Car geometry: some concepts

What is the geometry of the car? Why is it important and what are the consequences of misconfiguration? Let's discover together some fundamental points of this concept of geometry.

What is taken into account in this case?

The geometry of the vehicle is consistent with the design and chassis settings. Indeed, the wheels must be positioned with millimeter precision for optimal driving conditions. The slightest deviation will have different and varied consequences, which we will see later.

This is what geometry includes:

Parallelism

The question here is that the wheels are perfect

parallel to each other

... This is undoubtedly the easiest idea to understand (see appendix here). If it is not perfect, then we will talk about pinching and opening. Daring sidewalk can distort the front axle and the wheels will no longer be parallel. If it rolls "duck", then, as a rule, the inner part of the tires wears out faster, otherwise it will be the outer part (easily visible in comparison with others).

Camber angle

This corresponds to the tilt of the wheel relative to the road as viewed from the front. See here for more information.

Hunting angle

Corresponds to the inclination of the axis of the ball joints.

seen in profile

... It is measured

angle

or

compensate

... If it goes to the front of the car (in the diagram, the hood, therefore, will be on the right), it is considered positive (in most cases). Negative is written on the back.

The angle allows for stability, but at the same time increases understeer. Therefore, it should not be excessive. Traction and thrust settings vary greatly.

Steering angle / Offset from ground

It corresponds to the inclination of the axis of the ball joints, which turns the wheel relative to the road,

seen from the front

... It is "slightly the same" as the caster angle, but seen from the front. The ground offset is positive if the end (down) of the dashed line is to the right of the end of the white dashed line. Therefore, negative if vice versa.

This assembly improves steering by ensuring that it naturally returns to the middle when driving (for example, after turning to avoid sticky steering). In addition, it avoids misdirection when working on chaotic ground (unevenness does not change direction).

Here's a real story for you to tell

Dive and tilt protection angles

They indicate the inclination of the undercarriage relative to the road (suspension arm / triangle). Anti-diving corresponds to the front axle and anti-no-up to the rear axle.

The fact that the undercarriage is sloping allows you to limit the roll effect during braking (a car that crashes into the front of the car) or even to dodge with acceleration (the front rises when accelerating).

How does geometry go wrong?

Several factors can interfere with the performance of your chassis, front or rear. Because if the article is oriented mainly towards the front axle, the other also needs to be adjusted and therefore can also go wrong.

There are two main factors:

• Repetitive impacts (bumpy road, sidewalks too strong, etc.)
• Wear and replacement of some running gear silent blocks

What can be fixed?

Not all items mentioned above are adjustable! This is usually limited to parallelism и convex and sometimes (less often) hunting angle (via steering rod).

Consequences of bad geometry?

The geometry of the vehicle is an important element for several reasons, as the consequences of a malfunction are so many:

• Less efficient road behavior with sometimes strange vehicle response
• Uneven and / or faster tire wear
• Increased fuel consumption due to increased tire drag on the road (a car that rolls a duck will need more energy to move forward as unaligned tires tend to brake the car, as when skiing with the beginner's method of crossing them).

Geometry cost?

Calculate about one hundred euros to correct its geometry. For control it is rather 40 euros.

Do your geometry yourself?

Our partner GBRNR wanted to experience it, and here it is:

🚙Rodius 🚙 Make the house parallel, possibly ❓ Rear axle Ep.11

Is this article missing information? Feel free to indicate this at the bottom of the page via comments!

All comments and reactions

Dernier comment posted:

Laurent83500 (Date: 2021, 09:19:17)

Hi,

Hope you are fine :)

can we carry out a survey even if the tires are worn out?

because on the left side of the tire in 4 lanes I have the following dimensions:

1,9 mm / 2,29 mm / 3,5 mm / 3,3 mm

since i got my 208 i have never done geometry yet: /

Thank you!

Il I. 3 reaction (s) to this comment:

• Administrator SITE ADMINISTRATOR (2021-09-21 11:07:01): No problem ;-)

  And I hope that you are doing well too, although I do not quite understand who I am dealing with ;-)

  Go A +, dear virtual friend!

• laurent83500 (2021-09-21 14:24:20): Since 2013, I regularly consult and I write a lot of comments, but since I change my nickname often, it should definitely be to get to know me: D

  good afternoon 😉

• Administrator SITE ADMINISTRATOR (2021-09-27 10:24:40): Thanks for this light ;-)

  I also admit that it is not always easy to hold back people passing because there is a lot to and fro.

(Your post will be visible under the comment after verification)

Write a comment

How much did the last revision cost you?