Wheel alignment- a good read
10-08-15, 06:17 AM
#2
Lexus Champion
ALIGNMENT TIPS
Proper suspension alignment is critical to the handling of any car. Without knowing what you drive, we can’t give you specific advice on alignment. Every car is somewhat different in both what it requires and what can be adjusted on it. Every car does have the same alignment metrics, however… whether they can be easily adjusted on that car or not. There are also common typical settings for these metrics for performance driving. These basic concepts will be discussed below.
What is Camber?
This is the one you’ve probably heard the most about. That’s because it has a lot to do with good cornering. Camber is the angle that the top of the tire leans away from the center of the car. For our purposes, what we really want is for the top of the tire to lean toward the center of the car. This is called negative camber. Negative camber is good! If camber is negative when the car is pointed forward and at rest (static camber), it will be closer to zero on the outside wheel in a corner. In plain English that means that the contact patch of the tires that most of the car’s weight is on when you are turning will be almost perfectly flat on the pavement. See, I told you it was good!
What is Toe?
You may have heard of this one, too. Toe is the angle that the front of the tire is pointed inward from straightforward. It’s great fun to play with. You might think that zero toe (having the wheels pointed straight forward) would be the way to go to keep the car going straight. Well, not quite. For straight-line stability, a little bit of toe-in is the answer. For quicker steering response, toe-out does the trick. When we get into specifics, you’ll learn that a good alignment may use a little of each.
What is Caster?
Not quite as popular to discuss, but still very important. Caster is the angle that the center of the steering axis is tilted forward. Think of the front wheels on a typical shopping cart. The “steering axis” on those wheels is tilted to the rear (negative caster), making it almost effortless to steer a shopping cart, and giving it no inherent desire to roll in a straight line. The opposite example would be a “chopper” style motorcycle with long forks going to the front wheel. The steering axis is tilted WAY back on this bike (positive caster) and it will have the tendency to go straight at the expense of making it a bit harder to turn. The basic effects are exactly the same on your car, but there may be another side effect if your car has a double-wishbone suspension. This type of suspension will gain a little bit of negative camber when it compresses. If you have more caster, you get more of a gain in negative camber under compression. For this reason, you will often see people recommending “maximum attainable positive caster”. More about that later.
That’s it, folks. Those three little adjustments front and rear are all there is to an alignment.
Factory Alignment Specs
Now that you know what the adjustments are, and have a little understanding of what they do… where do you want to set them??? Let’s start by looking at the factory alignment specs. Where did the factory intend for you to set things? Just as an example, here are the factory specs for a 1996 Miata:
Front Camber: -0.6 to +1.4 degrees
Front Caster: +3.4 to + 5.4 degrees
Front Toe: -0.05 to +0.35 degrees
Rear Camber: -1.7 to +0.3 degrees
Rear Caster: there is no steering and thus no caster (you knew that, right?)
Rear Toe: -0.05 to +0.35 degrees.
There ya go. If you drive a Miata, set your alignment to dead center of those specs and you’ll have a car that will handle adequately for the “typical” driver, not cause undue tire wear for the “typical” driver, and otherwise be fairly safe and predictable. If you never experimented with a “better” alignment, you’d never know the difference. But… if you like to explore the limits of your car’s handling on a regular basis, there is more there for you. Much more. And all it takes is a couple turns of your alignment tech’s wrench.
This would be a good time to mention that alignments from the factory or even from the average local alignment shop could be pretty much ANYWHERE within the factory specs. If you’re serious about handling, ask around and find an alignment shop that will do an alignment to YOUR exact specs without question and with a big ol’ smile on their face. Even if you have a brand new car with 200 miles on it, it will benefit from a good alignment. You’ll be glad you did.
Performance Alignment Specs
So whaddaya do if you want a “performance” alignment? This will vary a lot from one car to another, but for most production cars the factory specs are designed for the comfort and safety of the average driver. You’re not the average driver! Your preferred performance alignment settings will likely be OUTSIDE of the factory specs. If you’re not comfortable with that and can’t find any guidance from people who are experienced with your particular car, the “performance edge” of your factory specs might be a good baseline to start with.
Best would be to seek out some “been there, done that” experience. For the Miata, that comes from Miata.Net. There you will find the infamous “Miq spec” alignment by Miq Millman. Miq has written a very good article, similar to this one, that has become the starting point for many Miata suspension tweakers, myself included. Here’s what Miq recommends:
Front Caster: +4.7 to +5.5 (what ever the maximum attained is)
Front Camber: -0.6 to –0.8
Front Toe: 1/16” per side, or 1/8” total toe out
Rear Rear Camber: -1.1
Rear Toe: 1/16” per side, or 1/8” total toe in or zero
If you look closely at the Miq specs compared to the stock specs, you’ll notice that Miq is basically putting you on the performance edge of the factory specs. This is a great place to start for a street-driven car. But you can further refine these specs to meet your own personal driving needs. Let’s dissect the Miq spec and discuss why each spec was chosen and in what way you might want to change it.
Camber Adjustment
Let’s start with a couple quick facts about camber. As mentioned above, negative camber is good.
As evidenced by the Miq spec pushing slightly beyond the factory spec, you really do want a fair amount of negative camber for good handling. Why not just max it out and go with as much as you can get? Well, it depends on your driving habits. If you do a lot of straight-line highway driving, you can have “too much” negative camber and it will show as excessive wear on the inside edges of your tires. However, if you don’t do as much highway driving, and tend to do a lot of hard cornering on the street (not that I would ever advocate such a thing) and/or autocross regularly, you can get away with a lot more negative camber and your tires will wear evenly due to your driving style. If that’s the kind of driver you are, you can get away with up to about –1.8 to –2.0 degrees maximum without uneven tire wear.
Very important note about camber here. The difference between front and rear camber settings can be used to tune the handling balance of the car to over or understeer. On a typical Miata, you will want to maintain very near a half degree more camber in the rear than in the front. So, if you’re planning to max out the rear camber at –2.0, you’ll want to set the front at –1.5. Maintain that camber differential and you’ll be a happy neutral-steering camper. Other well-balanced RWD cars should be similar. FWD cars will be wildly different!
Front Caster Adjustment
Factory spec is about +3.4 to +5.4. Miq and others recommend either about 5.5 or “as much as you can get”. These guys are overlooking two things: 1) It is possible for the caster to be set at +7 degrees or more! 2) Too much caster is not good for a car without power steering.
My recommendation is to stay within or at least very near the factory spec. More caster means more negative camber in a turn… but it also means more steering effort. The steering effort isn’t such a big deal with power steering, but if you happen to have a car with manual steering it simply can’t be overlooked. Less caster will give the steering a light, easy feel. More caster makes the steering feel heavy and hard to turn. If you have manual steering, you’ll be happier if you keep the caster set at the low end of your factory spec. With power steering, take it on up to the top of your factory spec, but I’m not so sure about “more is better” beyond that.
Front Toe Adjustment
As previously mentioned, toe in will make the car feel more stable and on-center, toe-out will make the car more eager to turn. We like our cars to turn sharply for autocrossing, so a little bit of toe out is good. How much is a matter of opinion and driving style. Most people who do mostly street driving will stick with 1/16-1/8” per side (that equates to about -0.05 to -0.10 degrees). If you do a lot of autocrossing, you might want a little more toe out for even quicker steering response. But be aware that more toe out WILL cause greater tire wear. (one of my technical advisors told me to reiterate that point) Be aware that more toe out WILL cause greater tire wear.
Front toe is the one alignment setting that is truly simple to adjust. If you’re adventurous, you can actually play with this one yourself. Just loosen the locknut on the tie-rod and adjust the tie-rod as needed. If you are going to mess with it, be sure to mark where things are set before you begin and be sure to adjust both sides by the same amount. A half-turn will make a noticeable difference. This adjustment has no effect on other adjustments.
Rear Toe Adjustment
All the rules we talked about for front toe also apply to rear toe. There is the added element of the rear of the car being the end that we really don’t like to lose control of, however! For this reason, most sane people don’t opt for toe out in the rear. In fact, because the suspension bushings on many cars allow the toe setting to move outward just a bit under acceleration, a little bit of toe in is preferred. If you go with the Miq spec of 1/16” toe in, your rear toe will NEVER go positive, and that’s a good thing. We all like nice quick steering response, but we also like predictability. If you’re setting a car up for either track use or highway driving at imprudent speeds (nope, I’d never advocate that, either), you may even want a little more toe in. Going up to 1/8” (0.10 degrees) toe in will make the car much more stable at speed. But… more than that will cause problems like annoying wheelspin when you get on it from a stop.
Remember: Experience and experimentation are the only way to find your preferred alignment. There is no single alignment that is “right” for everyone, even if they drive exactly the same car. Every driver is different, and the alignment must be tuned to the driver’s preference. Good luck!
Proper suspension alignment is critical to the handling of any car. Without knowing what you drive, we can’t give you specific advice on alignment. Every car is somewhat different in both what it requires and what can be adjusted on it. Every car does have the same alignment metrics, however… whether they can be easily adjusted on that car or not. There are also common typical settings for these metrics for performance driving. These basic concepts will be discussed below.
What is Camber?
This is the one you’ve probably heard the most about. That’s because it has a lot to do with good cornering. Camber is the angle that the top of the tire leans away from the center of the car. For our purposes, what we really want is for the top of the tire to lean toward the center of the car. This is called negative camber. Negative camber is good! If camber is negative when the car is pointed forward and at rest (static camber), it will be closer to zero on the outside wheel in a corner. In plain English that means that the contact patch of the tires that most of the car’s weight is on when you are turning will be almost perfectly flat on the pavement. See, I told you it was good!
What is Toe?
You may have heard of this one, too. Toe is the angle that the front of the tire is pointed inward from straightforward. It’s great fun to play with. You might think that zero toe (having the wheels pointed straight forward) would be the way to go to keep the car going straight. Well, not quite. For straight-line stability, a little bit of toe-in is the answer. For quicker steering response, toe-out does the trick. When we get into specifics, you’ll learn that a good alignment may use a little of each.
What is Caster?
Not quite as popular to discuss, but still very important. Caster is the angle that the center of the steering axis is tilted forward. Think of the front wheels on a typical shopping cart. The “steering axis” on those wheels is tilted to the rear (negative caster), making it almost effortless to steer a shopping cart, and giving it no inherent desire to roll in a straight line. The opposite example would be a “chopper” style motorcycle with long forks going to the front wheel. The steering axis is tilted WAY back on this bike (positive caster) and it will have the tendency to go straight at the expense of making it a bit harder to turn. The basic effects are exactly the same on your car, but there may be another side effect if your car has a double-wishbone suspension. This type of suspension will gain a little bit of negative camber when it compresses. If you have more caster, you get more of a gain in negative camber under compression. For this reason, you will often see people recommending “maximum attainable positive caster”. More about that later.
That’s it, folks. Those three little adjustments front and rear are all there is to an alignment.
Factory Alignment Specs
Now that you know what the adjustments are, and have a little understanding of what they do… where do you want to set them??? Let’s start by looking at the factory alignment specs. Where did the factory intend for you to set things? Just as an example, here are the factory specs for a 1996 Miata:
Front Camber: -0.6 to +1.4 degrees
Front Caster: +3.4 to + 5.4 degrees
Front Toe: -0.05 to +0.35 degrees
Rear Camber: -1.7 to +0.3 degrees
Rear Caster: there is no steering and thus no caster (you knew that, right?)
Rear Toe: -0.05 to +0.35 degrees.
There ya go. If you drive a Miata, set your alignment to dead center of those specs and you’ll have a car that will handle adequately for the “typical” driver, not cause undue tire wear for the “typical” driver, and otherwise be fairly safe and predictable. If you never experimented with a “better” alignment, you’d never know the difference. But… if you like to explore the limits of your car’s handling on a regular basis, there is more there for you. Much more. And all it takes is a couple turns of your alignment tech’s wrench.
This would be a good time to mention that alignments from the factory or even from the average local alignment shop could be pretty much ANYWHERE within the factory specs. If you’re serious about handling, ask around and find an alignment shop that will do an alignment to YOUR exact specs without question and with a big ol’ smile on their face. Even if you have a brand new car with 200 miles on it, it will benefit from a good alignment. You’ll be glad you did.
Performance Alignment Specs
So whaddaya do if you want a “performance” alignment? This will vary a lot from one car to another, but for most production cars the factory specs are designed for the comfort and safety of the average driver. You’re not the average driver! Your preferred performance alignment settings will likely be OUTSIDE of the factory specs. If you’re not comfortable with that and can’t find any guidance from people who are experienced with your particular car, the “performance edge” of your factory specs might be a good baseline to start with.
Best would be to seek out some “been there, done that” experience. For the Miata, that comes from Miata.Net. There you will find the infamous “Miq spec” alignment by Miq Millman. Miq has written a very good article, similar to this one, that has become the starting point for many Miata suspension tweakers, myself included. Here’s what Miq recommends:
Front Caster: +4.7 to +5.5 (what ever the maximum attained is)
Front Camber: -0.6 to –0.8
Front Toe: 1/16” per side, or 1/8” total toe out
Rear Rear Camber: -1.1
Rear Toe: 1/16” per side, or 1/8” total toe in or zero
If you look closely at the Miq specs compared to the stock specs, you’ll notice that Miq is basically putting you on the performance edge of the factory specs. This is a great place to start for a street-driven car. But you can further refine these specs to meet your own personal driving needs. Let’s dissect the Miq spec and discuss why each spec was chosen and in what way you might want to change it.
Camber Adjustment
Let’s start with a couple quick facts about camber. As mentioned above, negative camber is good.
As evidenced by the Miq spec pushing slightly beyond the factory spec, you really do want a fair amount of negative camber for good handling. Why not just max it out and go with as much as you can get? Well, it depends on your driving habits. If you do a lot of straight-line highway driving, you can have “too much” negative camber and it will show as excessive wear on the inside edges of your tires. However, if you don’t do as much highway driving, and tend to do a lot of hard cornering on the street (not that I would ever advocate such a thing) and/or autocross regularly, you can get away with a lot more negative camber and your tires will wear evenly due to your driving style. If that’s the kind of driver you are, you can get away with up to about –1.8 to –2.0 degrees maximum without uneven tire wear.
Very important note about camber here. The difference between front and rear camber settings can be used to tune the handling balance of the car to over or understeer. On a typical Miata, you will want to maintain very near a half degree more camber in the rear than in the front. So, if you’re planning to max out the rear camber at –2.0, you’ll want to set the front at –1.5. Maintain that camber differential and you’ll be a happy neutral-steering camper. Other well-balanced RWD cars should be similar. FWD cars will be wildly different!
Front Caster Adjustment
Factory spec is about +3.4 to +5.4. Miq and others recommend either about 5.5 or “as much as you can get”. These guys are overlooking two things: 1) It is possible for the caster to be set at +7 degrees or more! 2) Too much caster is not good for a car without power steering.
My recommendation is to stay within or at least very near the factory spec. More caster means more negative camber in a turn… but it also means more steering effort. The steering effort isn’t such a big deal with power steering, but if you happen to have a car with manual steering it simply can’t be overlooked. Less caster will give the steering a light, easy feel. More caster makes the steering feel heavy and hard to turn. If you have manual steering, you’ll be happier if you keep the caster set at the low end of your factory spec. With power steering, take it on up to the top of your factory spec, but I’m not so sure about “more is better” beyond that.
Front Toe Adjustment
As previously mentioned, toe in will make the car feel more stable and on-center, toe-out will make the car more eager to turn. We like our cars to turn sharply for autocrossing, so a little bit of toe out is good. How much is a matter of opinion and driving style. Most people who do mostly street driving will stick with 1/16-1/8” per side (that equates to about -0.05 to -0.10 degrees). If you do a lot of autocrossing, you might want a little more toe out for even quicker steering response. But be aware that more toe out WILL cause greater tire wear. (one of my technical advisors told me to reiterate that point) Be aware that more toe out WILL cause greater tire wear.
Front toe is the one alignment setting that is truly simple to adjust. If you’re adventurous, you can actually play with this one yourself. Just loosen the locknut on the tie-rod and adjust the tie-rod as needed. If you are going to mess with it, be sure to mark where things are set before you begin and be sure to adjust both sides by the same amount. A half-turn will make a noticeable difference. This adjustment has no effect on other adjustments.
Rear Toe Adjustment
All the rules we talked about for front toe also apply to rear toe. There is the added element of the rear of the car being the end that we really don’t like to lose control of, however! For this reason, most sane people don’t opt for toe out in the rear. In fact, because the suspension bushings on many cars allow the toe setting to move outward just a bit under acceleration, a little bit of toe in is preferred. If you go with the Miq spec of 1/16” toe in, your rear toe will NEVER go positive, and that’s a good thing. We all like nice quick steering response, but we also like predictability. If you’re setting a car up for either track use or highway driving at imprudent speeds (nope, I’d never advocate that, either), you may even want a little more toe in. Going up to 1/8” (0.10 degrees) toe in will make the car much more stable at speed. But… more than that will cause problems like annoying wheelspin when you get on it from a stop.
Remember: Experience and experimentation are the only way to find your preferred alignment. There is no single alignment that is “right” for everyone, even if they drive exactly the same car. Every driver is different, and the alignment must be tuned to the driver’s preference. Good luck!
Last edited by bagwell; 10-08-15 at 08:45 AM.
10-08-15, 06:30 AM
#3
Lexus Fanatic
Good post. 
I'd add four things. First, some modern suspensions, for various reasons, don't have caster settings......the caster is non-adjustable. Second, rear-wheel alignment settings usually apply only with IRS (Independent Rear Suspension)....meaning that each rear wheel moves up and down independently of the wheel across from it, with no direct physical mechanical connections between them. Cars with a beam or live rear axle usually have fixed settings which are determined by the position of the beam or axle itself. (alignments for this type of vehicle are sometimes less expensive because the technician has to adjust only the front wheels). Third, one reason why some shops can't (or don't) get good settings is not necessarily that the technicians don't know what they are doing, but that the shops don't calibrate the alignment machines often enough. Like wheel-balancing equipment, alignment machines have to be periodically inspected and certified. Fourth, once you actually HAVE one, the best way to KEEP a good alignment is to try and stay on as smooth a road as possible and avoid contact with potholes, curbs, road debris, and sharp bumps. Sharp or strong impacts tend to affect alignment settings. That also means driving over speed bumps as slow as feasible.
I'd add four things. First, some modern suspensions, for various reasons, don't have caster settings......the caster is non-adjustable. Second, rear-wheel alignment settings usually apply only with IRS (Independent Rear Suspension)....meaning that each rear wheel moves up and down independently of the wheel across from it, with no direct physical mechanical connections between them. Cars with a beam or live rear axle usually have fixed settings which are determined by the position of the beam or axle itself. (alignments for this type of vehicle are sometimes less expensive because the technician has to adjust only the front wheels). Third, one reason why some shops can't (or don't) get good settings is not necessarily that the technicians don't know what they are doing, but that the shops don't calibrate the alignment machines often enough. Like wheel-balancing equipment, alignment machines have to be periodically inspected and certified. Fourth, once you actually HAVE one, the best way to KEEP a good alignment is to try and stay on as smooth a road as possible and avoid contact with potholes, curbs, road debris, and sharp bumps. Sharp or strong impacts tend to affect alignment settings. That also means driving over speed bumps as slow as feasible.
Last edited by mmarshall; 10-08-15 at 06:41 AM.
10-09-15, 07:59 PM
#4
Lexus Test Driver
Got new tires & alignment done on the RX recently after having huge challange with vibration. For testing purposes on a smooth two lane country road with nobody around I made multiple passes back & forth and while there was a very slight drift to the left or right it went acceptably far in a straight line. Also did a very quick 90mph test and ZERO vibration. That would have been unthinkable before. Happy camper.
More importantly as Marshall pointed out having the equipment itself working properly is paramount. This is why I don't bat an eye at my trusted mechanic charging what he does. Do it right the first time. .
More importantly as Marshall pointed out having the equipment itself working properly is paramount. This is why I don't bat an eye at my trusted mechanic charging what he does. Do it right the first time. .
10-10-15, 10:34 AM
#5
Most techs at those big chain stores don't really understand alignment. They're paid to turn a wrench until the indicator on the screen turns from red to green. I don't blame them though since their customers are not race car drivers. Heck, most of the time they do not even check the tire pressures prior to the alignment!
10-12-15, 06:51 AM
#6
Super Moderator
Although I am on much flatter and better roads now in Florida, in Mexico City when I lived there from 2002-2008, alignment was a constant word in my vocabulary. You could literally get a computerized one there for about $15 USD equivalent and because I raced there, it was done about once a week. The roads screwed up alignments that badly and I was a big stickler for having everything done to a T so that track time would be as best as it could be.
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