new first project

[Ron Sutton]

There are four common types of rear suspensions utilized in Pro-Touring cars today ... 3-link, Parallel 4-link, Triangulated 4-link & Torque Arm. Ladder bars should not be seriously considered for any corner carving car, as they go into instant bind with body roll & offer practically no articulation.

Note: The typical Torque Arm suspension is similar to a 3-link, using two lower trailing arms (or "control arms") ... but instead of the third link being on top (centered or offset) & pivoting ... it mounts solidly to the housing & extends quite far forward (closer to the center of the wheelbase) with it's 3rd pivot point.

Assuming each type of rear suspension is set-up correctly, rod ends spaced away from brackets properly with high misalignment bushings & clocked correctly ... the 3-link & Torque Arm suspensions allow the rear axle to articulate more (roll angle in relation to frame) than the 4-links.

They all will bind at some point of articulation. The Parallel 4-link allows the least articulation before bind ... the Triangulated 4-link allows a little more articulation before bind ... and the 3-link & Torque Arm offer quite a bit more articulation before bind ... all things being equal. It should be noted that DSE's Parallel 4-link (Quadralink) offers a little more articulation than other Parallel 4-links, due to their patented swivel link ends.

A triangulated 4-link is simple, and fairly common as a factory style rear suspension in many cars. It could be argued it will handle more torque under hard launches than 3-links, but if you were going to drag race it with slicks, you would want a Parallel 4-link, not a triangulated 4-link.

Torque Arm suspensions are also common as a factory style rear suspension in some cars. They are the simplest of the designs, allow a high degree of rear end articulation & can take high shock loads from hard launches. They can be made "a little" adjustable, but offer the least adjustability of the 4 designs, as far as controlling the front Instant Center, rise leverage & anti-squat. If designed well & installed as instructed, these make a great all around suspension for the person that doesn't want to tune much.

3-links are very common in road racing, especially in full body cars like GT1 & the Trans Am series, because they allow for the most articulation & can be highly adjustable & tunable for track conditions. You also see them on a lot on top AutoX racers.

3-links, Parallel 4-links & Triangulated 4-links can be made very adjustable if designed & installed with multiple or variable mounting points. But most "street kits" are sold with little or no adjustment to protect non-tuning novices from themselves. If you know set-ups or plan to learn, you may want to pick a system designed for adjustability. If not, pick a system designed for your application, install as directed & run it.

3-links can handle drag racing up to a point, but it wouldn't be my choice if the car was planned for 800+ hp, high rpm, clutch dropping, slick running, wheelie pulling launches ... as there are only 2 rod ends "pulling" to lift the whole car. 4-links can handle more launch load (like drag racing), because the force going through the rear end & rear suspension that "pulls" the top bar(s) is spread over 4 rod ends.

Parallel 4-links, 3-links & Torque Arm suspensions require a device to keep the rear end centered in the chassis, like a panhard bar or watts link. A triangulated 4-link does not require this, as the 2 links running at an angle keep the rear end in the location you put it. There are pros & cons both ways.



A suspension with a panhard bar or watts linkage ... "can" allow for easy roll center changes, if the mounting brackets allow for adjustment. (Most kits sold do not have adjustment capabilities) Again, decide if you want to "set it & forget it" (sorry Ron Popiel) or if you want a suspension that is tunable for optimum performance & varying track conditions.

So, for the best road racing, track car, or AutoX car, the 3-link has the advantage, with the Torque Arm suspension 2nd (for good articulation BUT not very adjustable), Triangulated 4-link 3rd & Parallel 4-link 4th.

For drag racing, the advantage goes to the Parallel 4-link, with the Torque Arm suspension 2nd (for handling launches BUT not very adjustable), Triangulated 4-link 3rd & the 3-link 4th.

For a "cruiser/driver" that will only occasionally see the track, with little or no tuning ... any of them will work fine ... but the Torque Arm suspension is best here & the triangulated 4-link 2nd ... which is why you commonly see these two suspensions in factory production cars. They both work fine in many hot rod & street performance applications. They are not better than the others, just simpler & effective.

Make sense?