Correct wheel alignment of the car is essential for proper steering control and for prolonging tire life. If the tread wears too quickly or is uneven, the car "pulls" to the right or left, transmits a lot of vibrations while driving, or the steering column does not feel firm, there is very likely a problem with the trim. Follow the instructions in this article to diagnose common causes and correct the most common cause at home: anterior-posterior alignment.
Steps
Part 1 of 4: Preparing to Take Measurements
Step 1. Check the tire pressure
They should be properly inflated before proceeding.
- Tires at the wrong pressure could be the cause of the car's poor performance, so it's worth doing an inspection first; sometimes that's all it takes.
- It is also important because this way you make sure that the buoyancy measurements you will find later are correct.
Step 2. Check the car specifications
Consult the maintenance manual for details on the set-up; you should find numbers that indicate the ideal values of toe, camber and caster.
Write down these numbers. You may not know their meaning, but don't worry as they will be described later in the article; for now, write them down correctly
Step 3. Check the front shock absorbers
If they are too soft or show signs of wear, they could be the source of the problem. Just like tire pressure related anomalies, suspension anomalies can also alter the accuracy of your measurements, so you need to correct them before continuing.
- Bring the machine to a flat surface, lift the front and secure it on jacks; make sure the steering lock is not engaged.
- The easiest way to check the suspension condition after lifting the car is to grab each wheel and shake it both horizontally and vertically. If it doesn't move too much, the shock absorbers are probably in good condition; if not, they could be the source of the anomalies you noticed.
- If the suspension is soft, you need to replace worn components; this means changing the ball joints, arms, bushings, transmission, steering bearings or tie rod ends.
- Unless you are experienced with servicing these parts, it is best to take the car to a professional mechanic.
Part 2 of 4: Measuring the toe
Step 1. Determine the correct value
Toe-in is the parameter that indicates the angle formed between the tire and the longitudinal axis of the vehicle; in other words, it represents how much the front edge of the tire is closer to the car than the rear edge when viewed from above. Depending on the car model, the service manual may recommend zero (the wheel is parallel to the longitudinal axis) or slightly positive (the front is closer to the frame than the rear) toe-in to improve stability.
This is the parameter that more than any other is at the origin of many problems and also the simplest to correct in an artisanal way
Step 2. Draw a line
While the car is still raised, keep a small knife, chalk or pen resting in the center of the tread. You need to have a very steady hand and ask a friend to rotate the tire completely, so as to draw a line around the entire circumference. Repeat the same procedure for the tire on the other side.
If there are no areas where the tread is smooth, it may be necessary to hold the chalk or other similar tool suspended with a vice
Step 3. Lower the vehicle
After bringing it back to the ground, push the hood down a few times to stabilize the shock absorbers.
Step 4. Move the car
Drive it forward for at least 3m without locking the steering to make sure the wheels stay straight.
Step 5. Stretch a thread
With the help of an assistant, take a piece of string or wire and spread it between the two lines you drew on the front of the tires, making sure it is parallel to the spindles. Measure the length of the wire and repeat the process on the back of the tires.
As long as you are not using a thread or elastic twine, this method allows you to obtain very precise data
Step 6. Subtract the values
If the distance between the two front lines is less than that of the rear lines, the convergence is positive; vice versa, it is negative; if the values are identical, you have zero convergence.
Rear wheel toe is important for vehicle control and tire wear; it is also important that each front-rear pair is aligned (the front left wheel parallel to the rear left and the same on the right side). You can measure rear toe in a similar way; if you get any abnormal data, you need to have it adjusted by a professional tire dealer. It is important that the rear alignment is corrected before the front one; therefore, if you encounter this type of problem, do not waste time repairing the front toe yourself
Part 3 of 4: Measure the Camber
Step 1. Determine the correct camber value
This is the angle that the wheel makes with the vertical and that you can see by looking at the machine from the front. When the top of the wheel is closer to the vehicle than the base, the camber value is considered "negative"; vice versa, we speak of a "positive" angle. Depending on the model, the manual probably recommends a slightly negative number to improve stability.
Step 2. Cut out a reference triangle
Take a piece of stiff cardboard or wood and make a perfect right triangle that is the same height as the wheels.
Step 3. Place it on the ground
Start at the front of the car and place the base of the triangle on the ground, so that the other side adheres to the center of one of the wheels.
Step 4. Take measurements
There should be a gap between the measuring tool and the rubber, probably at the top. Measure this distance with a ruler or caliper, the resulting value represents the camber.
- Repeat the process with the other front wheel; you should get a value identical to the first and within the tolerance range indicated by the maintenance manual. If not, you need to adjust the camber angle. Follow the same procedure for the rear wheels.
- If you are concerned that these values are incorrect, move the car back and forth just enough to rotate the tires half a turn, then take the measurements again.
- Front or rear camber problems affect the maneuverability of the machine; however, unless you have suffered a serious accident, it is quite rare that this angle is far outside the established parameters. If you need to adjust the camber, proceed first to adjust the toe.
- Generally, you cannot adjust it at home with normal tools; in fact, in most cases it is not possible to modify this angle without bending or replacing some main components. Unless you are experienced in mechanical repairs and have professional tools, do not attempt to do it yourself.
Part 4 of 4: Correcting the Convergence
Step 1. Locate the tie rod ends
The tie rods are the elements that connect the steering system with the wheels; the terminals have an "L" shape and you can sometimes find them near the inside of the wheel.
It is worth consulting the maintenance manual and / or looking at some pictures online to understand what these pieces look like and how they fit on your particular model
Step 2. Loosen the locking nuts
Each terminal is fixed to the respective tie rod through a nut that you have to unscrew with a wrench.
- Remember that some car manufacturers use a reverse threaded bolt on the driver's side for these components - in which case, you have to turn the nut clockwise to unscrew it - while they use a normal threaded bolt for the passenger's side.
- Depending on your steering system, there may also be a clamp that you need to remove from each end, to make sure the bellows seal has not stuck to the inner terminal. Read the manual for more details.
- If it has been a long time since you last adjusted the trim, the threaded parts may offer some resistance, making it necessary to use a little lubricant, such as WD-40, to be able to unscrew them.
Step 3. Make your adjustments
Depending on the type of steering fitted to the vehicle, there are two methods for changing the toe-in.
- If the system is equipped with a rack and pinion, you should rotate the internal terminal on itself, in order to change the negative or positive convergence.
- If the car is equipped with a wishbone system, there should be some adjustment sleeves that you can turn to change the toe. These are delicate components that can be easily damaged, so proceed with caution; there are special tools to rotate the steering rods and avoid damage.
- Whatever system is fitted to your vehicle, remember that the modifications must be spread over two wheels; each arm should be adjusted for half the total variation you want to achieve.
Step 4. Check the convergence again
Tighten the nuts (and clamps, if applicable) and measure the angle following the same method described in the second part of the article; if necessary, make the necessary corrections.
Unless you are well versed in these types of interventions, you will have to proceed by trial and error before getting the correct values
Step 5. Take a road test
Drive for a few kilometers to assess any set-up problems you have corrected (for example the car does not vibrate too much and does not "pull" to one side).
If the anomalies persist, it is likely that a professional mechanic will be required
Advice
- The modern instruments used by tire specialists are the most accurate means of measuring and adjusting the car's trim.
- In addition to camber and toe, the third criterion to consider when recording buoyancy is incidence; this is the angle formed by the steering axis with the perpendicular and can be evaluated by observing the car from the side. It is a very difficult parameter to measure without special tools and it is impossible to adjust it at home; in fact, on many cars it is not possible to modify it without replacing the suspension. If the convergence correction does not solve the problems, it is probable that action must be taken on the incidence; a tire dealer can tell you if it is necessary or even impossible.
- There are devices on the market that allow you to measure the camber; if you run into problems with the method described in the article, you can perhaps succeed with one of these tools.
Warnings
- After lifting the car, check that it is very stable before sliding under it and especially before shaking the wheels to inspect the suspension; if the car crashes, you could be seriously injured and even die.
- The complete set-up of modern cars consists of different angles and distances which must all be respected for safe road holding. If adjustments are made incorrectly, vehicle control is adversely affected and extremely dangerous situations could occur.
