triangulated vs parallel

can anyone tell me the pros and cons of these two 4 link setups or are they both equally good.

thanks

Edited: 9/16/2005 6:23:34 AM by ostncoln

Both styles of 4 link accomplish the same thing... very simply, they hold the rear axle in the vehicle. The function of a 4 link is to keep the rear axle in its proper place under the vehicle. The bottom 2 links keep the axle in place front to back. The upper 2 links keep the axle from rotating, keeping the pinion angle as constant as possible. On a triangulated 4 link the uppers bars are placed at an angle to the lowers. When connected securely to the axle and the frame they form a "triangle". This is what keeps the rear axle centered under the vehicle. On a parallel style, a "panhard bar" must be used. It runs horizontally across the vehicle connecting the axle to the frame, allowing only up and down movement. Although there are several theories as to which is "better", in the real world it comes down to available space and preference.

A parallel 4 link fits most trucks better because the fuel tank is usually right in front of the axle, inboard of the frame. A parallel is sometimes easier to install because the link bar frame mount is one piece instead of two... less time in placing and welding the upper bar mounts. But a parallel 4 link requires a panhard bar which adds slightly to the expense and can use up valuable space needed for the exhaust system. A panhard bar will also induce a small amount of side to side movement during suspension travel... not enough to feel but it may concern the customer who has an extremely tight tire to fender clearance. With a parallel 4 link you are locked into a sideframe link position... with a triangulated 4 link the lower links can be placed beside the frame or under the frame for clearance purposes.

Either system is very straightforward to install. You will spend more time with the tape measure than the saw or welder. All else being equal, for the absolute rookie, the parallel may be a bit easier to visualize and understand during installation. Triangulated 4 link (vs. parallel 4 link) PROS CONS No side to side movement at all... you can run tighter tire to fender clearance Less hardware to buy and install (no panhard bar) Allows flexibility in bar placement to avoid obstacles Angled upper bars can interfere with exhaust Angled upper bars can interfere with fuel tank on late model trucks 4 more attachment points to plot and install (parallel has bar mounts built together) Parallel 4 link (vs. triangulated 4 link) PROS CONS Slightly easier to visualize and install (bar mounts are built together) Can be installed beside framerail, inboard or outboard May allow more room for exhaust (no angled upper bars) Requires a panhard bar (extra cost and installation) Panhard bar will induce a slight amount of side to side movement during suspension travel... requires slightly more tire to fender clearance Panhard bar may interfere with exhaust Why should I put a 4 link under my car? What will a 4 link do better than a leafspring?

In a leafspring suspension, the leafs perform 2 functions. First, they hold the rear axle in the car. They prevent both forward and aft movement and minimize pinion angle change during suspension travel. Secondly, while they are doing this, they also support the load of the vehicle. For an OEM vehicle that has had thousands of hours of development time behind it, and that will operate within a predictable range of suspension travel, leafsprings do a very adequate job. The problem occurs when the operating envelope is changed... lower ride height, more horsepower, different weight distribution, maybe a trailer... it's called hotrodding! The leafsprings cannot be expected to perform as intended if the operating parameters are changed.

With a 4 link suspension, we have separated the function of locating the rear axle and supporting the vehicle, just as GM has done since 1958. We like the 4 link rear suspension because of its ability to properly locate the rear axle no matter how soft we want to make the spring. With a leafspring rear suspension, softening the spring rate can cause other problems such as side to side flex or axle wrap (when the axle tries to twist the leafs out of the vehicle). Just a few FAQs...

I have a straight axle under my '32 and am happy with the ride height and quality. Can I use an air suspension on the rear only?

ABSOLUTELY! We have several customers who have installed a 4 link and airsprings or ShockWaves

thank for all the info. it helps alot, i have a 2 link right now and it's a pile. i guess it does the job but, i dont like it

the parallel is badass if you are smarter than airride tech, i have a parallel 4 link with watts link on my f/s and it rides awesome, tows a trailer, and best of all there is no panhard bar to pull my rear end side to side.

hes right, parallel is better geometrically speaking, the bushings dont flex against each other and they move in their proprly designed path and with a watts the axle stays directly in the center. a triangulated will wear bushings much faster because the upper bushings are being used for side load, which they are not designed for and are also pulling away from each other whenever the axle is not at the center of ride height.
FYI
rear mounted bars dont always have pinion angle change just because they are mounted to the rear, thats stupid to even say thet. the pinion angle change is due to the difference in length of the upper and lower bars, or the placement of them. IF the rear mounted bars are all of the same length and the upper and lower bushings are directly verticle of each other the pinion angle will not change at all. but you will have the opposite driveline plunge as a forward mounted setup. on a forward mounted setup the driveline will go forward as you go above or below the height where the driveshaft and/or the 4 link bars are level.
on a reverse the driveline will be as far forward as it will ever go when its at the middle of its arc. the longer the bars are the less driveshaft plunge you will have.
the reason is that the arc is longer and therefore it takes way more movement to equal the same amount of forward or rearward driveline movement.
the optimal setup on a truck with a stock gas tank in front of the axle is a forward mounted 4 link or even a 3 link with a watts holding the axle in the center. however a triangulated when properly setup is very good as well and will give you very little problems. many peopl who install a triangulated will mount the angled bars too straight and it will allow the axle to move side to side as the bushings flex and give under more pressure than they can handle.

Michael, I think the ART statement is talking about running one set forward and the other back, not all in back or forward. As far as the bushings are concerned, superpivots setup perpendicular to the links instead of welding them parallel to the axle solves the problem of bushing wear. That changes the load back to push and pull to hold the triangle.

ostncoln bout summed it up

superpivots have very different charachtristics than a typical polyurethane bushing. but putting them in line with the axle doesnt eliminate side to side load flex on the bushings totally, it just keeps them from working against each other. there is still the axle trying to move side to side and that tries to flex the bushings but not as much and the wear isnt anywhere near as bad. most of the load is side to side and the bushings typical on a 4 link can handle some side load but not alot. but even a wishbone setup tries to twist the bushings some. this can be overcome by simply building the wishbone with very large bushings like the ones that Jason at SD sells. they overcompensate and therefore dont wear like a smaller one would. but dont think there are no side or twisting loads.