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Video History-Suspension 1
Video History-Suspension 2
Video History-Suspension 3
Video History-Suspension 4
Video History-Suspension 5
Video History-Suspension 6
Video History-Suspension 7

Video Undercarriage 1
Video Undercarriage 2
Video Steering Wheel 1
Video Steering Wheel 2
Video Steering Lock
Video Steering
Video Safety Steering
Video Rack Pinion Steering
Video Steering Ratio 1
Video Steering Ratio 2
Video Steering Ratio 3
Video Ball Steering
Video Worm Roller Steering
Video Hydraulic Power Steer. 1
Video Hydraulic Power Steer. 2
Video Electr. Power Steer. 1
Video Electr. Power Steer. 2
Video Electr.-hydraulic Pump
Video Torque (power steer.)
Video Electr. Stab. Program
Video Finger Steering
Video One-piece Track Rod
Video Four Wheel Steering 1
Video Four Wheel Steering 2
Video Four Wheel Steering 3
Video Dry Joint
Video History
Video Suspension control 1
Video Wheel positions
Video Suspension
Video Spring systems
Video Electr. Air Suspension
Video Center of Gravity
Video Oblique/lateral drift angle
Video Elasto-kinematics
Video Elk Test
Video Wheel Bearing 1
Video Wheel Bearing 2
Video Wheel Bearing 3
Video Wheel Bearing 4
Video Ind. pulse sensor
Video Wheel sensor 2
Video Transversal Axis
Video Suspension Carrier
Video Below View
Video Adj. suspension
Video Stabilizer 1
Video Stabilizer 2
Video Double-wishbone 1
Video Double-wishbone 2
Video Double-wishbone 3
Video Air suspension truck
Video McPherson Strut 1
Video McPherson Strut 2
Video McPherson Strut 3
Video McPherson Strut 4
Video Trailing Arm
Video Twist-beam Rear Axle
Video Space Arms
Video Multilink Axle
Video Semi-trailing Arm Axle
Video Rear-wheel Drive
Video Electr. Stab. Program
Video ABS/ESP-Hydr. Unit
Video One-arm Swing. Fork
Video Formula-3 Racing Car
Video Pend. Wheel Suspen.
Video Torson Crank Suspen.
Video DeDion Axle 1
Video DeDion Axle 2
Video Rigid Axle 1
Video Rigid Axle 2
Video Rigid Axle 3
Video Rigid Axle 4
Video Rigid Axle 5
Video Self steering axle
Video Track rod joint
Video Springs
Video Coil Spring 1
Video Coil Spring 2
Video Coil Spring 3
Video Leaf Spring
Video Torsion Bar Spring
Video Rubber Suspension
Video Hydropn. Suspension
Video Air Suspension 1
Video Air Suspension 2
Video Shock Absorber 1
Video Shock Absorber 2
Video Shock Absorber 3
Video Shock Absorber 4
Video Shock Absorber 5
Video Single-tube Damper 1
Video Single Tube Damper 2
Video Double-tube Damper
Video Shock Absorber Piston
Video Friction Absorber
Video Tyres
Video Wheel Positions

Video Tyre Calculation
Video Inch -> mm
Video Slip
Video Axle Load Distrib.
Video Payload Distrib.
Video Roller Resistance 2

Video Wheel suspension 1
Video Wheel suspension 2
Video Wheels 1
Video Suspension 1
Video Suspension 2
Video Suspension 5
Video Steering 1
Video Steering 2

          A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

  Undercarriage 1

Mobility is also one of those magic words. It does actually suggest being mobile, although today's traffic-flow is only too often noted for its lack of mobility. It probably reflects our dreams of agility. Actually, it's rather amusing, that part of the testing, e.g., of modern estate-cars, is the zig-zagging around the pylons. The question asked here is, which car can achieve the highest speed through the course?

Now, I ask you, where does this occur in everyday driving? It does of course, in emergency situations, but for this we have ESP. Also, why are the suspensions being made harder instead of more comfortable, with adaptive damping even in the most reasonable class? Is it the longing for a manageable vehicle?, whereby unfortunately, these are being made larger all the time. It doesn't matter, the suspension must deliver the goods, even though it seems sometimes that the driver ahead of you would prefer to carry the car through the curve.

A short summary: Larger vehicles with more powerful engines should give the impression of being as agile as much smaller ones. Just what is the undercarriage? Where does it begin and above all, where does it end? Ultimately of course, the tyres and the wheels are an integral part of the chassis. Indeed, what has happened to the classical frame, onto which the suspension used to be directly mounted?

It can still be found in trucks, transporters and perhaps also in off-road vehicles. In some cases there may also only be one assembly carrier remaining for the axle. Indeed, this can be found in normal motor cars as well. Parts of the wheel guidance may however, also be mounted directly onto the bodywork or onto the flooring reinforcements. We would like to exclude all the components whose movements are identical to those of the bodywork.

So, we're speaking about the forces or more recently, even about the energy which is transferred from the undercarriage to the bodywork and vice versa. They take effect both length- and crosswise, the former are developed through acceleration and braking, the latter through cornering and, e.g., side-winds. There are two influences which make the tasks of the suspension more difficult: heavy weight and speed, the effectiveness of which can in fact even be squared.

Apart from longitudinal- and lateral forces, rough roads can of course, also put an end to the suspension quality. This example best shows, that in a moving car, one can't see the undercarriage but can certainly feel it. For a long time, the car-buyer wasn't particularly interested in the suspension. In the USA there are generations of cars having the same, unchanged suspension.

Thus, the results of the slalom-tests have at least brought about that the potential buyer still knows very little about suspensions, indeed, he/she reacts quite sensitively to vehicles with unfavourable handling characteristics. There are two important aspects of today's suspension that we haven't yet mentioned, the control-electronics and the testing experiences.

You can find out more about the history of the undercarriage here.
You can read about the various engine positions here.
The variety of all-wheel-drives can be discovered here.
Information about tyres can be found here.
The latest about the elasticity in suspensions can be found here.

Perhaps one could put it this way: The specification sheet is the beginning of all evils. Droves of others concern themselves with the basic demands, like driving dynamics and comfort. The safety standards are certainly closely related to these points. Perhaps one can also include e.g., the operating and the noises in the expression "comfort". Indeed, what does an undercarriage have to do with emission?

The fact that, in the end there is a buyer, may under no circumstances, be deliberately overlooked. And production costs and operating expenses have always been an important factor. It's very probable, that there are still constraints within a platform or a series and there are certainly model-philosophies concerned. Thus, a circle with any number of tangents exists, and in the end, comparisons are drawn as to which predecessor has been surpassed.

With the first conception of a new undercarriage it comes to boundary conflicts. The engineers responsible for the suspension need, e.g., more space for the kinematics. From where can it be taken, maybe from the interior or perhaps the size of the fuel-tank? It's not unusual that the specification sheets even limit the elongation of the steering arms. This is how it was, e.g., when the fuel tank was moved to underneath the rear seat for reasons of more effective accident precautions.

The placement of the tyres in relation to the road is actually the most important point. This is why, first of all, a static motion sequence is simulated and displayed on the computer monitor. What is the position of the wheel in relation to the road, in normal and in the compressed condition? How does it change when the wheels are steered and the bodywork sways more? Taking this into consideration, the most important geometries are specified:

Toe difference
King-pin angle
Scrub radius

If you wish to guide a wheel, you must be familiar with the most important aspects of wheel-controlling. Although a certain axle is mostly taken over for the following model, from time to time there is still the need to change. If e.g., the suspension of the Mini was not taken over for the BMW-1 series, one would have to give some thought to the changeover from rear wheel- to front wheel drive.

Here are a few examples of axle construction:

Rigid axle
Torsion beam
Trailing arm
Mulitilink axle
De Dion axle
Semi-trailing arm
Mc Pherson strut
Double wishbone axle
Outdated axle constructions have not been considered here.

Of course, the behaviour of the undercarriage while driving is more important. At this point, the particularly important position of the centre of gravity plays a role. Should measures be taken, because it is too far to the front or to the rear? Now the suspension engineers are making demands on other teams, that the centre of gravity should be placed as near to the middle and as low as possible. The repositioning of the battery further to the rear could well play a role here.

Two small calculations on the subject ...
Axle load
Axle load distribution

Nowadays, the manufacturers can specify the focal point down to the millimeter. In the above picture, we assume it to be in the middle. This is, by no means, to be taken for granted, if e.g., there is only one person in the car. You can see the momentary centre of rotation and the resulting, very important rolling centre. The higher the centre of gravity now lies, the stronger the tilt of the vehicle is when cornering.

Of course, one can do something about this using suitable measures, e.g., to counter it using a stabilizer, indeed it would have been better to have chosen the suspension kinematics, so that the connecting line between the front- and rear rolling centres passes as close as possible to the centre of gravity.

Once the dynamics begin, the geometric simplicity is over. Also the momentary centre of rotation is, as the name indicates, only determinable in this particular wishbone position. It changes if the wheel-springs are compressed. This can influence almost all the other undercarriage data. Thus, the track-width and the wheelbase are by no means constants. The former is changed e.g., in the above picture, when the springs are compressed.

Actually, one would have to draw a whole bundle of lines, to cover the entire sequence of spring-compression. This can be taken even further, if you have a look at the four-link front suspension. In this case, even the swivel-axel of the individual front wheels begins to wander slightly. 01/14

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2001-2015 Copyright programs, texts, animations, pictures: H. Huppertz - E-Mail
Translator: Don Leslie - Email:

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