• Alignment 101


    I did alignments for about 8 years back in the '80s. As you can see, most of my knowledge is "old school", but I understand the concepts well. In addition, I did "regular" cars mostly. Sure, I did lots of Porsches, Corvettes, and all other cars...but they were mainly stock. I didn't do a lot of work with lowered cars, raised trucks, and adjustable suspensions, etc. Now that I've given the background, here we go.

    In setting alignments, there are 3 main angles: Caster, Camber, and Toe. I'll present them in the order in which they should be set (because some of them affect others...so for example if you set toe, then adjust caster, you've just messed up your toe).

    Caster is the most difficult angle to visualize. It's the angle between the upper and lower ball joints as viewed from the SIDE of the car. If you don't have an upper ball joint (re: struts), then it's the upper strut mount. If the upper ball joint is directly above the lower, the caster is zero. As you move the upper ball joint back, you are INCREASING caster.

    Caster typically is positive (the only car I've ever worked in with negative caster is the old Dodge Dart) and typically runs around 1-5 degrees. There are trade-offs when setting caster. The higher it's set, the more stable the car feels in terms of "tracking". Think of it as being able to take your hands off the steering wheel and the car continues to go straight. In addition, higher caster gives SLIGHTLY improved ride quality because the road forces are not transmitted strictly vertically...so the chassis absorbs more. The downside of high caster is mainly more difficult steering effort. With today's power steering, this is typically not an issue...but in the old days it was one reason for low caster specs.

    Caster does not DIRECTLY cause tire wear (more on that later). However, the important thing about caster is that it is set to about the same value on each side of the car. The reason for this is that a caster DIFFERENCE from side to side will result in the car pulling to one side. Some techs prefer to add 1/4 to 1/2 degree to the right side of a car to compensate for road crown (the way roads are built with a slight slope to allow for water drainage). I didn't do this because invariably the first thing a customer would do upon getting an alignment was take the car to a flat location and "test" for the pull. When I did alignments on my OWN car, I did set the left side lower and I'd set the caster as high as reasonably possible to improve stability.

    When I said caster doesn't DIRECTLY cause tire wear, here is what I mean. Let's assume you put the left caster at 2 degrees and the right at 4 degrees. The car will pull to the left. Now let's assume you go to a large parking lot, start driving and let go of the steering wheel, and just maintain a speed of 30 mph. The car will go in a circle. It may be a large circle, but it will be a circle. The tires will not wear irregularly due to this. However, in real life what would happen with this same car is that you'd be driving down the road, and the car would want to pull to the left. Your obvious reaction would be to turn the steering wheel slightly to the right to correct for this. As a result of doing this, you are "creating" toe IN on the left front tire and toe OUT on the right front. THIS will cause tire wear on both front tires as you'll see in my discussion later about toe.

    Next post I'll discuss Camber.



    Camber is the angle of the tire as viewed from the FRONT of the car. If the top of the tire is tilted out, the camber is positive. I'm a bit rusty on this next parts, so trout can help me. My memory is that most rear wheel drive cars had slight positive camber (perhaps 1/4 to 3/4 degrees). This initial "dial in" is for two reasons. One is because as you accelerate in a car, the front end lifts slightly, and therefore you are "running" at zero camber...which is best for tire wear. The second reason is that cars are aligned without occupants, and when a person sits in the car, the camber will change slightly.

    If you want a car to handle better, you'd want to dial in some negative camber. This would bias the tire on the outer edge of the turn such that it is closer to "straight up" when cornering. How much to dial in? I don't know....as I mentioned early on...setting up cars for racing and so on was not my focus. Of course on an oval track where you are turning the same way all the time, you'd likely want different settings on the left and you would on the right... would know about this along with "stagger" and other racing techniques.

    Incorrect camber WILL wear tires, but in my opinion it is a MUCH smaller component of tire wear than toe. My estimate is that camber is responsible for 10-20% of tire wear...with the remainder being toe. (or hard starts if you have a GT500) . Camber wear appears as a GRADUAL uneven wear across one half or more of the tire. If you see an edge worn off...this is NOT camber wear...you'd need 10 degrees of camber to do that...and cars don't have enough adjustment to dial in 10 degrees.

    The method to adjust camber varies considerably by vehicle. Again, remember, my experience is from the '80s. Rear wheel drive cars with "parallelogram" suspensions (upper and lower control arms) used some method of moving the upper control arm. For example, GM MOSTLY used shims between the control arm and the frame. Chrysler used slotted holes in the frame where the upper control arms were bolted on. Ford used eccentric cams you could rotate. Now it gets a bit difficult to describe here, but ON THE TYPES OF CARS MENTIONED ABOVE, the camber and caster are adjusted simultaneously. How? Well, you first determine with your machine what you need. Let's say you need to increase caster 2 degrees on the left side, and increase camber by 1/2 degree. In that case, you want to move the ENTIRE upper left control arm OUT, but move the FRONT of the control arm out MORE than the rear. Moving the control arm out gives you the camber...but moving the front out relative to the rear gives you the caster you need. (I need a model like that rubber knee joint that the orthopaedic doctor uses)

    Then along came front wheel drive cars...and things changed. These cars don't have the ability to EASILY move the control arm to get caster. However, the good news is that manufacturing/design had improved to the point where they could keep caster within limits at the factory so that it did not need adjustment. Therefore, on MANY front drive cars, caster is not NORMALLY adjustable, nor is it necessary to adjust. If you absolutely MUST adjust it due to a wreck or some other reason, the aftermarket steps in and designed a variety of things to allow the adjustment of caster. Most of these require you to drop the strut by removing the upper nuts, then elongating the holes front to back so that the entire strut can be tilted slightly. The caster/camber plates for the SN197 work this way. Below is a pic. Note that moving all three bolts to the "other" set of holes would provide more camber by a set amount, and then sliding all three in the slotted holes will give you the caster you need. I'm not sure, but I believe these would require grinding the existing slots to match...ouch.


    I cannot stress enough how many different varieties of adjustment there are for all the different cars. Eccentric cams (Chevy Citation), plastic shims (FWD Dodge Omni to adjust REAR camber and toe), elongated holes (rear wheel drive Chryslers), offset ball joints (Chevette), offset adjustable bushings that go in the steering knuckle (some trucks...GM I think), and threaded lower rods ('80s Mustangs).

    Here are some pics:
    A strut car (Merkur): Note the eccentric cam...rotating this moves the lower control arm in or out, adjusting Camber.

    Attachment 6928

    A diagram illustrating camber, caster, and toe:
    Attachment 6929

    Here's the kind of stuff I worked on...this was a GM setup such as F-body (Camaros) and A-body (Chevelles,Skylark, etc.). Loosen the nuts, insert or remove shims to adjust angles, then retighten and measure.

    Attachment 6930

    A race setup where it's easy to see the simple method used.
    Attachment 6931

    Here is the eccentric cam on the strut...a la Chevy Citation and many others (Pontiac Fiero also).

    Next up....


    Toe is the easiest angle to explain.

    Toe is the angle of the tires as viewed from ABOVE the car. Stand up, look down at your feet, and point them straight ahead. That would be zero toe. Now point both toes in...that's called toe-in, and vice versa. Toe is the last angle of the three to set. It doesn't affect handling significantly...only if it's WAY off. However, it is the most critical angle to prevent tire wear. Toe wear is easy to see when it's really severe...it's a combination of "sawtoothing" on the "exposed" edge of the tire and severe wear on that edge. HOwever, it's difficult to detect early in it's life. Over the years, I learned to feel it rather than see it. While sitting on a stool directly beside your tire, take your hand and lay it on the edge so that your fingers lay across the outer could inches of the tire. Slowly run your hand one direction and feel for "lumpiness" or jagged edges. Now run your hand the other direction and do the same thing. If one direction feels significantly different, you're probably feeling the sawtoothing associated with toe. You must do this on both the outer edge of the tire and the inner edge. If the INNER edge has this feeling, the car has too much toe OUT (or it's possible that it has less toe IN than is needed). If the OUTER edge has this, the car has too much toe IN.

    To explain this wear, try this. Take a loose tire sitting in your garage and turn it severely IN. THen imagine the car going down the road STRAIGHT. Obviously the tire is being "scrubbed" into the pavement, thus causing the sawtoothing. I've included some pics below, but I couldn't find one that I thought truly shows the wear I used to see every day. The sawtoothing typically occurs only on the edge...NOT across the whole tire like the photos show.

    To adjust toe, you adjust the tie rods on the front suspension. If you have a parallelogram system (old cars...before rack and pinion), you loosen the clamps on the tie rod sleeve, then use a special claw wrench (see the pic below...don't use a vice grips like the picture shows....you'll likely damage the sleeve). One tie rod has a regular thread, the other has a left-handed thread. When you rotate the sleeve, it either pulls both tie rods in, or pushes both out...thus adjusting the toe.

    Now you might wonder...which side do I adjust? Well, that's how you center the steering wheel. On an alignment machine, you have a tool that holds the steering wheel centered while you check the angle, and the machine tells you which side to adjust. If you're doing this at home, you'll have to use a trial and error approach. If you turn both tie rods an equal amount, the same direction, then the toe will not change, but the location of the steering wheel will.

    As a practical matter, those sleeves are famous for rusting. Spray some penetrating lube in the slot before attempting to turn them...then be patient.

    If you have a rack and pinion car, then the procedure is slightly different. Instead of a sleeve, there is a jam nut on the inner tie rod end. Loosen this nut, then use a pipe wrench to turn the rod...and retighten the nut. Since the inner end of the inner tie rod is inside the "accordion boot" of the rack and pinion, you can't see it...but it's a ball and socket, so it will turn freely.

    Toe must be set precisely. If it's off by 1/8", you'll get some wear. If it's off 1/4", you'll get LOTS of wear. And if it's off further...well....you'll probably notice the car doesn't drive well. This is why I think it's difficult to do a good alignment in your garage....being off even slightly can cause problems. Using a tape measurer allows too much room for error. If you're going to do it in your garage...at least you need a long stick with markings....that would work pretty well. In that case you measure the distance between the INNER edge of the BACK side of the front tires (I know, that's confusing), and then subtract it from measuring the INNER edge of the FRONT side of the front tires. If this number is positive, your car is toed OUT.

    Typically rear wheel drive cars use a slight amount of toe IN, because as you accelerate and drive, the front of the car lifts slightly and the tires dynamically move out. Front drive cars typically use a slight amount of toe OUT because the driving forces of the front axles cause the toe to pull IN as you drive. When I say slight...typical values for toe are about 1/8" or so.

    Next....toe out on turns...technically not an adjustable angle...but we'll discuss it briefly.

    Any questions?


    This is a common tool for adjusting toe on older suspensions. The little "hook" on the end fits into a groove on the tie rod sleeve and is used to rotate the sleeve. The sleeve has left handed threads on one end, and right handed on the other, so rotating the sleeve either moves both tie rods in, or both out...thus adjusting toe.
    I would imagine very few cars today need this tool...as rack n pinions don't have this.

    In real life you'll never see a tire worn as dramatically as the first pic, but the picture is exaggerated to show what toe wear would look like. It gives a feathered appearance where one side of the tread is pointy and the other is not.

    The second pic is a more typical "real world" example of toe wear. Toe IN will cause the tire to wear like this on the outer edge, and too much toe OUT will cause it to wear on the inner edge.
    http://i189.photobucket.com/albums/z...sUnited/a4.jpg http://i189.photobucket.com/albums/z...sUnited/a5.jpg

    These next two show adjusting toe via the tie rod sleeve I mentioned above. First you must loosen two clamps on the sleeve. Then you use the tool above to rotate the sleeve. They show below the guy using vice grips...bad idea...as you'll crush the clamp, plus they are usually so rusty/tight that vice grips won't work.http://i189.photobucket.com/albums/z...sUnited/a3.jpg

    Lastly a simple schematic of toe http://i189.photobucket.com/albums/z...sUnited/a1.jpg

    Click on the Extras link at the top, and then you must download a program and run it. It's free, and called the Nitto alignment demo.
    Nitto Tire - High Performance Tires for Car and Truck Enthusiasts

    This article was originally published in forum thread: Alignment started by Alloy Dave View original post