After trying to research online and carroll smith's "tune to win" i can't figure out the importance of having the lower control arms parallel with the ground - a common myth or fact with no real reason that's been spread around

they say, that if you go too low, it's bad to have your lower control arms at an angle

smith stated "Naturally, there is no law that states that unequal and parrallel links must be parallel to the ground at ride height" ....on our production cars, we use an unequal and non parallel links but i would assume that the above statement applies to our cars as well...except our upper control arms will naturally be at an upward angle

so i constructed the cutout model, and made it go through some motions but i can't figure out how it would effect anything:

at bump: both wheels go negative

at droop: both wheels go positive

at roll: outside wheel goes positive, inside wheel goes negative

I'm aware that since the upper control arm travels at a faster arc, it is the one that changes camber more drastically, but where does the lower control arm come into play?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by azian21485 &raquo;</TD></TR><TR><TD CLASS="quote">

I'm aware that since the upper control arm travels at a faster arc, it is the one that changes camber more drastically, but where does the lower control arm come into play?</TD></TR></TABLE>

Both it's length and static angle relative to groud plane (as reference) affects both the instantaneous roll center position in space and the migration of the roll center as the suspension moves.

 

It has to do with the location of the roll center. Traditionally, the ideal location for the roll center is at ground level. If the roll center is above ground, you get upward jacking forces, which raise the car as you go around a corner and cause more weight transfer. If it is below ground, then the distance between the CG and the roll center is greater than necessary and you get excess body roll. You also get downward jacking forces, which can be a problem if you're already running a very low ride height.

If the lower control arms are parallel to the ground, then you're guaranteed to have a roll center that is low and slightly above ground. In other words, near optimal.

All that being said, the amount of lowering that is even possible on our cars is not likely to cause the roll center to drop far enough to cause any problems.

 

awesome, thanks guys