Weissach axle
Encyclopedia
The Weissach axle is a special rear suspension arrangement devised for the Porsche 928
. The goal of the Weissach axle was to eliminate lift-throttle oversteer by allowing the rear suspension to adjust itself during cornering maneuvers.
The Weissach axle is a variant of the semi-trailing arm
suspension. The tendency of a vehicle to oversteer when decelerating is compounded by the compliant bushings found in most trailing arm suspensions. When the vehicle is decelerating, the trailing arm pivots towards the rear as the wheel is "pulled" backwards relative to the chassis. This results in toe out
, which makes the vehicle unstable.
For the Weissach axle, the front pivot bushing of the trailing arm is replaced by a short link. In this arrangement, when the vehicle decelerates and the wheel is "pulled" back, the result is toe in
. This adds to stability and thus, reduces oversteer.
A similar, but simpler concept to the Weissach axle is seen in the rear suspension of the second generation Mazda RX-7
. Instead of an extra link, a special bushing is used in the same position in the lower control arm to perform a similar function.
Suspensions with this or a similar function are sometimes called "passive rear steer". The concept of passive rear steering has fallen out of favor for new car designs, as semi-trailing arm suspensions have almost completely given way to multi-link
designs with dedicated toe control arms.
, where the research centre of Porsche
is located and the axle was developed.
Porsche 928
The Porsche 928 was a sports-GT car sold by Porsche AG of Germany from 1978 to 1995. Originally intended to replace the company's iconic 911, the 928 attempted to combine the power, poise, and handling of a sports car with the refinement, comfort, and equipment of a luxury sedan to create what some...
. The goal of the Weissach axle was to eliminate lift-throttle oversteer by allowing the rear suspension to adjust itself during cornering maneuvers.
The Weissach axle is a variant of the semi-trailing arm
Trailing arm
thumb|220px|Trailing arm rear suspension of [[Front-engine, front-wheel drive layout|FF]] carsA trailing-arm suspension is an automobile suspension design in which one or more arms are connected between the axle and the chassis. It is usually used on rear axles...
suspension. The tendency of a vehicle to oversteer when decelerating is compounded by the compliant bushings found in most trailing arm suspensions. When the vehicle is decelerating, the trailing arm pivots towards the rear as the wheel is "pulled" backwards relative to the chassis. This results in toe out
Toe (automotive)
In automotive engineering, toe, also known as tracking, is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e. both...
, which makes the vehicle unstable.
For the Weissach axle, the front pivot bushing of the trailing arm is replaced by a short link. In this arrangement, when the vehicle decelerates and the wheel is "pulled" back, the result is toe in
Toe (automotive)
In automotive engineering, toe, also known as tracking, is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e. both...
. This adds to stability and thus, reduces oversteer.
A similar, but simpler concept to the Weissach axle is seen in the rear suspension of the second generation Mazda RX-7
Mazda RX-7
Series 1 is commonly referred to as the "SA22C" from the first alphanumerics of the vehicle identification number. This series of RX-7 had exposed steel bumpers and a high-mounted indentation-located license plate, called by Werner Buhrer of Road & Track magazine a "Baroque depression."In 1980...
. Instead of an extra link, a special bushing is used in the same position in the lower control arm to perform a similar function.
Suspensions with this or a similar function are sometimes called "passive rear steer". The concept of passive rear steering has fallen out of favor for new car designs, as semi-trailing arm suspensions have almost completely given way to multi-link
Multi-link suspension
A multi-link suspension is a type of vehicle suspension design typically used in independent suspensions, using three or more lateral arms, and one or more longitudinal arms....
designs with dedicated toe control arms.
Name
It is named after the town of WeissachWeissach
Weissach is a municipality in the district of Böblingen in Baden-Württemberg in Germany.The Weissach axle is named after the town, where the research centre of Porsche is located....
, where the research centre of Porsche
Porsche
Porsche Automobil Holding SE, usually shortened to Porsche SE a Societas Europaea or European Public Company, is a German based holding company with investments in the automotive industry....
is located and the axle was developed.
External links
- AutoZine Technical School site
- UK Car - Weissach axle description and diagram.
- Porsche 928 history