LCA length VS UCA length

[xcm]

So im currently in the build stage of my front 3/4 link, and ive ran into a snag in the planning stage. What i was planning on doing, was build a crossmember with mounts on it, in a similar configuration to the RK 3link, but i have a set of full traction arms sitting around, so i figure use em right? well, the FT lowers are about 4" longer than the uppers, which means my crossmember has to reach out an extra 4" to mount the uppers...

I compared lengths between the RK 3 link, and the FT 4link, and it seems the rk's are closer to a similar length (dont have them off the vehicle to measure), while the ft arms have the 4" differance...


so, in a 2wd application, on a excel-less build, what would you guys recommend? the FT arms arent mine anyway, so they were gonna be for mock up only. So i dont mind starting from scratch.

 

[FatCity Ryan]

Try drawing the suspention cycle on the garage floor. Check your pinion angles and caster change. Then decide wich one you like best.

 

[Baja_XJ]

What I done when building the crawler was I got a sheet of 1/2 plywood, a bunch of 1/2 wood dowels, and a 1/4 wood dowel. Cut a strip of the plywood into a piece about 1x6 to represent the axle and use the 1/2 dowels to represent your links, and use the 1/4 to represent your bolts and just scale everything by 1/2 or 1/3 or 1/4 etc and drill holes on the plywood and you can test your lengths and separation prior to building it. Much like Ryan said but I found this to be a much more controlled test

 

[Goatman]

I do what Ryan said, draw it on the garage floor with chalk. Then I just use string to duplicate the arm movements and create the arc of movement of the axle and see what the changes look like. Bottom line, in a 2wd it won't matter. Also, 4" difference in length in a roughly 36" arm won't matter much either. The main issue is pinion rotation due to the different arcs of movement of the lower and upper arm contact points on the axle. The effects of a shorter upper arm can be minimized or eliminated by the upper arm angle being flatter, or even slightly up at ride height, so the arc of movement is close to the lower arm.