I'm starting to setup my 4 link and figure out lengths, locations, etc.. I have all the brackets, hardware, and materials I need. The issue I'm running into is that the F100 frame is pretty narrow which prevents installation of a decent length upper link while maintaining safe minimum triangulation angles (~30* each link from truck centerline). The other part of this is that I can't install the rear mounts for the upper links that high up on the 9" housing without making the upper link start to slope downward towards the frame since my forward bracket are level with the frame. This creates a very short link from side of the housing to where my frame is boxed in. I did a quick sketch to help visualize, but anyone that has built these I'm sure understands what I am talking about. When all said and done, from rod end eyehole to bushing eyehold, my upper link length would only be about 12-13"... This seems really short... Keeping with general geometry guidelines, this means my lower link would also only be about 16" long.
Well what I'm doing is not much different than the MANY "universal" triangulated 4 link kits out there, except that I am using good sized heims, beefier brackets, etc that I have selected. Much better than the many 7/8" tube with bushing on both end basic kits that get slapped on tons of builds without a lot of thought. Realistically, I shouldn't have much suspension travel at all with my coilovers, so I'm wondering if on a lowered truck with fairly high spring rate if it is even an issue. Just trying to think through everything before I even begin tacking anything in. Thanks for the reply!
My other option is to mount the upper link forward mount all the way inside the frame against the C-channel back side, then just box around it.. Not the best method, but this would gain me a couple inches in link length easily...
For anyone that runs into this in the future with the same issue/questions:
Spoke with a couple different chassis builders and they both pretty much summed up that nothing is ever perfect with these setups in limited space, and you'll have to compromise somewhere
Overall,
-The 30* (60* total between links) angle is great and should limit pretty much all movement
-The 12-13" length uppers are a bit short, but not really another option. Pay attention to pinion angle. If not much suspension travel, pinion angle change will be minimal. Also, the Fox bodies had a very very short upper and many have modified those rear ends a bit and those have performed well setup properly.
-Following the 70% rule for the uppers (upper length 70% of the lower length from section view) and setting them up pretty much parallel from section view will yield satisfactory results all around for a street truck and general performance all around.
See if you can download this four link calculator. It has been through a few revisions and the guy that came up with it used to host it on a site years ago but it is long gone. He posted on Pirate4x4.com and there are several broken links on there but this one is from one of the members (patooyee) who is continuing to host the file.
Aerocoupe wrote:See if you can download this four link calculator. It has been through a few revisions and the guy that came up with it used to host it on a site years ago but it is long gone. He posted on Pirate4x4.com and there are several broken links on there but this one is from one of the members (patooyee) who is continuing to host the file.
Maybe it will help you see the math and better understand how the suspension will move and allow you to come up with the best arm lengths.
Thanks! I actually found this elsewhere, but have only been able to get it to work through the link you just posted. Been messing around with it and think I have found some geometry that will work well enough through 3+" of travel, which is much more than I would ever anticipate with my coilovers.
