If you have further questions or would like add a topic to the list please email us. I tell all my students that there is no such thing as a stupid question. I would rather answer your question and keep your attention as a student then lose you to confusion that can easily be remedied.
I dedicate this section of the website to those searching to expand their horizons. There are so few sources of information on off road suspension, Chassis design, and setup. I want to thank all those who have contributed and I would like to extend this knowledge to those willing to learn. Please read on.
List of technical terms
What is IRS and what are the benefits?
IRS stands for Independent Rear Suspension. Independent suspension is a type of vehicle suspension system where each wheel can react to differences in the road surface without influencing the other three. IRS is used by fastest high performance Racing Vehicle. From F1 to Baja 1000 the fastest vehicles in the world on or off road have independent suspension.
What is un-sprung mass and why does it matter?
Un-sprung mass is the mass of all moving parts of your suspension. This includes everything from the wheels, tires, hubs, axles, a-arms, and shocks. If it moves when you hit a bump it is un-sprung mass. It is very important to keep your un-sprung mass to a minimum. The faster your suspension can react to bumps the faster you can get your tires on the ground and accelerate.
What does an anti roll bar do and how can it benefit me?
An anti-roll bar is a combination of a torsional spring and linkages that connect the left moving suspension members to the right moving suspension members and effectively limits the body roll in a vehicle. Anti-roll bars are used in all street automobiles, road race cars, and off road race cars today. A correctly configured anti-roll bar will properly distribute the load on each corner of the vehicle in order to achieve the maximum traction and cornering speed. An anti-roll bar can also be used to adjust the steering characteristics of a vehicle.
What influences my vehicle's body roll and what can I do to fix it?
Body roll is a phenomenon that occurs when you’re cornering forces act at the center of gravity of the vehicle leaning the vehicle to the outside of the turn. The magnitude of body roll is governed by the distance from your suspension’s roll center to your CG. The distance between your vehicles roll center and the center of gravity is the length of the fulcrum. If your roll center is close to your center of gravity you will experience less body roll then if it is a long distance. To limit your body roll you can use stiff springs to counteract the body roll but this may offer a stiff ride. The best way to limit your body roll is by using an anti-roll bar.
What do my Shock adjustments do and how do I set my shocks up?
Most adjustable shocks have a compression adjuster at the top of the shock body and a rebound adjustment at the bottom. Some higher technology shocks also have a high speed compression adjustment.
The compression adjustments fine tunes the shock’s ability to resist compression. The low speed compression adjusts slow compression movements such as lateral and longitudinal load transfer, and the rate of body roll. High speed compression adjusts the resistance to big bumps woops and jumps.
The rebound adjustment resists the force of the spring as the suspension relaxes after being compressed.
What is the difference between using an anti roll bar to limit your body roll using shock crossovers and compression settings?
An anti roll bar uses the extended suspension member to add spring rate to the compressed suspension member effectively limiting roll and squatting the vehicle. The rider will feel more stability and a squat coming off the corner. Spring crossovers add spring rate at a certain ride height so the spring stack exerts more force to the compressed suspension members but no squat is seen and proper weight distribution to each of the four wheels isn’t seen. If you adjust your roll using the low speed compression adjustment on your shocks you can adjust the rate at which the vehicle will roll but ultimately in long corners the vehicle will roll to the same roll angle and roll isn’t limited.
What materials are good and what do they mean to the racer?
Most race products are made with materials that have a high strength to weight ratio. It is beneficial to keep the weight of your vehicle down as much as possible because mass opposes acceleration. Approved air craft grade materials are the best solution for the racer. For aluminum the grades most widely used are 6061 T6, 2024 T4, and 7075 T6. For steel components Chrome molly is used. Chrome molly comes in several grades such as 4140, 4130, 4340, and 4340 Modified 300 also known as 300M. For most aluminum components 6061 is used having a strength rating around 35000psi. Next is 2024 having a rating of about 45000 psi and the strongest is 7075 having a strength rating of about 75000 psi. Your extreme strength and wear components are made from 7075. High grade sprockets and some engine connecting rods are made from 7075.
The various grades of Chrome molly also have their own strength characteristics and properties. All of the grades listed are heat treatable and should be heat treated to gain the most benefit possible out of your material. The main differenced between the various grades of chrome molly are the carbon content, chromium content, and molybdenum content.
Why is my chrome molly frame TIG welded and what does this do for me?
Chrome molly tubing should only be TIG welded. This is because chrome molly is prone to stress cracking in the heat affected region right next to the weld. MIG welding or stick welding will over heat the welded joint and make for a weaker weld. TIG welding is also a much cleaner weld and it is easier to control the pitting and porosity of the weld. It is also very important to flame stress relieve your weld joints after welding to relax the metal and reduce the change of cracking.
How much power do I lose through my CV joints?
Power loss through CV joints varies slightly by the misalignment angle. If your CV joint and axle are aligned under power there is no loss at all. At max misalignment about 1% losses can be seen. Power loss with the CV joints is lost by friction. All CV’s have a break in period of about 300 miles. In the beginning of the life of the CV’s they will heat up and be hot to the touch. This is where your lost power goes. As the CV’s get broken in they heat up less and become more efficient.
