Talk:Trailing arm

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I've tagged this article for expansion. More details are needed, and only one source is noted (and used although not cited.) Fine source it is, but some more experts could give a hand here... (I could have a try and add something more, but I believe an engineer would be better suited for the task, and I am not one.) --Arny (talk) 17:46, 28 March 2010 (UTC)

yes, it explains "stuff" but doesn't really explain benefits and drawbacks of this suspension component. I'm currently dealing with step out due to bushings combined with this rear suspension. (talk) 02:49, 26 August 2014 (UTC)

Merge proposal: "Weissach axle" into "Trailing arm"[edit]

The "Weissach axle" is a specific application of the semi-trailing arm principle. The article on the Weissach axle is short and can easily fit in the more general article "Trailing arm". Therefore I propose merging "Weissach axle" into "Trailing arm". Sincerely, SamBlob (talk) 05:10, 4 April 2015 (UTC)

Good idea. Greglocock (talk) 06:12, 4 April 2015 (UTC)
  • I'm wary of this. The Weissach axle is obviously independently notable. More to the point, it's significant as an early example of passive rear steering, not as a fairly mundane example of a trailing arm. Andy Dingley (talk) 09:41, 4 April 2015 (UTC)
The Weissach axle is a specific application of the double wishbone principle. Look at -- (talk) 08:44, 29 April 2016 (UTC)
Editing it to change every instance of "trailing arm" to "double wishbone" doesn't change how independent sources have always described it, as a development of a trailing arm. Andy Dingley (talk) 08:59, 29 April 2016 (UTC)
Rear Suspension Exploded.jpg shows an additional joint at the lower arm and an upper arm (no wishbone). Trailing arm axles have no joint between arm and wheel and do not need an upper arm. A simlar thing ist the "BMW-Zentrallenkerachse". (talk) 09:29, 29 April 2016 (UTC)
Europefan, we work by how the sources describe it, not how one editor thinks it ought to be instead. The sources term it a semi-trailing arm, not a wishbone or double wishbone.
It is not a double wishbone. There is no upper wishbone, merely a single link. Without the wide inner base, that is no wishbone.
The lower arm is not a wishbone. Although it looks like a wishbone, it is itself flexible (this is the Weissach innovation). The "forward half" of the "wishbone" shortens under a dive, giving the toe-in movement. The diagrams at the Autozine page show this quite well. The aspect that is like other suspensions is that of the semi-trailing arm, not a wishbone. Andy Dingley (talk) 10:04, 29 April 2016 (UTC)
How can it be a semi-trailing arm, if it needs an upper link? Remember Lotus Europa. It's nearly the same thing, with no toe-in joint in front. Is that a semi-trailing arm supension too? -- (talk) 10:42, 29 April 2016 (UTC)
The Lotus Europa is generally counted as a Chapman strut, mostly because of its origins, where the radius arm became a wishbone. Like the Europa, the Weissach takes its identification primarily from the suspension it developed from: which was clearly an adaptation of an earlier trailing arm, not a wishbone.
There is nothing defining about a semi-trailing arm that says it can't have an outboard joint on the arm, thus requiring additional links to keep the hub carrier upright. Most modern trailing arms are rear suspension for cheap everyday cars, where cost is what matters, and so they use the fewest parts possible, with the hub fixed to the arm. That's never a requirement though - looking mid-century there were many more trailing arm suspensions, the Porsche's own VW Beetle front being a good example, where a hub carrier was jointed to a trailing arm, requiring multiple trailing arms or extra links to control its upper end. Andy Dingley (talk) 10:53, 29 April 2016 (UTC)
Maybe you will like some sources:
  • "Die Hinterachse des 928 war eine absolute Neuheit. Das Besondere an dieser – auch als Weissach-Achse bezeichneten – Doppelquerlenkerachse war ihre vorspurstabilisierende Eigenschaft. Diese wirkte quasi wie eine passive Hinterradlenkung und war damit ein wesentlicher Beitrag zur aktiven Sicherheit des Granturismo." "Doppelquerlenkerachse" means "double wishbone suspension"
  • Jörnsen Reimpell, Fahrwerktechnik, ISBN 3-8023-0505-1, Chapter 3.4 Doppel-Querlenker-Radaufhängung, page 348: "Ebenfalls eine Doppel-Querlenker-Radaufhängung stellt die Weissach-Achse des 1977 herausgekommenen Porsche 928 dar."
"Doppelquerlenkerachse" or "Doppel-Querlenker-Radaufhängung" means "double wishbone suspension"
Sorry for the german sources, but those are most common my country. -- (talk) 13:15, 29 April 2016 (UTC)
Well those sources are wrong since quite clearly the upper arm is not a wishbone in any useful fashion. At the same time I've changed my mind and it probably is not a great idea to characterize it as a semi trailing arm, because the camber is controlled entirely via the upper link. It isn't a Chapman strut because the shock does not provide the camber stiffness. It's actually a multilink, in my opinion. Which doesn't help much, as that is just a sin bin for any complex arrangement. Greglocock (talk) 03:03, 30 April 2016 (UTC)