<Note from Byron: I posted this in the Tech Section before I saw the topic for the month. It fits better here.>
Slick Spring Tricks.(modifying leaf spring suspension)
Author/s: Joel Mollis
Mods for Smooth-Riding Leaf Springs
Leaf springs: call 'em antiquated, call 'em old tech, call 'em unsophisticated; but also call 'em sturdy, functional, cost effective, and easy to modify. What makes a solid axle and leaf spring setup so popular is its inherent simplicity. Whereas a drive axle suspended with coil springs requires a complex multiple-link designed to locate the axlehousing and to allow for wheel travel, an axle using leaf springs as its springing medium is incredibly straightforward. The leaf spring packs properly locate the axlehousing in both a lateral and a fore-and-aft position; no additional linkage is necessary.
However, for all of their goodness, leaf springs have a dark side: innerleaf friction. To understand how friction is created by leaf springs, let's look at the basics of a leaf springs setup. A group of individual leaf springs bolted together us referred to as a leaf spring pack. As a pack is cycled (compressed and extended), the two ends of each individual leaf rub against the bottom of the leaf that is stacked on top. This occurs because the upward curvature of each leaf's ends are designed to support the leaf directly above it. As the spring pack is compressed, the curvature of these individual leaves flatten, and the leaf's ends rub against the bottom of the leaf it's supporting. All this metal-to-metal contact creates friction, and as the spring pack ages, rust and dirt gets between the leaves, creating additional friction. During actual use, inner-leaf friction actually, causes an increase in the spring rate, since it takes additional force to compress a rusty, sticky spring pack. Increased spring rate makes for an overly stiff ride and limits axle articulation during offroad romps.
The cure for inner-leaf friction is simple, straightforward, and can be performed by anyone with a few basic tools. The fix requires that each spring pack be disassembled, each individual leaf be smoothed, and anti-friction liners be installed between each leaf before the springs are reassembled into a smoothly functioning spring pack.
If you're ready for some slippery tech, let's have at it.
To select the proper material from which to make anti-friction spring liners, it's best to familiarize yourself with the some of the basic facts about plastic.
First, plastic names: UHMW, also known as polyethylene, is a plastic material with an Ultra High Molecular Weight. Polyethylene/UHMW is a durable, waxy, synthetic thermoplastic developed by German chemists during the early 1900s. Nylatron GS is a derivative of nylon. Nylon, a synthetic material invented by DuPont chemists in 1938, is made from petroleum, natural gas, oxygen, and water. Teflon is a Space Age, super-slippery material also known as PTFE, or polytetrafluoroethene, and is another product developed by DuPont during the early 1930s.
The thickness of the material used in anti-friction liners is also important. Although UHMW, Nylatron GS, and Teflon are available in various thicknesses, the best advice is to select liner material that is neither too thick nor too thin. Our source for all things plastic, Plastic Sales Southern offers a huge selection of anti-friction plastic material in every possible thickness, but the company suggests 0.030- to 0.060-inch-thick material for the sake of durability.
As for sizing, Plastic Sales Southern can supply any of the anti-friction material used in this story in two ways: by the foot or cut to a specific width. If you choose to purchase plastic material by the foot, you'll need to specify the length your springs require. Measure each leaf's a 1-foot-wide piece of plastic, then determine the length of material you'll need. If you prefer, call Plastic Sales Southern and give tell them the measurements; the material to length for the install.
1. Before the actual work begins, you'll need to decide which material is right for your truck's leaf springs. Our favorite material for spring liners is adhesive-backed UHMW. (A). If you prefer, UHMW is available without adhesive. (B). The dark material is Nylatron (C); the material on the right is super-slippery Teflon (D).
2. To get the smoothest action from a leaf spring pack, each individual leaf must be smooth and clean at the area where it rubs or comes into contact with the leaf directly above it. Carefully disassemble the spring pack, noting haw each individual leaf was originally installed. Using a small circular grinder with an 80- or 100-grit wheel, smooth the top side of each leaf, including the top of the leaf's edges.
3. With the leaves smoothed, take the time to spray on a few coats of epoxy paint. The coating will help delay the onset of rust and will provide a clean surface for the plastic spring inserts. Measure the width and the length of each leaf, then transfer the measurements to the plastic material.
4. Trim the plastic material to size with a razor blade or a pair of scissors, then place an insert an the leaf's top side. If you're using Teflon, non-adhesive-backed UHMW, or Nylatron, the insert will be held in place when the next leaf is stacked on top as part of the spring pack's assembly process. If you're using adhesive-backed UHMW, peel the backing material off and stick the plastic insert onto the leaf. Punch a hole through the plastic where the spring pack's center bolt passes and assemble the spring pack, alternating leaves and plastic inserts.
5. If the spring pack you're working on has spring clamps at its ends, you're in luck. If a spring pack doesn't have these clamps, non-adhesive-backed plastic inserts will tend to partially slip out from between the leaves after the spring pack is repeatedly cycled. For this reason, it's best to have a local spring rebuilder attach a loose-fitting clamp to both ends of a spring pack if you intend to install non-adhesive-backed inserts because the clamps will keep the inserts properly located. If you're installing UHMW with an adhesive backing, the insert will be held in place by the adhesive, so spring clamps aren't really required.
6. Select aftermarket spring packs are out. fitted with Teflon or nylon buttons at the leaves' ends. This Superlift Superide spring shows the insert and how it mounts to the leaf:. Small locating holes are punched into the leaf and accept the male studs on the plastic insert. This setup delivers smooth spring action and ensures that the insert will stay in place. National Spring can punch these holes in existing leaf springs and provide plastic inserts if you want to run this type of anti-friction insert.
1402 N. Magnolia Ave.
El Cajon, CA 92020
PLASTIC SALES SOUTHERN INC.
6490 Fleet St.
Los Angeles, CA 90040
(323) 728-8309 www.plastic-sales.com
211 Home Ln.
West Monroe, LA 71292
[ November 05, 2001: Message edited by: Sitting Bull ]