Overview and Explanations
In this article, I will explain what the different components are and how you should determine what best suits your application. All of the items discussed here are suspension-related. I will explain steering in a future article.
Link Suspension Joints
The most common suspension joints include Heim joints or rod ends, Johnny Joints and similar generic types, assorted rubber or poly joints from many brands, and spherical bearings or uniballs. There are others available, but these account for more than 99 percent of all real-world applications.
Johnny Joints
These were the original non-Heim joints used by four-wheel drives and were developed by John Curry at Curry Motorsports. Today, they have been copied extensively and considered a very generic type of suspension joint.
They are comfortable for day-to-day driving, but they have one major drawback, in my opinion. They require adjustment every five to ten thousand miles. If they are not adjusted when needed, they will wear very quickly, and the adjustment process itself can take several hours.
From a performance standpoint, they offer roughly seventy percent of the flexibility of a Heim joint, depending on the brand.
Rubber and Poly Joints
These joints are used in most factory applications and are designed to last one hundred thousand miles or more. However, in extreme off-road use, they are only forty to fifty percent as effective as Heim joints and will break down almost immediately.
Street ride quality is best when using these joints, but that comes at the cost of off-road performance.
Spherical Bearings
These are essentially the ball found at the end of a Heim joint, but used on their own. They become a built-in component of a suspension arm or tower and must be designed around.
When used correctly, they can be the best option available, but they are very expensive to implement. For that reason, they are most commonly used in racing applications.
Heim Joints / Rod Ends
These sit at the top of the ladder and are very commonly used, but not all Heim joints are created equal. The key difference is between one-piece and two-piece joints.
This comes down to simple physics. A joint can only be as strong as the materials containing it. Two-piece joints have significantly less material holding the uniball in place. If the materials are equal, such as heat-treated chromoly, the one-piece joint is unquestionably stronger simply due to material quantity.
If maximum strength is the goal, use a one-piece joint.
Maximum Flexibility
Rod ends used with misalignment spacers allow the greatest amount of movement. Some synthetic rubber-style joints may advertise more flexibility, but to achieve that movement, the joint must become pinched, which compresses the rubber to an extreme degree.
Once that point is reached, the rubber will tear. That is something you do not want. Adjustable cartridge joints also cannot achieve the same level of flexibility as a rod end because the body size limits movement and physically gets in the way.
Unreal Flexibility Claims
If a company claims its rod end can flex seventy-five degrees, look somewhere else. Anything over thirty-seven to forty degrees is physically impossible to use.
Just do a quick diagram in your head. If the axle tilts thirty degrees, where does the tire go? Right into the chassis or wheel well.
Leaf Spring
The Leaf Itself
There have been countless styles, thicknesses, and widths of leaf springs used over the years, but none of that really matters. What matters are the spring’s ratings and its intended use.
I recommend sticking with stock or modified factory springs or working with higher-quality spring builders and talking to them directly. They are more than willing to explain what they can do and how they can help. Even building your own bastard pack can be more effective than at rock crawling than an off the shelf Lift Spring.
If you want a simple and cost-effective installation, stick to the basics. Some of the most commonly used springs, and for good reason, are the sixty-three-inch Chevy springs found on Chevy three-quarter-ton trucks, with lower-rate versions used on half-ton trucks.
Jeep XJ (Cherokee) springs are also very popular for modifications. They are either very flexible or longer than stock and can be easily tuned by removing a leaf or two.
Desert racing has also inspired some excellent spring designs that work around SCORE rules restricting bypass shocks or multiple shocks. These setups work extremely well and do so at a fraction of the cost of a fully equipped link suspension.
Leaf Spring Attachment
This area is fairly basic, with a couple of important details. Most stock factory perches, plates, and hangers are too weak for extended use. Factory perches are notoriously short was well with very little spring actually contacting the perch, using a longer perch can dramatically reduce wheel hop and keep traction where you want it. Spring hangers in particular are commonly exposed to impacts, and the material thickness is simply not enough. One solid hit and they will collapse.
I only use spring hangers that are at least ¼” inch thick, and only when they are boxed to help prevent collapse. Perches and U-bolt plates are often thin, usually application-specific, and frequently discarded when changes are made to be replaced with stronger versions.
I recommend using ⅜” thick plates so they do not bend during installation or extreme use, and one-quarter-inch-thick perches to help prevent collapse when landing off a rock or a jump.
For U-bolts, I stick with ⅝” diameter in a 1511 factory-grade material. Always use tall nuts, as they were designed specifically for U-bolt applications. If someone offers you nylock nuts, walk away. They do not understand U-bolt dynamics.
Chassis Materials
Overview
I need to say up front that I am not a metallurgist. What I have learned over the years has been boiled down to the essentials you need to know before making expensive decisions when building an off-road vehicle.
Mild Steel
The term mild steel can be misleading. Mild does not mean weak. Mild steel is the most commonly used material in off-road chassis and components.
It is easy to form without compromising strength. Welding does not require special equipment and can be done with a MIG, TIG, stick, or gas welder using acetylene.
Stainless Steel
Stainless steel is an excellent choice when the correct grades are used, but it is very expensive. It can be welded using MIG, TIG, stick, or gas welding processes.
Chromoly Steel
Chromoly is a good choice for strength, but it can be brittle and may splinter on impact if used incorrectly. It does not require a special welder, although many builders prefer TIG welding.
It is significantly more expensive than mild steel, often costing three to four times as much.
Aluminum
Aluminium is also a very good material choice. However, long-term durability can be an issue when welded if it is not properly heat-treated. It works best for parts that are not subjected to extreme stress.
Bolts
The most commonly used bolts are grade five and grade eight, both typically zinc or Cadmium plated. The simplest way to think about it is that grade 5 performs better in shear, while grade 8 is better for strength applications. The actual difference between the two is relatively small.
There are many other bolt grades available. Some are cheaper, such as grade 2, which is essentially pot metal and should not be used. Others are far, far more expensive, and I will not get into those here.
If you feel the need to use the most expensive bolts available, you must be a big dollar guy and have no budget limitations, and probably are not reading this article anyway.
Summary
These are my thoughts, and they were challenging to put down in writing. I welcome your feedback, ideas, and disagreements.
I am 67 years old and have been involved in vehicle design, building, use, and repair since I was 15. If you spot a mistake or simply do not agree with something I have said, I want to hear it in the comments section.
Dan Fredrickson
Chairman and Founder
Ruffstuff Specialties