The influence of front and rear wheel suspension toe on handling

  • Author: OPONEO.CO.UK

Typically, car toe suspension is not a topica that comes up until something is wrong and is having an influence on the car’s performance, specifically with the tyres, suspension and performance.

In many of these cases, the culprit can often be a misaligned suspension toe, especially in cases when the car starts to pull to one side after meeting a large pothole or curb. If the effect is strong enough, the shaft for the steering system may even be bent, impacting the car wheel alignment, consequently having a negative influence on handling.

How does the toe on a car work?

Before we continue, let’s answer the most obvious question: what is car toe? To answer this, you should know that car wheels are not perfectly parallel. Typically, they are actually slightly toed-in.

To understand why vehicles are designed this way, you should first understand what happens to the front wheels (specifically, when using a front wheel drive vehicle) as it accelerates.

Each wheel generates a certain amount of force, which tries to pull the car in its direction. This situation often seems stable, as these generated forces are balanced on either side of the car. Yet, when the vehicle drives over a bump, one of the wheels gets more grip, leading to instability. The car starts swerving and requires corrections to stay on course.

To avoid having to constantly correct the direction, both wheels are slightly turned inwards. The wheels generate opposing forces but the whole system is stable. Additionally, all the elements of the car suspension system and tyres are pre-loaded as a result, which has a positive impact on handling. However, is it not a flawless system, as it causes slight understeering when taking corners and curves.

What are the symptoms of misaligned wheels?

When a vehicle has a front toe-in, it often has a tendency to straighten the wheels when driving. This is especially visible when driving at high speeds, as the car will stay straight, even if you let go of the steering wheel. This is a desirable effect.

Consequently, letting go of the steering wheel is one of the simplest ways to diagnose any wheel alignment effects or issues. When your car pulls slightly to the left or right, it indicates it is time to control your suspension toe. In other words, the wheel toe is asymmetrical, and this needs to be corrected to its intended, exact symmetry.

Similarly, you should visit a diagnostic station if you have to keep moving your steering wheel to drive straight. This is also true if you find your car turns more easily right, when compared to going left, or vice versa.

This should be done as soon as possible, as driving with an incorrect toe will wear the edge of that specific tyre faster, leading to uneven tyre wear across all of your wheels, as well as diminishing the durability and lifespan of the particular tyre in question.

Improving handling via suspension toe adjustments

It often surprises drivers that, even if a car has no history of any accidents, it can still have an incorrect suspension toe. The alignment can change over time, due to replacements or through simple wear and tear of the suspension system elements, including ball bearings, steering shaft joints and bushings. For this reason, you should always check your wheel alignment is within the recommended range when getting any scheduled diagnostic work done.

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Examples of front wheel suspension toe +0,5°

It is also worth mentioning that the numerical suspension toe value is not as important as the symmetry between the wheels. For example, let’s compare these two example cars:

  • The first car has a right wheel toe of  -0.1° and a left wheel toe of +0.6°.
  • The second car has a suspension toe of  +0.25° on both wheels.

While both of these cars have the same overall toe (+0.5°), the first car will drive unreliably, with different characteristics on either side. The second car, which is symmetrical and balanced, will offer a much smoother experience.

This same principle applies to the rear toe alignment, too. This symmetry is also vital and, in cars with a multilink suspension (such as the Volkswagen Passat B6), where the toe can be adjusted, this is even more vital.

How is the suspension toe in sports cars set up?

With typically roadworthy cars, the factory suspension toe settings are a compromise of various factors, with a special emphasis on ensuring car safety on all surfaces. In motorsports, such as GT racing, where rear wheel drive vehicles are more popular, a slightly different setup is used.

This is completely different in rally cars, where suspension toe adjustments are made according to the road surface in a given section. On smooth tarmac with fast and long curves, the front axle toe is positive, while the rear is zeroed. On loose gravel roads, where the car almost never drives straight, sliding instead from curve to curve, both axles are set to negative. This ensures immediate reaction to steering (at a cost of very nervous driving in straight lines).
Here, the front wheels have a negative toe, while the rear wheel toe in is slightly positive.

However, in rally cars, this is completely different, as suspension toe adjustments are made according to the road surface of the given section. On smooth tarmac, where fast and long curves can be expected, the front axle has a positive toe, while the rear is zeroed (perfectly straight).

On loose gravel, on the other hand, the car almost never drives straight, often sliding from curve to curve. Consequently, both axles are set to negative, ensuring an immediate reaction to steering. As far as real wheel alignment symptoms go, this comes at the cost of more difficult, nervous driving in straight lines, which is why such a setup is impractical and unsafe for regular road use.

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For rally cars, the suspension toe is often adjusted in pit stops before special sections.

The importance of proper wheel alignment is most highlighted by the fact that suspension mechanics often book several days of training in order to find the correct alignment for a given rally event.

Why should i control my suspension toe?

Even though you might not notice anything wrong with your car’s handling, the toe car alignment parameters may still be incorrect. If this is the case, you can experienced an increased rolling resistance, additional tread wear and greater fuel consumption.

Also, you can impede your driving safety, as the car makes frequent, nervous reactions to your steering. While you may get used to it as a driver, it does mean this is typical, acceptable behaviour for your vehicle. Similarly, there are also cases of incorrectly working ESP (Electronic Stability Program) systems, caused by bent steering shafts. When the steering wheel is turned and the car continues to drive straight, the ESP tries to react, as it mistakes this situation for a slide or skid.

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Comments
Re: The influence of front and rear wheel suspension toe on handling
lukee 09/03/2012 Answer

nice nice

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