I have done my own alignmments for years, 2 boards, a tape measure, and take it for a drive. If it pulls to the left, slows really fast, or if the steering wheel is not centered, I'll work on the car till I get it right. Having worked at 2 dealers, when a car goes on the alignment rack, it's not going down the road, it does not have the driver in it, and it may have a full or empty tank of gas, all these things can change what the alignment is doing on the road.
I have a friend who competes in SCCA and he aligns all his cars every month. He said that even from the factory new cars go quickly out of alignment. The alignment when new is just to roll the car out the door, once springs settle, rubber bushings wear in, that new car can be totally out of alignment.
So this got me to thinking, what is the optimal alignment for MPG? Setting up a car to handle normally pushes the wheel camber out to the sides to get more tire leaning in during the turn. So would this mean on straight roads trying to get the highest mpg, should your tires be straight up and down or cambered out so less of the tire is in contact with the road?
Front wheel drive cars like a little toe out, because they are the drive wheels and want to pull themselves in. Where rear wheel drive cars like a little toe in, because the wheels are being pushed back when rolling down the road.
Now with most cars being able to align the front and the back, where is the alignment sweet spot of lowest rolling resistance?
I also raced SCCA and alingment was critical. Of course race cars have camber plates, can be set up for no bumpsteer, can be squared up using string and 4 jackstands and set toe in/out...all right at the track as long as you have a level surface to work on. The no bumpsteer allows you to change camber without changing toe in/out. I always was in the car with full gear and 1/2 tank of fuel.
For street purposes things that change alingment are worn out parts/slop, potholes, ect. First you must start out with cold running tire pressures where you want them. The tires should be in good shape to get a good alignment. Then you need to lock the steering wheel in the "centered position". You should be able to aling it so that when you are thru the wheel is straight.
For a street car the "static" alignment should be very neutral. Camber should be around .5 degrees, toe should statically be very close to zero...toe out just a tad for front drive and zero or toe in just a tad for rear wheel drive. Caster should be very close to the OEM settings. If you have adjustable Caster, you can still have a straight drving vehicle AND get some camber out for turning. I know some specs take into account the crown of the road so left to right specs can be a bit different.
The best way to fix alignment is to get the shop to give you a print out of your current specs. Take those and factor in what the vehicle is doing now and go from there.
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Bought an 06 Corolla new, back to dealer at 12 k for excessive wear on both front tires on the outside (usually toe). Was told problem was due to not rotating tires (yeah right). At 19k I took it to a friend who was the service manager at another Toyota dealer, with all 4 tires worn badly on the outside now, after I checked the balance, and found I had paid dealer one for four wheel balance and they had not even removed the original weights from the rear tires when the moved them to the front, and they were out of balance by a total of over two ounces. They did balance the tires they moved to the rear.
My friend put it on their high tech alignment machine and took me there to show me the specs. Front total toe was beyond max, although individual wheels were within specs. Rear axle (solid) was out in such a way that both rear wheels were pointing somewhat to the left of where they need to be.
First he replaced the rear axle and adjusted the front toe, but the rear was still out of specs, so he had me drop the car off and took it to a frame shop to have the mounts for the axle shifted enough to get the rear axle pointed in the right direction.
This was a brand new car I bought with 6 miles on the odo, and I have some friends that have bought Toyotas that have the same symptoms as mine.
I sold the Corolla and bought a Del Sol, then found my 94 VX with less than 28k actual miles when I got it in February.
For best mileage the alignment specs should be at the minimum total toe, with camber as close to 0 as is practical (Minimum specs). Camber will be different from one side to the other in the front or the car will drift to the right on roads due to the crown in the road. Generally speraking the specs should be as close to 0 as possible (except caster) while still within specs individually and at the minimum of total spec for both sides.
Theoretically 0 toe would give you the least rolling resistance, but you have to consider that putting force on the wheels can affect the toe. So then you try to set the toe to correct for this, namely on the drive wheels. But how are you going to measure that? A loaded dyno/alignment rack?
As far as camber goes, I'd say you'd want to maximize grip for accelerating from a stop, so camber should be close to zero on the drive wheels. Again you might want to take into account what happens when you hit the throttle. The front of the car lifts up, and this gives you a slight positive camber on most vehicles.
I've got slight negative camber and zero toe, the way the A arms and stub strut are set up on mopars of this era makes for a tendency to go toe out under power... I'm considering giving it slight toe in, because it does tend to grab and/or wander a little under power. However it seems dead on for rolling, I did some rough and ready testing, probable accuracy of within 10% and figured I have a total RR in neutral of 0.032 which works out I think at 0.008/wheel with Kumho/Marshal Ulysses ST touring 205/70R14 tires aired up to 40psi.
Edit: Oh BTW the "MOTOR" repair manuals give a max min and "desireable" for toe, camber, caster etc... I can find those specs for domestic cars up to '86 and light trucks up to '89 if anyone needs them. (I think alldata has the same info online if anyone has a subscription, likewise I think EBSCO Host which has car repair data, that many public libraries give access to, has the same info.)
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Oh BTW the "MOTOR" repair manuals give a max min and "desireable" for toe, camber, caster etc... I can find those specs for domestic cars up to '86 and light trucks up to '89 if anyone needs them.
Good point. Many autos are set up to have a certain 'feel' from the factory, usually for better stability. It's a good idea to know where you're starting from, then adjust from there. My other car is supposed to have 3mm toe in at the rear wheels. Setup this way the car tracks dead straight, unflappable. It doesn't coast so good though.
For cars that toe in/out under power, what do you do if you want to optimize coasting distances? Should it be set it up with zero toe so it coasts good in neutral or a little toe in/out so it has less drag under power? One solution is to get polyurethane suspension bushings so it doesn't flex.
I have been driving my car (a 2002 Corolla) for almost a year with really bad pull to the right. If I were to go 30mph and didn't hold onto the wheel I would be of the road in probably 20ft. I looked under my car to see how I would go about it when I changed my oil and I see no way to make any adjustments. The same goes for the rear. Just like what R.I.D.E. mentioned I see the only way to do it is by machining with the rear, but how do I do the front? I probably have a good 10k miles left on my tires and was going to wait until they were done and then get a whole package new wheels and alignment, so if I could get my alignment better than what is now I would be happy. Even if it isn't perfect.
If anyone knows where I can go online to find a good set of steps to do this or tell me how to do it, I would greatly appreciate it.
I just did my outer ties rods tonight and a self alignment, then thought that the self alignment method was a good thing to share. First I tiestrapped two 4' long metal shelf brackets, (but any STRAIGHT sticks will do), through the rims, to the outside of the wheels pointing out ahead. then measured the distance between them close by the bumper, and then out at the ends. Then you adjust the tie rods (with the steering wheel straight) a little on each side until you get an equal distance at the two measure points, also keeping them pointing equally straight ahead to match the steering wheel. This means that the toe is straight and even since even a slight variation would have the sticks looking like this \ / or this / \
With the extended sticks you can really fine tune it since a little wheel movement makes a big movement on the extended sticks. Just remember to have the car on the ground "loaded" or the adjustment will be off since the wheels toe in when the car is raised, if you adjust it raised it will be toed out when you lower it off the jacks...... not that it happened to me or anything. :rolleyes