In The Past Two Decades Link-style suspensions have gone from a desert-race exclusive to something being built in garages and barns across the nation-and for good reason. Link suspensions separate the jobs so that each component of the suspension can do its part exclusively and thus better. For example, the springs on a link suspension don't locate the axle like a leaf-sprung suspension, so axlewrap is eliminated. Since the links move the axles in an arc that can follow the driveshaft, U-joint bind is often reduced. Approach and departure angles can also be increased since the links do not stick out past the axletubes.
Where do you start when it comes to building the links themselves? The market is flush with different types of rod ends, flexy joints, and bushings to go on either end of the suspension links. We've seen links made of everything from aluminum to square tube, but which is right for you? Here is the lowdown on the latest link-builder parts for your perusal.
These nonrebuildable rod ends are also referred to as Heim joints. The three major ends that show up on 4x4s are made by FK, Aurora, and QA1. They consist of a swiveling ball inside a forged outer body and come as either a three-piece (FK, Aurora), where the ball and race is swagged into the body; or as a two-piece, where the rod end is inserted in the body and rotated and then a plastic filler is injected around the spherical end (QA1). Some rod ends have a Teflon liner around the sphere for longevity and silent movement. Rod ends are described by the diameter of the shank and the diameter of the sphere bore, such that the upper joints are 1.25 by 1 inch. In order to get additional angle out of the rod end, misalignment spacers are used (arrow). These allow the rod end to twist to a greater degree than if the tabs were right against the sphere. The nuts on the shank of the joints are known as jam nuts. These are tightened against the end of the link to keep the link from unscrewing. Also note the shoulder, or step, around the sphere bore on the smaller rod ends in the lower center and right of the photo. These are for additional misalignment and are often used on steering links.
Suspension links have a flexible...
Suspension links have a flexible end, whether it's a rod end (aka Heim joint), bushing, rebuildable spherical joint, or some other unit that allows the link to move while locating the axle and transmitting forward motion from the driven axle to the chassis.
Many suspension links have...
Many suspension links have simple poly bushings with inner and outer steel sleeves. The outer sleeve is attached to the tube of the link in some way and the inner sleeve is where a bolt runs through the bushing and chassis or axle mounting tabs. Using bushings is good when you have links that need to keep from twisting, such as when the shocks are mounted to the links instead of to the axlehousing. The upper bushing assembly is from Ballistic Fabrication and has a welded shank, while the lower bushings are from Poly Performance and can be assembled and welded by the suspension builder.
Rebuildable joints are usually...
Rebuildable joints are usually less expensive and often use a poly-style inner bushing with a spherical ball inside that can flex and rotate. In the front is a disassembled Currie Johnny Joint and an assembled Johnny Joint with a forged shank and housing. These were some of the original rebuildable joints and we sourced them through Poly Performance. The disassembled joint in the center top of the photo is a Rubicon Express Super Flex joint that uses a threaded insert allowing it to be tightened for adjustment and then a small set screw to lock the insert in place. In the upper left is the Ultra Duty Joint from Ballistic, very similar to the Rubicon Express joint, but shown with a threaded rod end. In the upper left- and righthand corners are the tools used to tighten these threaded joints. In the lower left is the massive Evo Heim joint from Evolution Machine. This is right on the edge between being a rebuildable bushing joint (it has a Delrin insert) and being a solid Heim. Evolution claims strength to more than 100,000 pounds of pressure.
You can attach a threaded...
You can attach a threaded rod insert into the rod end as shown in the bushing photo, or you can tap the actual tubing of the link, or you can weld in a threaded bung. There are many different makes and models of threaded bungs-from (right to left) hex and nonhex bungs from Spidertrax, a righthand threaded bung from Poly Performance (the small groove cut in the bung denotes righthand thread), and small righthand, large lefthand, and square righthand bungs from Ballistic Fabrication. Having a left- and a righthand threaded bung and rod end at either end of the link allows you to adjust the length of the link without removing it from the vehicle. However, some builders find that having the same thread at each end reduces the chance of the links loosening and getting longer or shorter by accident.
For any suspension link we...
For any suspension link we recommend nothing less than a Grade 8 bolt (right) and if you really want a strong bolt look into the F9-11 bolts from Foremost Threaded Products. F9-11 bolts are 20 percent stronger than most Grade 8 bolts and have a 180,000-psi minimum yield. And unlike many fasteners that you find at local hardware stores, these are also made in America.
The links themselves can be...
The links themselves can be made from a plethora of materials. Spidertrax and Poly Performance are both offering heat-treated chromoly links made to order. Many rockcrawlers build their links out of 7075 T6 solid aluminum for a strong, lightweight link. We have seen a lot of rigs also running simple DOM tubing (check out our suspension story elsewhere in this issue with examples of different link suspensions), but the wall thickness should increase if you go with DOM instead of chromoly. A 1/4-inch-wall tube with a 1/8-inch-wall tube sleeved over it seems to be a pretty common DOM link for smaller vehicles. As you get up into fullsize truck weight, you'll want to start looking into thicker wall material and/or exotic material like chromoly.