What tires should I use?

I've been a suspension and alignment specialist since the mid '80s, and I taught it for nine years, and I never heard of "front wheel displacement". If I had to guess, I'd suspect that has to do with how much a front wheel is forward or rearward compared to the other front wheel, but that would only be a secondary angle used to assess a crash repair. It's not an angle you'd try to or be able to adjust. I looked in the service manual and found the same listing, but no explanation of what it is.

As for the video, you might want to do a search for "Red Green tv show", (one of my favorites). This reminds me of a coworker who used a carpenter's level to set the camber on an old '74 Impala, and then a tape measure to set total toe. With the alignment equipment we had back then, getting camber within plus or minus a quarter degree was more than sufficient, and total toe was less critical than it is today. He managed to make his car go straight, with a straight steering wheel and no unusual tire wear. That's the goal of all alignments, but since the mid '80s, especially with light-weight front-wheel-drive cars, those older mechanical alignment machines just aren't precise enough, but they were more precise than what you're trying to do.

I'm sorry that I'm not familiar with how your specs are shown. I believe that's in minutes and seconds. I always set up my alignment computers to read in degrees. (For reference, 0.00 degrees means the wheel is standing perfectly straight up, and 90.00 degrees would mean the wheel is laying on its side). Most cars and trucks call for slightly positive camber, between roughly 0.10 to 0.70 degrees. That's tipped out on top. Your car calls for negative camber; the wheels are tipped in on top. That is done for better high-speed cornering at the expense of even tire wear. That is also a compromise for the goal of placing the car's weight directly of the center of the wheel bearing.

Most mechanics set their computers up to read one place after the decimal point because it is faster. I set mine up to read two places for more accuracy. With minutes and seconds, you have no choice but to get the better accuracy

In the early '90s, the majority of Chrysler products I worked on called for 0.30 degrees camber on the front, and I learned from numerous test-drives they needed to have 0.06 degrees more camber on the left to make up for road crown. With those settings, I knew no one would come back with a complaint of pulling to either side. If I had my computer set up to read only one decimal place, 0.34 degrees would be rounded off to show 0.3, and 0.36 degrees would show up as 0.4 degrees. The computer would say I had 0.1 degree more camber on the left, which is too much, but in reality, I'd have 0.02 degrees, which is not enough. Reading to the hundredth of a degree is that important on cars as long ago as the early '90s. With the old machines, the best we could do was to read to the eighth of a degree, if your eyes were that good. We've gone from reading to 1/8th degree to needing to read to 0.01 degree. You can't do that with a level.

To address your procedure, first be aware very few cars have the same distance between the two rear wheels as the two front wheels. That can be seen in the video. The level is only an inch out from the edge of the rear wheel, so why is the beam hitting the ruler at over six inches out? That rear wheel would have to be seriously toed-out to the point of scrubbing the tread off in a few hundred miles.

You can see that with your independent rear suspension, camber and toe are adjustable, but how do you know where you're starting from? If the rear wheel is toed-out, it's going to show you need to turn the front wheel toed-out too, then they'd both be off. Years ago, when we first started doing four-wheel alignments, we had to drive the vehicles onto the hoist backward, adjust camber, then adjust individual toe on one wheel until total toe was right. It was understood there was no real precision on getting both wheels parallel to the center-line of the car. Then we had to do calculations to figure out where to set the front wheels. Drive off the hoist, then back onto it forward to set the front wheels. Toe had to be calculated from specs plus what we had in the back. That was done to insure the steering wheel would be straight.

Today the alignment computer looks at the direction the rear wheels are steering, and uses that to show us where to set front toe to make total toe correct for best tire wear, and the two individual toes to insure a straight steering wheel. Even on vehicles with solid rear axles, it is very common for the rear wheels to be steering off to one side a little, (that's called "thrust angle"). The computer tells us to adjust the two front wheels to steer off-center the same way so they're parallel to the rear wheels. We can't see that by eye, but that is what gives us the straight steering wheel. Imagine you have all four wheels perfectly parallel and precisely in the corners of a big rectangle. Now lift the body up off the axles, rotate it slightly, and set it back down. The body is going slightly sideways down the road, but the steering wheel is straight. The alignment computer takes care of that for us. Your method does not. Even if you were to get lucky and get total toe close but the steering wheel is off center, you'd need to readjust each tie rod link to turn each front wheel to match the steering wheel. Some of those final fine tuning adjustments can be as little a 1/16 of a turn on the adjuster. You can't see that by eye.

The alignment computer also takes into account a rear axle that is moved straight to the left or right a little. All four wheels can still be perfectly parallel, and the steering wheel will be straight, but with the laser line, you'll be turning the front wheels to try to compensate for that offset that shouldn't be compensated for.

I don't have a clue what they're asking us to do for measuring caster, but there is no physical way to do that with a level. Alignment computers have us turn the front wheels to the left a specified amount, then it takes camber readings for both front wheels. Next we turn the same amount to the right, then it takes two more camber readings. From those, it calculates caster. This is because camber changes as the wheels turn left and right, and the amount of change is related to the caster setting.

Camber, (the tilt in or out on top of the wheel), has the most effect on pulling. A tire wants to pull in the direction it's leaning. Camber has to be in specs for good tire wear, and it must be nearly equal to avoid a pull to one side. Caster also affects pulling, but it has half the effect as camber. To say that another way, if you had 0.25 degrees camber pull to the left, that could be offset with a 0.50 degree caster pull to the right. The good news is caster has almost no affect on pulling on 99 percent of front-wheel-drive cars, so while there is always a spec given, there is rarely a means of adjusting it, as it isn't needed.

Caster is what causes a wheel to lean into a turn, and it is what causes the steering system to want to return to center after you go around a corner. Higher caster is responsible for reducing steering wander. Lower caster makes really old heavy trucks without power steering easy to steer.

The next problem is cars on the alignment hoist are always sitting on turntables that are free to slide left and right. Those let the tires squirt out to an orientation different than what they do as you're driving down the road. That is the condition all cars are expected to be in for the specs to apply. You're working on a truck with tires stuck to the ground and unable to slide out. If your truck was in perfect alignment, then you drove it onto the alignment hoist after removing those slip plates, (turn tables), you'd find all of the readings would be nowhere close to specs. You're trying to make adjustments with specs that don't apply to the way the truck is sitting.

The only time this method has any value is after rebuilding the entire suspension system and you want to get camber and toe good enough to drive to the alignment shop without chewing up the tires. If you only replaced one part, that is the only wheel that might not be in specs. If your laser shows the other three wheels are off, what caused them to change? They had good tire wear patterns, but now you want to change some adjustment. You're going to end up with the misery of an off-center steering wheel, tire wear, and a pull. I do all my own repairs, but this is one time to bite the bullet and take it to an alignment shop.

Loading is not something the alignment computer requires unless specified. The only other car I've ever seen this on was the early Dodge Neons, but that was special circumstances. There is a class of racing that requires the alignment to be set to "factory specs". Chrysler added "loaded" specs to the service manual to make their cars legal and competitive for that class. I never learned that at any of the Chrysler classes I attended. I performed an alignment on one with the driver in the seat the whole time, and to the settings he showed me in the service manual.

I can't argue with your service manual, but in my opinion, you're looking at this backward. The caster, camber, and toe readings on the alignment computer are not what you have while driving down the road. Those specs take into account that at a minimum, there is going to be a driver in the car while driving, but not during the alignment. The alignment takes takes into account the expected weight. You're asking to have weight added to affect the alignment.

To say that a different way, if those specs can only be right with 350 pounds added to the car, the alignment can only be right when driving down the road if you have 350 pounds of weight in the car. What if you're driving by yourself?

One of the training videos I showed my students every year had to do with the things that go wrong with alignments. It was produced by the nation's leading alignment computer manufacturer. One of those related to a Ford with independent rear suspension belonging to a traveling salesman. As instructed, he removed everything from the car, then it was aligned to factory specs. He returned a few weeks later with the rear tires worn to shreds. During that time he had been driving around with 300 pounds of samples in the trunk. We know all Ford cars develop horrible tire wear, but this was aggravated by adding the weight in the trunk. Because this was how the car was almost always loaded, it needed to be aligned while that weight was in the car. The customer needs to be informed of the need to realign the car when that weight is no longer normal.

BMW always seems to do things differently than everyone else. It is very uncommon to see a load specified for performing an alignment. Ford specifies adjustments that promote comfort over tire wear so their cars ride better than those of their competitors. Other manufacturers do extensive test-drives that include determining the best alignment settings for the best tire wear while minimizing the compromise between that and comfort and handling. Once they're happy with those factors, they measure the alignment angles, and those become the alignment specifications. They can't account for the loading variables each car owner will experience, so the readings are taken when the car is empty. That is the one time that variable will be the same for every car.

Before I added weight to a car for an alignment, I'd want to know the reason it is specified that way so I can make an informed decision. One of the more important factors relating to an alignment that few of us realize is suspension ride height. This is less a factor with front strut suspension, but it's a real big deal with independent rear suspension. The frame, control arms, spindles, and steering linkages all have very carefully designed-in geometric angles. Those angles minimize how much a tire tips in and out on top as the car bounces up and down over bumps in the road. Those geometric angles change as the car's springs sag with age. Every shop has a small book showing every car model and year, where to take those measurements, and what they should be. The more conscientious mechanics won't take your money for an alignment unless they are allowed to replace the springs to restore ride height first. The numbers on the alignment computer refer to a "static" car that is standing still. It's real easy to make them appear good and "in specs", but that only applies to the car that is standing still. It's the "dynamic" changes the wheels go through that affect handling, braking, comfort, and tire wear. It is expected that dynamic alignment will be right, when driving down the road, when the static alignment is right when on the alignment rack, but that dynamic alignment requires those geometric angles to be correct. That means that even though the numbers on the computer screen say every tire is adjusted perfectly, you can have reduced cornering ability, longer stopping distances, and miserable tire wear when ride height is not correct.

That said, if it appears there does indeed need to be loading in the car during the alignment, it is most likely because there is a big difference between the static and dynamic angles that are too great to be handled by the alignment computer. Either it needs to have the car sitting at a height closer to what it's at when being driven, or some other factor is expected to change with that loading. As a point of interest, some high-end cars lower their ride height automatically above a predetermined road speed. That is how the car is normally driven, but there is no way to set the height there manually during the alignment. That is where this loading might be necessary.

If this loading is necessary, I would make it your responsibility for providing that extra weight. This is not a common request, so the mechanic isn't going to have anything readily available, and what he is able to round up is likely to be dirty or full of grease. He knows you don't want that in your car. You might consider putting a sheet of cardboard on the seats, then large bags of dog food, or perhaps cement blocks.

You might consider completing the adjustments you're doing now, then see how close you got. All alignment computers are capable of making printouts of the results. Every computer I've seen shows the "before" and "after" readings. The "before" readings are the initial readings taken before anything is adjusted or changed. These are the ones that will show how close you got to specs. Most of the angles interact and show up as changed on the "after" readings, so I always highlighted just those I had adjusted. The printout also shows the range of acceptable settings for each adjustment. If the alignment specialist doesn't explain what he did, you can look at that printout, or post a photo of it and I can interpret it for you.

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The alignment computers convert the measurement systems for us, but not in a way they can be directly compared. During the initial setup, we select the way the readings are displayed, for our preference. If we go back to that setup menu and work our way through it, we can change it to a different type of measurement, then the specs displayed on the screen automatically convert to that system.

I acquired the alignment computer I used at the Chrysler dealership through 1999. When I get home, I'll fire it up and look at the specs for your car. Specs displayed in minutes and seconds is like Japanese to me. Degrees is the language I understand, so once displayed in that format, I can describe the specs in terms of tire wear and handling, and how those compare to the specs of other car models.

Oops; I overlooked your first reply. I can't find any reference to a 320i. Is your car a rear-wheel-drive model? If it is, I would expect to see "caster" listed and adjustable.

The negative camber readings mean both front wheels are tipped in on top, quite a bit. The tires will be running on the inner edges when driving straight ahead. This is one of those compromises I mentioned a while ago. When you corner at high speed, one corner of the car will be pushed down, and the resulting changes in the geometric relationship of the suspension parts is expected to move the top of that wheel outward. With more normal camber settings, that would cause the tire to be tipped out on top and running on the outer edge. By starting with the negative camber, that change during high-speed cornering will put the tire closer to straight up and down, so more tread contacts the road surface. This is where you get the better cornering ability but you lose the tire wear when driving straight ahead. Ford is famous for a similar compromise between tire wear and comfort. On some of their front-wheel-drive cars, a pair of tires will only last 15,000 miles if you're lucky, but those cars are much more comfortable than similar competitors' models. You won't know about the tire wear problem when test-driving and comparing models when deciding which one to purchase, but you will notice the difference in comfort.

It is possible no change was made to the front camber adjustments. The few hundredths of a degree difference in the "Before" and "After" readings would be extremely difficult to adjust in. That's like trying to use an ax to split a hair. What is more likely is the springs settled a little from the car being tugged and poked. A little speck of dirt in the turntables could bind one of the marbles it rolls on, then by just touching the door handle, that plate could move a tiny fraction of an inch and let that wheel settle to a different position. Even opening the driver's door a couple of inches will change those camber readings that few hundredths of a degree. These projectors are extremely sensitive. Where we could measure to the eighth of a degree with the old mechanical equipment, and that was good enough for those cars, the computers let us get down to the hundredth of a degree, which has the potential to be too nit-picky. Your mechanic has his computer set up to read two places after the decimal point, like I did. That gets you much more precision, but just breathing on the car can change the readings that much.

Rear camber is also very high negative. I cringe when I see tires tipped in that much, but until I know what the factory specs are, I'll wait with comments about tire wear issues.

The first of the last adjustments is rear toe. Front toe is done last because we need to match the wheels' direction if steering to the that of the rear wheels, and first, the rear wheels have to be adjusted as close as possible to perfectly parallel to the car. Only the "total toe" on one axle affects tire wear on those two tires. Both wheels can be badly misadjusted, but if they're both off the same direction, the total of their two readings can still be good and provide good tire wear. This would be an example of where the rear is steering off to one side, but if we adjust the front wheels to be parallel to those rear wheels, the steering wheel will still be straight. A lot of cars today have threaded links for adjusting rear toe. Those let us dial them in to the perfect adjustment. When both rear toe values are identical, as a pair, they do not steer the rear of the car off-center to either side. That would be 0.00 degrees "thrust angle". On older models, particularly Chrysler and GM front-wheel-drive models, rear toe was adjusted by unbolting the wheel bearing and sticking in a tapered shim to turn that bearing a little. There could be a dozen different shim thicknesses to pick from, but we had to pick the one that got it the closest to perfect as possible. Those usually offered us a choice of "better than it was", "even closer to perfect", "still better", or "too much". It was very rare to hit both rear toe settings perfect, but it was only the "total toe" that had to be close enough to prevent tire wear.

It looks like your rear toe also didn't need to be adjusted. If 0.21" is in specs for total toe, I also would leave it alone. That's close to a quarter inch, which in my mind is a lot, but I'll come back to that later. Being a positive number, it means the fronts of the wheels are a little closer together than the rears of the wheels. Toe-in is specified when road forces are expected to pull the wheels back a little while driving and braking. Toe-out is rarely specified for the rear. When it is, it is usually because it is expected to compensate for some change that takes place during hard acceleration or some other condition that is frequently encountered. One of those conditions could be the geometric changes the suspension parts go through under various driving conditions.

Your two rear individual toe readings are not equal, but their difference is much too little to discuss. The left rear wheel is turned toward the center of the car by 0.10 degrees more than the right one. If everything else was not a variable, that difference might equate to your steering wheel being turned to the right by half an inch. Over all, the rear axle is steering that end of the car off to the right just a fuzz. That would make the car turn slightly to the left, and you compensate for that by turning the steering wheel slightly to the right. Once you do that, all four wheels are parallel to each other.

Once rear total toe is close enough, the very last step is to adjust front toe to make total toe perfect for best tire wear, and to match each wheel to the rear wheels so the steering wheel will be straight. If steering parts were replaced, we may need to rough-in some of these adjustment first before we let the computer take the "Before" readings, but unlike your hand tools you started out using, when we adjust front left toe, even though that projector is turning with the wheel, it doesn't affect the rear toe reading, even though the rear projector is using the front one for a reference. Much older mechanical alignment equipment used mirrors and light beams, so if you adjusted the wheel with a mirror, the other wheel's reflected beam incorrectly showed a change had been made too. There was a lot of manual calculations we had to make with that equipment. That isn't an issue with the computerized equipment. So, regardless if anything was changed related to rear toe, it's the front toe that needed some attention. All of the toe readings can also be displayed in degrees, but you have it shown in decimal inches. That is also how I set up my computers. The 0.12" total toe you ended up with on the front is perfect for a lot of car models, especially rear-wheel-drive models. That is very close to 1/8th inch, wheels are closer together at their fronts than at their backs. Both front wheels are steering very slightly toward the center of the car. Road forces and braking forces will tug the tires and wheels back a little, making them perfectly parallel to each other while driving.

You started with 0.36" total toe on the front, most of that on the left wheel. That's three times what you should have. To visualize how that affects tire wear, it helps to exaggerate it for clarity. Imagine if those two wheels were turned toward the center of the car more, and more, and more, until they're turned almost 90 degrees and are trying to roll straight toward each other. With even just a little incorrect toe, we refer to the tire's "leading edge". In our exaggerated example, now it's easy to see the outer edge of the tread is the leading edge. It is the part that comes down the road first.

Now visualize a pencil being held straight up with its eraser sitting on the table or desk top. Push down on the pencil, then drag it sideways across the table. The leading edge will fold under, tear off eraser crumbs, and the trailing edge will lift up off the table. No wear will take place to the trailing edge. The same thing happens to the tire. For each block of rubber on the tread, the leading edge will scrub off, and the trailing edge will lift up off the road surface, so little wear will take place on that part. You can feel that wear when you lightly rub your hand over those blocks of rubber. One way your fingers will glide over those ramps of rubber, and the other way your fingers will catch on the sharp edges. Based on that observation, you can tell the car owner which way the total toe adjustment is off, and you know what to expect to find on the alignment computer. When that wear is bad enough, you can even see it when just standing next to the car. It is also possible to observe that wear by running your hands from side to side across the tread, but I need some time to figure out whether it's caused by excessive toe-in or toe-out.

Also be aware the excessive total toe on the front can cause steering wander and a very tiring car to to drive. The tires will be steering in different directions. By the way, they walk in toward each other or away from each other, until the blocks of rubber can't flex any more, then they snap back and start that all over. That is what causes that feather-edge pattern you feel when running your fingers over the tread. The car can only follow one of the tires. In the U.S, that is usually the right one since roads lean to the right so water will run off. By leaning that way, a little more of the car's weight will shift to the right tire, so it sticks to the road a little more than the left one. Now, when you cross an intersection, or hit a bump on the road, more vehicle weight might momentarily shift to the other tire, then the car wants to follow that one. You have to suddenly correct that change by steering the other way. That is what gives the appearance of steering wander.

Related to that is when driving in a cross-wind. Suppose you have excessive total toe-in like you started with, and both wheels are steering toward the center of the car. If a wind blows from left to right, it pushes on the car body which puts more weight on the right tire. That tire will steer the car to the left, against the wind. That will give a feeling of little reaction to driving in windy conditions. The opposite is much more irritating and miserable when you have excessive toe-out on the front. A wind blowing from left to right puts more weight on the right tire, which already wants to steer to the right. This is where the car over-reacts to a gust of wind. You'll be constantly fighting the steering to keep the car going straight.

Another alignment isn't needed when replacing tires unless there is some other problem or tire wear you're trying to solve first.

One comment about sighting down the sides of the tires. Many cars use rear axles that are not as wide as the front wheels. Early Chevy Novas were one really good example. The outer edges of the rear wheels were four inches closer together than those on the front wheels. When you followed one of those down the road, you could see the front wheel sticking out further than the rear wheel, making it look like the car was dog-tracking. They also had a problem where the locating pin on the rear leaf spring would shear off, then with hard braking or hard acceleration, that side of the axle housing would slide forward or rearward on the spring, also causing dog-tracking. Sometimes it was hard to tell what was a true dog-tracking problem and what was just an illusion.

I figured out this isn't a U.S. Model. It isn't listed on my alignment computer. I did print off the specs for a 325i. I never used to see this very often, but before getting to the specs screen, another illustration does pop up about the loading. I forgot what they said for the rear seats and trunk, but it specified roughly 60 pounds on each front seat. If that is done, the car is aligned, then that weight is removed, different numbers will be displayed. Common sense would say to make those new numbers the specs, then that model could be aligned to those numbers without having to go through that loading procedure. Very few other car manufacturers call for special loading, yet they all know there are going to be people and groceries in the car later.

You are also correct that front caster and camber are not adjustable. Rear toe is adjustable on the 325i by means of a threaded rod, so it can be set very precisely. The rear calls for quite a lot of toe-in, at 0.20", but we don't know if that will improve once the loading is removed. I'm comfortable with front total toe of 0.15", which is just very slightly more than older big, heavy cars and trucks called for.

Your comment about "camber is determined by the suspension components" reminds me of the Mitsubishi-built Dodge Avenger in the late '90s. Only toe was adjustable. Being a front-wheel-drive car, caster didn't enter the picture, and due to using two lower control arms on each side, camber changed very little with cornering or sagged springs, so it only needed to be corrected if parts were worn or damaged in a crash. The problem was about 99 percent of those models had a slight right-hand pull from day one, and they needed to have about a half a degree of camber difference added to make them go straight on right-lane roads. The answer was to replace one of the right lower control arms with a new part number that pushed the bottom of that wheel out a little. I did a few dozen of those, and it solved the pull on every one, but then my question was what if you had to replace that arm later due to wear? Only that offset arm was now available. If you had one of the few that didn't need that offset arm, that is what you were going to get when you ordered the replacement. I suspect that extra half degree of camber change wasn't enough to cause a left-hand pull on those cars that didn't need the offset arm. I never heard of complaints after that.

My other concern is control arms are never all exactly the same. That's why alignments are always necessary when replacing any steering or suspension parts. Apparently these control arms were being built with enough precision to prevent the new one causing a pull, but the car would still need an alignment because if the bottom of the wheel, (bottom of the spindle) changes position by even 1/32", that moves the steering arm on the spindle that same amount, and that changes toe. Toe would have to be tweaked to bring it back to specs.

As for the appearance the negative front camber has disappeared, it might be interesting to watch what happens to those wheels when a friend hops into the car. You're looking at it unloaded, which might be different than when it was being aligned.

Keep me updated on your progress, and keep the questions coming I only know three things, and you asked about one of them.

TV / VCR repair, and teaching Automotive Technology.