What does an alighnment do?

[Sleeper s13]

I dont want to sound ignorant but i am. I know what it is for the front and rear wheels to be in line but what does it have to do when you adjust camber and toe angle or do you adjust toe? What moving parts are moved and what affect do they have on your handling?

[NISTECH]

tie rods for toe in and out. shims or excentrics for camber and caster which is on the control arms. toe and camber effect tir wear primarily. toe unless excessive does not cause pull or drift. camber will cause pull or drift. caster will cause pull or drift and effect steerabilty(how hard or easy it is to turn the wheels) and return abilty when releasing the sterring wheel after turning.

[Nismo_Freak]

Ahh... good ol alignment racks! Woot!... I aligned my 240 at work on our rack.

[Q45tech]

The factory measures [reverse engineers] the static alignment specs [especially toe] so that the tires are pointed straight when under forward load at speed........the rubber isolation bushings deflect under forward motion.

When you load a car up passengers and trunk, the springs compress roughly 1 inch per 500 pounds [obviously it depends on where the load is [just a driver or 4 passengers and something in the trunk].........as the ride height gets lower the static camber increases [more negative].

The tire performance is best when the tire patch is equalized [shape] UNDER LOAD when stopping, cruising, or accelerating.Aligments job is to set you in the center so that the suspension can perform as best it can at the extremes.

[Nismo_Freak]

The factory measures [reverse engineers] the static alignment specs [especially toe] so that the tires are pointed straight when under forward load at speed........the rubber isolation bushings deflect under forward motion.

When you load a car up passengers and trunk, the springs compress roughly 1 inch per 500 pounds [obviously it depends on where the load is [just a driver or 4 passengers and something in the trunk].........as the ride height gets lower the static camber increases [more negative].

The tire performance is best when the tire patch is equalized [shape] UNDER LOAD when stopping, cruising, or accelerating.Aligments job is to set you in the center so that the suspension can perform as best it can at the extremes.

So is it incorrect to do an alignment while you have a load in the car? IE, person or thing weighing the same as the driver in the driver's seat. The alignment machine does have a feature for pre-load. I've done several alignments for Miata owners with them sitting in the car and the machine calibrated to their weight. I would think this would give the left side, in particular, a slight amount more "center" when loaded down with a driver.

[Sleeper s13]

Thanx. its still a little fuzze but once i see of diagram that better depicts the movement of suspension components i will fugure it out.

[Q45tech]

Take a Q for example the perfect oem camber is -0.7 degrees static [midpoint of range] but with a 170 # driver, the left front drops 0.5" which increases negative camber by 0.3-0.4 degrees.........so loaded camber is say 1.0 degs negative on the drivers side and -0.7 on the passenger side.

My comments assumed brand new bushings in every suspension part including the rear subframe. After a year or two all bets are off.

I think toe and thrust angle would be the most variable on the road..........as you can imagine camber will change in acceleration and braking based on the angle of the body..lift or dive.......and a radial tire needs to be at negative 1.0 to negative 0.5 degrees to achieve the maximal friction.

Suspension camber gain curves are usually set as a compromise between handling and braking.........so a 3" dive would probably increase camber by 2.4 degrees more negative.........why stiffer front springs sometimes improve braking distances -- a little less dive less camber gain.

If you had a chassis dyno you could measure the toe changes on the rear wheels.......set the toe for maximum HP to the road under acceleration......but then you might have the wrong toe under the modest power of 70 mph cruise. Guees you could use chain hoists and measure the pulling forces and equate to acceleration to find the under load toe.

Nissan rear suspension toes in, on braking, toes out in acceleration. Obviously the range of movement increases with age.

Don't forget to set the sway bar preload also as the coupling will be different with a driver and in different directions........on Nissan the bars usually are attached at midpoint of suspension arm so divide by 4 ,a 1/2 inch suspension drop will be a 0.125 " change in the bar position!