Brainstorming About Linked Suspensions
My name is Dale Hardin and I work at a Four Wheel Drive Shop in Florida. I have a few questions, and I am hoping you may be able to point me in the right direction. I am looking to build a four-link suspension on a truck of mine, but the problem is I can't find any info on four-link suspensions anywhere.
Dale Hardin, Florida
I am an avid off-roader and have always been a do-it-myselfer. I have an old Chevy that is my test truck for everything I do. I was wondering if you could tell me how to build and lay-out a four- or three-link rear suspension. Would you be able to tell me of a site that would show me how and where to take the measurements from? I was also wondering if it is possible to do it to the frontend with a solid front axle. Will you be able to go pretty fast and still be able to do some small jumping? My last question: Do you know of a site that I could learn more about a dry sump oil system, and what parts are involved in putting a dry sump system in a vehicle?
Bryan Grenewald, via e-mail
I'm currently in Iraq as a grunt, but I'm looking forward to coming home and modifying my '03 Chevy S-10 ZR2. I have a 6-inch Superlift suspension lift kit on it, and I'm running 33x12.5x15 Interco TSL radials. I'm looking to put 36x12.5x15s on it. I'm thinking of a solid front axle for it. I'm not really sure what to do; I need some expert help.
Lcpl. Justin Howard, Iraq (Hometown: Great Valley, New York)
Since all three of you asked similar questions, we'll try a blanket response. Yes, it's absolutely possible to build and install a linked suspension for the front or rear of an off-road truck. As to the question of whether or not a solid front axle can do high-speed work and catch air, consider the XJ Jeep Cherokee and the '66-'77 Ford Bronco, both of which use a linked front suspension with a solid front axle, and have been perennial favorites for high-speed work and off-road racing. The XJ uses a four-link, while the Bronco uses radius arms to connect the framerails to the front axle.
The tricky part of the process is adapting a linked suspension to a truck that originally had IFS or leaf springs. You'll need to do a lot of measuring; the links must be mounted correctly and consistently or you'll get all sorts of scary handling and wacky suspension action. Your best bet is to do a lot of research before you lay a finger to your truck. We'd suggest "Chassis Engineering" by Herb Adams as a great place to start. Herb's book is set in the world of pavement racing, but the engineering principles discussed by Adams can be adapted and configured to the dirt world we live in. Another factor in the way your link suspension is designed is your intended use. Prerunners and desert trucks have very different suspension requirements compared with trail rigs and hard-core rockcrawling buggies. Just one example: Rock buggies and trail rigs need the maximum ground clearance possible, while prerunners and desert trucks tend to hang their suspension links lower in order to get a lower center of gravity and better high-speed handling. We'd also find off-roaders with linked trucks in your area that are into the type of off-roading you're into, and talk to them about their suspension setups. To help with your research, we'd also suggest checking out a four-link calculator created by a friend of ours who is a degreed mechanical engineer. The calculator is not a complete designing tool for a specific vehicle, but can help you figure out critical elements of your design such as roll center and anti-squat. There is a thread about this calculator at www.pirate4x4.com/ forum/showthread.php?t=204893.
One oft-overlooked aspect of a linked suspension is an antisway bar. Leaf springs have an inherent resistance to twisting that coil springs and coilovers do not. An antisway bar is needed to control body roll and ensure stable handling. Three sources of antisway bars are: Currie Enterprises [(714) 528-6957, www.currieenterprises.com)]; Speedway Engineering [(818) 362-5865, www. 1speedway.com)]; and Curt LeDuc's Cal Pre-Fun [(951) 845-8820].