A arm leangths?

[miller]

Hey those of you with custom double a-arm suspension. What lengths are your arms? Im assuming most of you are using un-equal length. I was planning on having a fairly long lower arm and a upper arm thats about 20% of the length of the lower? Dont have exact figures yet but I will as I get my wood mock chassis put togeather. Thanks.

[ricola]

20%?! That's way too short!

As a rule of thumb the top arm would be about 2/3 the length of the lower arm. All this will obviously change depending on designed suspension travel and ride height arm angles etc etc

Rich

[miller]

Ricola what are you arm measurements? Oh and I messed up on the 20%, I meant 80% but said it backwards. Basically it seems a long rod will lessen camber change and make the suspension more predictable. And tilting the upper link down toward the center of the car will result in more negative camber in bump and less positive camber on the laden wheel, decreasing the ammount of chassis movement before camber control is lost. SO pretty much im trying to design around that and the only unknown is arm leangth cause that seems to decide how my camber change is gonna work out.

[ricola]

Off the top of my head I can't remember. I was restricted as I didn't want to make any modifications to the pan so I made the lower arm as long as I could and sized the top arm according to calculations I did...

Rich

[miller]

how did you do that calculations? Did you have some suspension program? It seems from my reading that camber control is important but secondary to roll center control and keeping the front and rear roll centers somewhat equal even though that will probably never happen.