How Suspension Coils / Springs are made ? Raw materials & Design Explained

I’ve noticed a lot of colleges are running air shock’s instead of coilovers, this shocked me because in a fullsize vehicle air shocks tend to over heat easily at high speeds, thus loosing their valving and tending to raise the ride height, because of this there only really recommended for rockcrawlers.

what advantages are there to running an air shock over a coilover?

First off, they weigh nearly nothing. A fox float weighs 2.1 lbs, an evol ~4 lbs. In a lightweight vehicle application like Baja, they seem to dissipate heat quickly enough to be consistent over an endurance race.

Secondly, they can be fully adjusted with a mere hand pump and a few finger twists. This is partly laziness, in that we don’t have to go out and collect all of the right springs for every occasion, but it also allows us to adjust everything within two minutes. This is quite useful when ideal suspension settings are different for maneuverability and suspension courses. We can also adjust to driver preference on the endurance race.

Finally, in the case of fox shocks at least, we don’t need external bump stops. Evols progressively increase in pressure enough to prevent bottoming out anyways.

The real disadvantage of air shocks is the cost so far. As long as you have enough air in your Floats, bottoming out willn’t appear to be a problem. In many cases your throttle might stuck right before a jump causing us to get some massive air and bottomed out the front suspension so bad that it can snap the a-arm upward.

You can also opt for Polaris OE (Fox) shocks off of the RZR . They rock, just have to get softer springs for them. Also,

Raw Materials

Steel alloys are the most commonly used spring materials. The most popular alloys include high-carbon (such as the music wire used for guitar strings), oil-tempered low-carbon, chrome silicon, chrome vanadium, and stainless steel.

High strength steels for automotive applications like suspension coil springs and engine valve springs are alloyed with high amounts of silicon because it confers increased strength and hardness (solid solution hardening), higher sag resistance (resistance to load loss, resistance to stress relaxation) and temper resistance (resistance to softening during tempering and stress relieving). Contemporary spring steels are quenched and tempered to very high strength (1900-2150 MPa, 53-57 HRC, 560-640 HV).

Other metals that are sometimes used to make springs are beryllium copper alloy, phosphor bronze, and titanium. Rubber or urethane may be used for cylindrical, non-coil springs. Ceramic material has been developed for coiled springs in very high-temperature environments. One-directional glass fiber composite materials are being tested for possible use in springs.

The Manufacturing Process

The following research papers focuses on the manufacture of steel-alloy, coiled springs for BAJA Suspension


Design and Analysis of A Suspension Coil Spring For Automotive Vehicle

Optimum Design and Material Selection of Baja Vehicle

Baja Project ‐ Suspension Design Methodoly from BAJA Tutor

Designing an Independent Rear Suspension for Baja SAE Vehicle

SAE Mini-Baja – Suspension and Frame Design

Design of Helical Coil Suspension System by Combination of Conventional Steel and Composite Material




Scholarly Articles to Refer during Design phase

The design of various components though sometimes might seem too main stream, can be made interesting when one tries to incorporate result of recent research works in field of automobile, In particular, those related to a BAJA ATV.
When a team presents its buggy before the professionals, it should be able to reason out each single aspect of the car’s design. The strong backup for the reason is well bolstered by citing the research works which are published by SAE. Some of the good citations are discussed below.
(The papers shall not be available for free! This is just a guide which provides an easy way to look for SAE papers)
Validation of computer models:
1.Longitudinal performance of a BAJA SAE vehicle
Abstract gist: sensors and data acquisition system research, validation, fixation and installation in the vehicle, test and process of acquired data. From these steps, correlated data were acquired from magnitudes such as angular velocity in transmission shafts, global longitudinal acceleration and velocity, travel of break and throttle pedals and pressure inside of master cylinder.
2. Numerical and Experimental Analysis of Shafts – Applied to a Mini Baja Prototype Suspension:
Abstract gist: Piezoelectric accelerometers were used to measure dynamic response of the system. The numeric analysis was made using the transfer matrix method. By comparing the experimental results with those obtained by the transfer matrix method, the validity of this analytical approach is confirmed.
3. Validation of a Mathematical Model that Studies the Critical Steering Angle for a Lateral Rollover on a Baja SAE Vehicle:
Abstract gist: A comparative analysis presents similar values between the results obtained with the mathematical model, developed with the MATLAB software, and the results from the field tests, validating thus the purposed equations.

1.Structural Considerations of a Baja SAE Frame:
Abstract gist: A track is considered to have a sampling of obstacles and terrain that would be a good representative of what SAE Baja vehicles typically encounter. This work considers basic frame requirements, and explores several of these load cases using both experimental and numerical tools.
2. An Experimental Investigation on the Modal Characteristics of an Off-Road Competition Vehicle Chassis
Abstract gist: The goal of this experimental modal analysis is to validate a finite element model of the chassis, in order to develop a flexible multibody dynamic model of the complete vehicle. A preliminary finite element modal analysis of the test article was carried out in a free-free boundary condition. A random signal was used for FRFs acquisition. A multimode identification algorithm was used to acquire the system’s modal parameters

A Hybrid Transmission for SAE Mini Baja Vehicles:
Abstract gist: The hybrid transmission described in this paper provides a wider range of torque ratios by combining a CVT with a two-speed manual transmission. Included is a description of the major components, a derivation of the equations used to model the primary pulley in a simulation used to select the desired gear ratios.

Dynamic Experimental Analysis of a Mini-Baja Vehicle Front Suspension:
Abstract gist: An electric strain gages were bonded at the most critical points to measure the dynamic strains due to an impact load. The data obtained through an A/D converter with an instrumentation software, was used to evaluate the maximum loads acting on the suspension.

Thermoelectric Generator Applied to a Baja SAE Vehicle:
Abstract gist: The electrical energy produced in Seebeck Effect Cells, assembly in engine exhaust manifold, is conditioned and applied in vehicle batteries and supply energy consumption during vehicle operation. This action could increase the vehicle energy efficiency by the recovery the thermal energy dissipated.

Weight Reliability-Based Optimization of Framed Vehicles:
Abstract gist: A procedure for optimization considering discrete design variables is applied in weight optimization of a mini baja structure, with reliability-based design constrain. The lifetime estimation is based in time-domain approach, using “stress levels vs. Number of cycles” curves, the Palmgreen-Miner Rule to compute the cumulative damage and the Rainflow Method for cycles counting