Front suspension geometry

[volkdent]

I don't get it myself. I asked about it before, but havn't heard what the difference is. My M3 has them towards the front, a bunch of other cars to the rear. Part of it may just be packaging, where the steering rack will fit and all that.

Jason

[tommi_nylund]

Answer for your and my question is Ackermann-steering.

But I´m not sure how it make the effect of oversteer or understeer... It is somehow related to angles how much front wheels are turned..... For example if you turn right all you´ve got your left front wheel turns let´s say 20 degrees and your right wheel 30 degrees. There is secret of that. BUT this will only happen (if I´m not completely wrong) when you have angled steering arms, not ones which are pointing straight front or back. (like 944´s are pointing straight front)

Cars which have straight (parallel) steering arms does not have Ackermann steering, because both wheels are turned same angles.

Then when you have angled steering arms, you can draw a line from lower ball-joint via steering-rod end so long that it will reach the car´s centerline. Then you draw same line from another side and then you look where does these lines cut. Is it front or back of the rear axle center or just at center of that. Then you´ll have 'More', 'Less' or 'True' Ackermann.

I don´t know how these make effect. I´ve found no information from the web and no one haven´t explain me this thing either.

For example 944 have parallel steering arms pointing front. 914 / 911 have angled steering arms pointing back. Why is that???

[yetibone]

I think the placement of the steering arms on the spindles has to do with placement of components due to space available. Like Jason said, it's about packaging components together.

A 914 and 911 could feasibly mount it's steering aparatus either in front of, or behind the front wheel axis' because no other nessecary components occupy that area. Standard Beetles are "rear steered", or have steering arms, and steering aparatus behind the front wheel axis' as well, but only because the design warranted such an application. The steering box convieniently mounted on the upper torsion tube, and unequal length tie rods connected a common Pittman arm to rear facing steering arms. When designed, I think that Supers could have gone either way. I believe it could'ive been "rear steered" instead of "front steered" and the framehead would'nt look much different, but don't know if it would'ive made much difference in what was supposed to be such a humble, and conservative automobile.

[PJL54Oval]

On the subject of Ackerman angle. To find the corect angle for the steering arms, you draw a line throught the front ball joint to the center of the rear axle centerline. The tie rod should fall somewhere on that line. For front steer vehicle, just mirror the angle forward of the front axle centerline.

[Steve C]

Hi

Something to be aware if your running excesive castor, the same forces that keep the steering wheel straight when going forward will work against you if you ever spin your car and find yourself going backwards fast, the steering will wip itself into a full lock condition.

Steve