meaningful. Turning the front wheels will change the weight readings. As you make other adjustments, you can always see what they are doing to the balance of the car. Just remember that when you make adjustments to the springs to change these "weights", you are not actually moving any weight around, only transferring forces. Naturally you want to get the forces balanced as well as you can, but if the car has too much weight on one side, changing the spring settings may help a little, but the weight hasn't actually changed positions. Think about your car as a board with warped down corners. On a flat surface, two opposite diagonal corners will be sharing most of the weight, one other corner will have a little weight on it and the fourth corner will be in the air. You can warp the board differently to change which corners hold up the weight, and if you get it perfect, all four corners will touch equally, but no weight in the board has actually moved. If it was too heavy on the one side, it's still too heavy on that side. You can't rewrite the laws of physics to transfer weight from one side of the car to the other simply by adjusting the springs. I often think a lot of emphasis has been placed on corner weights simply because they are easy to measure and there are a lot of systems out there to do it. Having all the corner weights equal if the car isn't properly balanced and aligned won't mean much to your lap times.
Don't get carried away with the importance of any individual setting...
Because you learn to measure a particular aspect of your car's suspension, there is sometimes a tendency to worry too much about getting it "perfect". Wheel weights can be overly important to a person with a new set of scales. Others learn what bump steer is and then get caught up in thinking that "if I just get the bump steer adjusted perfectly it will solve all my car's handling problems." Don't let any single aspect of suspension tuning distract from your overall concern with the interrelated nature of the whole car.
Engineering is a compromise, and there are few gains to be made without a corresponding sacrifice somewhere else. You are searching for the ultimate "balance" of settings, not necessarily perfection in every single setting. If you have a car that is already drivable, look at your changes the way a good chef uses spices: Just the right amount of each spice makes the dish delicious, while too much of any one can ruin the whole thing.
Patience and good measurements pay off...
Whether you race to win or race for fun, a good handling car is critical to the successful achievement of your racing goals. If you've been trying to "eyeball" suspension settings or have been using crude, inaccurate tools or invalid methods, I hope this article has shown that it doesn't take a lot of time or a big budget to get good, usable dimensions. With a few simple fixtures and tools you can get meaningful information off your suspension system. A history of these dimensions compared to a record of the car's performance at each setting will eventually lead you closer and closer to that "perfect setup". With some designs and older cars, "good handling" may be a relative term, but at least you'll know you are enjoying the best your car has to offer and it is handling as good or better than it ever has for any of its past drivers.
Acknowledgments...
I would like to thank Craig Libuse for his excellent drawings and for his patience in fine tuning my scribblings. I would also like to thank Jerry Eissert for his help in passing on information on all phases of race car preparation gathered over 50 years of racing and winning.
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