Understanding wheel alignment.

[gemithomas]

How many of us have stared at the small peice of paper we get after a wheel alighment with some positive and negative figures written all over. Dont we always wonder of how to really be sure that they have done a right job on the vehicle.

First, just to get some theory into place.

• Camber: Camber is the tilting of the wheels from the vertical when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is positive (+). When the wheel tilts inward at the top, the camber is negative (-). The amount of tilt is measured in degrees from the vertical. Camber settings influence the directional control and the tire wear. Too much positive camber will result in premature wear on the outside of the tire and cause excessive wear on the suspension parts. Too much negative camber will result in premature wear on the inside of the tire and cause excessive wear on the suspension parts. Unequal side-to-side camber of 1° or more will cause the vehicle to pull or lead to the side with the most positive camber.

• Caster: Caster is the tilting of the uppermost point of the steering axis either forward or backward (when viewed from the side of the vehicle). A backward tilt is positive (+) and a forward tilt is negative (-). Caster influences directional control of the steering but does not affect the tire wear and is not adjustable on this vehicle. Caster is affected by the vehicle height, therefore it is important to keep the body at its designed height. Overloading the vehicle or a weak or sagging rear spring will affect caster. When the rear of the vehicle is lower than its designated trim height, the front suspension moves to a more positive caster. If the rear of the vehicle is higher than its designated trim height, the front suspension moves to a less positive caster. With too little positive caster, steering may be touchy at high speed and wheel returnability may be diminished when coming out of a turn. If one wheel has more positive caster than the other, that wheel will pull toward the center of the vehicle. This condition will cause the vehicle to pull or lead to the side with the least amount of positive caster.

• Toe: Toe is a measurement of how much the front and/or rear wheels are turned in or out from a straight-ahead position. When the wheels are turned in, toe is positive (+). When the wheels are turned out, toe is negative (-). The actual amount of toe is normally only a fraction of a degree. The purpose of toe is to ensure that the wheels roll parallel. Toe also serves to offset the small deflections of the wheel support system that occur when the vehicle is rolling forward. In other words, with the vehicle standing still and the wheels set with toe-in, the wheels tend to roll parallel on the road when the vehicle is moving. Improper toe adjustment will cause premature tire wear and cause steering instability

So what? I agree about the theory part. But what the hell are those numbers that i see on the piece of paper. How do i really know that they are the right values that my car should have.

[akbaree]

Those numbers are different for different cars. The Authorized service station for your car should be able to provide those numbers for you.

I had came across this website some months back when I was trying to read about Caster, Camber, and Toe. I thought it might be helpful and so I am posting the link - Caster, Camber, Toe

[CrAzY dRiVeR]

To add to the theory-

• Camber:
• 

• Caster:
• 

• Toe:
  

[CrAzY dRiVeR]

Originally Posted by gemithomas

So what? I agree about the theory part. But what the hell are those numbers that i see on the piece of paper. How do i really know that they are the right values that my car should have.

This is common way of giving wheel alignment report- (This is 4 wheel alignment. Most indian cars have 2 wheel alignment)


For a typical user (not talking about team-bhp'ians), all he might need to see is whether the arrow points in the middle portion. The values are published by the manufacturer as per the design specifications, and all that those guys do, is to correct the values to the specified levels.

[goandude]

How is it that in front engine FW drive cars only toe in can be adjusted, while caster and camber cannot?

[gemithomas]

Originally Posted by CrAzY dRiVeR

This is common way of giving wheel alignment report- (This is 4 wheel alignment. Most indian cars have 2 wheel alignment)


For a typical user (not talking about team-bhp'ians), all he might need to see is whether the arrow points in the middle portion. The values are published by the manufacturer as per the design specifications, and all that those guys do, is to correct the values to the specified levels.

THanks a lot for bringing it in. Shouldnt all the colours be green after a proper alignment work? Thats one aspect that confuses me now and again.

Another thing is what is the correct values that my Fiat Adventure should have. The guys fix the computer to Fiat Palio Weekender while doing the adjustments. I suppose the Adventure has different setitings than the weekender. Luckily the computer does not realize that fiat has something that was called an adventure. Can someone tell me how to know that the figures after alignment are the correct ones.!!!!

[gemithomas]

Originally Posted by goandude

How is it that in front engine FW drive cars only toe in can be adjusted, while caster and camber cannot?

i think i see readings for all three aspects on the alignment reports!!!

[anandpadhye]

You can read your car manual and tell the alignment person what the right values for your car are (if you are not sure if he/his software knows the setpoint values for your car).

[gbpscars]

good thread indeed.

a question:
when my friend's OHC went through a suspension bush change (both front and rear), he took it to a wheel alignment centre, and only the front wheels were aligned.

please let me know if this is right practice.

[breezydrive]

what effect does tyre size variation has on alignmant?

[breezydrive]

I really do not know,what to do with the piece of paper (having camber,toe- in,...) as the guy sets the machine for the stock car whereas in my car wheel dia. has 2% variation

[Sam Kapasi]

Originally Posted by CrAzY dRiVeR

Most indian cars have 2 wheel alignment

Originally Posted by gbpscars

and only the front wheels were aligned.

please let me know if this is right practice.

I would assume so after reading that.

[mobike008]

Originally Posted by gbpscars

good thread indeed.

a question:
when my friend's OHC went through a suspension bush change (both front and rear), he took it to a wheel alignment centre, and only the front wheels were aligned.

please let me know if this is right practice.

I think most of the sedans needs 4 wheel alignment done. If i recall correctly, i got mine done about a couple of months ago and it was done for front and back. I know that small cars like Maruti, Zen, Wagon R etc needs only front 2 wheels to be aligned

[gd1418]

Everytime my Scorp or Safari rolls in for alignment, only the front portion is adjusted although they attach the IR device to the rear wheels as well.

Any comments?

[CrAzY dRiVeR]

Originally Posted by goandude

How is it that in front engine FW drive cars only toe in can be adjusted, while caster and camber cannot?

Originally Posted by gemithomas

THanks a lot for bringing it in. Shouldnt all the colours be green after a proper alignment work? Thats one aspect that confuses me now and again.

For all cars, toe is adjustable. However, castor and camber may or may not be adjustable as per design. Toe angles change because of the error in the steering angles of the two wheels on taking a turn.

In WagonR, i was pointed out that camber and toe could be adjusted. And an incorrect value of camber is due to worn parts!

Originally Posted by gbpscars

good thread indeed.a question:
when my friend's OHC went through a suspension bush change (both front and rear), he took it to a wheel alignment centre, and only the front wheels were aligned.
please let me know if this is right practice.

As far as i know (within my limited knowledge), OHC had independent rear suspension, and 4-wheel alignment should be right practice.