Thread: Just wondering....

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Ok, picture a strut front car built for the digs and an occasional Saturday night with the boys....

If the lower A-Arm and the pivot point of the tie rods off the rack were at the same place (meaning the lower A-Arm length and Tie Rod length were equal) and the rack itself were centered at the exact center of the suspension travel (3" total travel for the sake of discussion) bump steer would not be a consideration, right??? But in this ideal setup, how would one make changes in the roll center with the lower arm being a single arm with a strut keeping it stable, much the same as a Strange or Lamb strut front suspension, but with corrected geometry????

Just a bit of early-winter, stuck in the shop engineering exercise.....not a project on the table....

Where A is the centerline of the strut...
B is a line drawn perpendicular to A....
C is the horizontal centerline of the lower control arm....
D is a line drawn from the intersection of A/B to the tire contact patch....
E is the centerline of the car left to right

Roll center can be changed by leaning the centerline of A to port or starboard. Leaning it inboard will raise the roll center and increase negative camber. Leaning it outboard will lower the roll center and decrease negative camber. It is said that lengthening or shortening the lower control arm will change the roll center also, but I fail to see how that would work without someone smarter than I am explaining it to me.

I can't put my hands on my copy of "Tune To Win" by Carroll Smith. It must be packed away in a box somewhere, but he could explain the relationship of the inner pivot points one to the other to prevent bumpsteer. This stuff is gettin' rusty on me....

To change the roll center, you either have to raise or lower the front, or the rear, or both of the car. You can also move the center of gravity height by raising or lowering it, by moving weight up or down, which will raise or lower the roll center. Or you could channel or raise the body.
Factory cars have a center of gravity height from 18 to 25 inches above the ground.
The further that the roll axis(center line of car front to back, which passes through roll centers) is from the CGH the more roll you get.


Pat

Richard, we must read the same books!!!! Same drawing I've been pondering... Thanks much for the help! I love the Strange strut front on a drag car, but IMO it's a bit light for the rigors of street use. I've got a pair of Camaro struts and a pair of Mustang struts I've been messing aroung with, both are easy to convert to coilovers and both have a multitude of brake options available....

Hemi, thanks for the input! As with all my "creations", this one has to be low and lean!!! Anything with over 4" of ground clearance gives me altitude sickness!!!!!