WTF is a control arm? [Archive] - GrandAmGT.com Forum

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Marksman
01-04-2004, 06:54 PM
Sorry, I should know this, but I dont so I'm posting in the noob forum.
What is a control arm? Where is it located? What is it's purpose?
Pics are always good.
Thanks!

PS-Some have told me it's the sway bar, but I know what and where that is. Is control arm another name for the sway bar?

Jagey
01-04-2004, 07:26 PM
that's a good question, i want to know what the hell it is too

tenspeed
01-04-2004, 07:53 PM
It runs from the from the front wheel to the subframe of the car and holds the wheel in place.

In the old days cars had a upper and lower control arm. The steering knuckle was attached to it with ball joints.

In modern, light weight cars, the upper control arm has been replaced with the strut. All the is left is the lower control arm which has been shortened to the control arm. The sway bar is attached to the control arms.

jordanGT
01-09-2004, 06:45 PM
Originally posted by tenspeed
It runs from the from the front wheel to the subframe of the car and holds the wheel in place.

In the old days cars had a upper and lower control arm. The steering knuckle was attached to it with ball joints.

In modern, light weight cars, the upper control arm has been replaced with the strut. All the is left is the lower control arm which has been shortened to the control arm. The sway bar is attached to the control arms.

Pretty much...However; I'm going to disagree with those second paragraphs. In general, most unibody cars only have a lower control arm, and the strut attaches to the strut knuckle on bottom (which is attached to the control arm) and to the unibody structure (inner fender) at the top.
Non-unibody cars aren't set up that way at all, and not all new cars are unibody cars. Most light-weight cars are unibody, but full-size cars and most (probably all) trucks are still built on the stronger platform with a separate frame and body.
To further confuse the subject, some UNIBODY cars still use an upper and a lower control arm (most Honda cars still do). This way the strut doesn't have to turn, and less pressure is applied to the strut (this is why you can use traditional air cylinders in place of a Honda's struts, but if you put regular air cylinders in place of Grand Am struts, you're going to break the cylinders usually before you've even gone down the road a mile.

Here's a typical McPherson strut set-up, with only a lower control arm:
http://www.speedyautomotive.com/Conventional-McPherson-Stru.jpg

And here's a typical honda set-up, with an upper and a lower control arm.
http://www.honda.com.uy/service/suspension%20delantera.JPG

Marksman
01-09-2004, 08:05 PM
Thanks Jordan, that helped a lot!
Someone recently told me that my control arm bushings were shot so that's the main reason I asked. Guess I'll have to take a good look at that when I install my GR-2s
-Marksman