Slam Specialty(UPDATE: 7-21-08)

Hmm, okay I get it, but what does wheel arc mean, and the abbreviated IC mean?

Lol, and what would you recommend for a good spread for a 4-link to change very minimally during the range of travel?

Wheel arc is the arc that your axle travels around. Imagine your link bars as the radius of a circle. As it moves up and down it follows that track.

IC = Instant Center. Look it up. It will help you understand the spread between pivots, and why your upper and lower bars shouldn't be parallel.

I can't tell you a set dimension, because it varies with the length of the 4-link.

Mmk, so is there any sort of rule of thumb for this or is it just trial and error till you get it close to perfect?

I suppose I should ask this as well since it is related and pretty dumb to ask but sensible. When I weld the link tabs, how much slop should I have for the link ends in between the link brackets? Tight, or loose? Or just enough to let it pivot?

Its not trial and error in any way. Its really an exact measurement that relates to your vehicles COG. But it doesn't need to be too specific on a mini truck. Just tuned well enough to eliminate some wheel hop and properly apply the tires to the ground in acceleration or braking.

With bushings, they need to be tight. When you tighten the nut down you want the metal to squeeze the sleeve that is on the inside so that it pivots around that. I usually finish welding them with the tube insert bolted in place so they don't squeeze in too far from the heat.



I feel like the more I say the more questions I raise. I think you need to go read a suspension book. Get on Amazon and buy Chassis Engineering by Herb Adams, and read the rear suspension solid axle chapter about 3-4 times until it clicks. You shouldn't have any questions after that.

What about the heims?

Okay, so my link bars are 20" for the lowers and 24" for the uppers. I was thinking that the 4-link bars should be triangulated enough so that the link bars are equal the same length. Adjust the link ends for pinion change and what? Would I be good to go? Lol... lost, yes.

EDIT: Lol, sorry, I'll try not to go over the question quota tomorrow! Just trying to strive on doing this right! ya know?

Heims should also be tight in the tabs. But you should really run some misalignment spacers with those or you will damage the heim body. You can also work loose the jam nut or tighten it too much seizing the heim.

If you triangulate the uppers so that they match the length of the lowers they may not have enough triangulation. Its okay for them to be shorter than the lowers. I design all my link setups with shorter upper bars between the pivots viewed from the side. By a minimum of 1/2", usually more.


But seriously buy the book. It will answer your questions about suspension.

Ya, definitely need to indulge in that book. Weird how it seems alot of people who bag their truck don't even say anything on how complicated the 4-link is?

I never knew there was so much to it!

With the heims, all they gave me is washers to put on both sides of the heim, thats okay?

I'm not too sure I completely understand what you mean by the jam nut being too loose or seizing?

Well, most people just put the 4-link in the easiest place to make it work. Thats commonly what I see. And then they just accept the way it works, good or bad. And then defend their choice to the death. Its the mini trucking way.

Personally I would say no to the washers, but other people have run the FBI links that way for years without many issues other than heims wearing out. Which is where that binding comes in I mentioned, which can be alleviated with proper spacers. I guess I just do things differently than the average Joe. Personally I wouldn't use an FBI link in the first place, but thats just me.

Lol, I get what ya mean! I think its more of just being stubborn and not wanting to really understand it all and do it right...

You sure do have it down to a science, Seth!

Alright, well, if I can't do the washers, what should I do to help them? I need it in pretty much lamens terms cause I have no clue what a misalignment spacer is, lol!

Personally, I would go a diff. route on the 4-link now, but I'd rather not waste any more money so long as I will still be able to run my setup without major issues.

I understand the money thing. And the FBI 4-link will do its job just fine.

You can get misalignments from Ballistic Fab.


Looks like this:


Helps the rod end body move more freely before it binds.