a-arm : a type of suspension which includes an upper and lower control arm, connected to a spindle with balljoints or uniballs. Either a coil spring or torsion bar is used for load bearing. This suspension is among the most common on production vehicles today, due to its road handling characteristics. Unlike beam or straight axle suspension, a-arms have very little camber change throughout its cycle. Here is a picture explaining the basic components of a-arm suspension.
ackerman steering : wheels steered around separate axes must have the inside wheel turn at a sharper angle than the outside wheel. This is due to the the inside wheel moving through a smaller arc. The difference between the inside and outside steering angles progressively increases as the wheels are turned more sharply (higher lock angles). At the low steering angles typical of highway speeds, differential steering is relatively unimportant.
air in : v. The entrance (or “in”) of a ditch, vado or other road feature that provides an opportunity for an air-op. 2) v. The process for restoring a tire to a functional, round shape.
air-op : n. over the last hill and it's safe to jump.
air out : 1) v. to drive an off-road vehicle over a jump causing it to lose contact with the road surface. 2) adj. The exit (or “out”) of a ditch, vado or other road feature that provides an opportunity for an air-op. 3) v. The process by which a tire becomes non-functional.
airbump : hydraulic bumpstops that are pressurized with nitrogen to aid in hard bottom-outs. Usually 2 or 2.5" in diameter and 4" in length, these cushion hits much better than the traditional bumpstop. Here is a picture of a standard airbump.
a la mangera : Method of dispensing gasoline from drums using a length of hose and siphon techniques.
alloy : a metal formed by a mixture of two or more different metals.
annealing : the process of putting material in its softest condition for further processing. This is normally done by heating material to a certain temperature, then cooling it under controlled conditions.
anti squat : rear suspension design that resists squatting forces. This causes the rear end to stay relatively level under acceleration. Here is a picture showing how anti-squat is created.
axle : shafts that engage with the differential that turns the wheels to propel the vehicle.
axle wrap : caused by torque of the rear wheels twisting the leaf springs into a sort of "S" shape. This is unwanted suspension movement that allows the pinion angle to change.The springs twist and untwist rapidly, causing the rear to hop under power. Spring-over axle leaf setups are more prone to axle wrap than spring-under configurations. Shock placement, such as one shock facing forward and one facing backwords, is done to reduce wrap. Axle wrap is also increased by lift blocks. Here is a simple diagram showing the leaf twisting under axle wrap.
balljoint : pivoting joint used to join a-arms to spindles, or beams to spindles. A stronger alternative to a-arm balljoints are uniballs, which most race teams run instead. Here is a picture of a balljoint pressed into an upper a-arm.
beadlock wheels : center the tire between a shoulder machined on the rim, and an outer ring attached to the rim with grade 8 bolts. Because the tires are held on by the outer ring, and not by the air pressure on the bead of the tire, beadlocked wheels can be ran at any psi. These wheels are beneficial off road because they keep the tire on the wheel over rough terrain (rocks and holes) at high rates of speed (well in excess of 100mph), and allow for the tire to be safely aired down on sand.
bed stiffeners :tubes used to brace the bed on a truck without a tailgate. These run from the upper corner of a bedside down to the bottom of the bed, which triangulates it and keeps the bed from tweaking.
bending moment : if a force acts in such a way that it may cause a material to bend, then the force multiplied by the perpendicular distance to the axis about which the bending could take place is called the bending moment. The formula is identical to that used to calculate a torque.
billet : an item created from a solid block. Usually machined pieces, not necessarily aluminum. Here is a picture of a billet upper control arm from the Herbst truggy. Also see CNC.
BITD : Best In The Desert racing organization. Race information, basic class rules, and more can be found here.
bogie : n. officer of the law.
brakelights : n. radio call that indicates lead vehicle has encountered a hazard that warrants a rapid reduction of vehicle velocity.
bumpsteer : toe change during the supsension cycle which can cause the vehicle to dart side to side. This is caused by the steering linkage moving in a different arc than the suspension.
bumpstop : rubber, polyurethane, or hydraulic stop used to cushion the last stage of suspension compression.These, along with limiting straps, can be used to correctly limit a suspension and prevent damage to shocks and suspension pivots. Here is a picture of a standard urethane bumpstop.
bypass shock : similar to a standard shock absorber, in that they are velocity-sensitive, but are also position-sensitive. Bypass shocks have a valving system located at the head of the shock piston as well as external metering valves that allow for the adjustment of rebound and compression of the shock. As the piston is compressed into the body of the absorber, oil is pushed through the external bypass tubes and looped back underneath the head of the piston. Under rebound, the oil does the same thing, only in reverse. This process is dictated at an adjustable rate defined by the external check valves. Depending on make and model, some bypass shocks can offer multiple tubes, typically one for rebound and one for compression. Some of which have multiple, adjustable check valves to control the metering of compression and the metering of rebound.These are commonly available with 2, 3, or 4 tube bypasses.
CAD : Computer Aided Design. General term referring to applications and the method to design things using your computer. The ability of a computer to calculate fast, and show the results in graphical form, is utilized to create software packages that enable designers to study the properties of a particular design quickly and accurately. The final design is often combined with CAM (computer aided manufacturing), written as CAD-CAM. A popular CAD program is AutoCAD.
camber : The inward or outward tilt of the tire/wheel assembly. This angle is measured from a true vertical line, perpendicular to the ground. A tire/wheel assembly that is tilted outward at the top is considered to have Positive camber. While a tire/wheel assembly tilted inward at the top, displays Negative camber. For a zero setting, the tire/wheel assembly is in the exact vertical position or perpendicular to the ground. Here is a diagram explaining different camber settings.
effects of positive camber : results in a dynamic loading that allows the tire to run relatively flat against the road surface. Positive camber also directs the weight and shock load of the vehicle on the larger inner wheel bearing and inboard portion of the spindle rather than the outboard bearing. Positive camber in moderation results in longer bearing life, less likely sudden load failure, and as a side benefit, easier steering. Excessive positive camber wears the outside of the tire and can cause wear to suspension parts such as wheel bearings and spindles.
effects of negative camber : negative camber can be used to improve the handling of a vehicle. A setting of 1/2° negative on both sides of a street car will improve cornering without affecting tire life greatly. This negative setting compensates for the slight positive camber change of the outside tire due to vehicle roll, thereby allowing a flatter tire contact patch during cornering. Excessive negative camber wears the inside of the tire and similar to positive camber, it can cause wear and stress on suspension parts.
cantilever : A beam or tube that extends outward, supported at one end only, and varying in thickness. A cantilever has zero bending moment at the unattached, thinner, end, and a maximum at the attached thicker end. (see picture)
caster : The forward or rearward tilt of the projected steering axis from true vertical, as viewed from the side. This line is formed by extending a line through the upper and lower steering knuckle pivot points. For vehicles with front control arms, visualize the line extending through the upper and lower ball joints. Caster is always viewed from the side of the vehicle. When the upper pivot point is rearward of the lower pivot point, caster is positive. If the upper pivot is forward of the lower pivot point, caster is negative. When the two points are straight up and down from each other, the caster is zero. Caster is not a normal tire wearing angle and is used as a directional control for stability and steering returnability. Caster effect is necessary so that the load of the vehicle is "carried" through the steering axis line formed on the upper and lower pivot points. Here is a diagram explaining different caster settings.
effects of positive caster : positive caster promotes directional stability, however, excessive positive caster can cause two problems. The first is that excessive caster will cause a high level of road shock to be transmitted to the driver when the vehicle hits a bump, etc. The second problem is that a tire/wheel assembly with positive caster has a tendency to toe inward when the vehicle is being driven. If one side has more positive caster than the other, this causes it to toe inward with more force than the other side. This will cause a lead or pull to the side with least amount of positive caster.
effects of negative caster : a vehicle with negative caster will have a tendency to be easier to steer but will lack directional stability. It is also affected by any road surface variation such as small road irregularities or bumps. With the point of load pushing the tire along (negative caster), any bumps or road irregularities which are encountered have a tendency to immediately affect directional stability and vehicle handling.
cast steel : Steel that has been produced by the pouring of molten iron into a mold. Cast steel components are common due to their relatively inexpensive production process. It is not recommended to weld on cast steel by a hobbyist. This is why forged steel Ranger beams from earlier models are sought after to be extended/plated.
center of gravity (mass center) : The point at which the earth's gravitational force can be assumed to act on an object, for any calculations where the mass distribution is not important.
center mounted a-arms : a-arm suspension which has its inner pivots further inboard near the centerline of the chassis. This allows more wheel travel, with less angle on the balljoints/uniballs on the outer pivots.This suspension is used by most trophy trucks. Here is a picture of center mounted a-arms.
Checkpoint Carlos : n. roadside stop run by mexican military or law enforcement officials.
chromoly : a high strength, high stress steel commonly used in professional race car fabrication. Also known as 4130, this steel is often called "chromoly" because of the Chromium and Molybdenum concentration, which is around .80-1.10 for Chromium and .15-.25 for Molybdenum. The usual tensile strength for 4130 is around 95000-110000 PSI, however it can range as high as 225000 by proper heat treatment (also known as annealing).
cold rolling : a forming process in which metal is rolled or drawn through dies, usually at room temperature. This produces a product with certain advantages over hot rolled steel, such as tighter tolerances, increased properties, improved finish and straightness.
collision light : amber tinted lights which are faced rearward on a race vehicle or prerunner. These help gaining vehicles see that you are in front of them through the dark and/or dust. These aid in the visibility of the vehicle and are required for racing and recommended for the safety of any vehicle that goes to the desert. Also see dust lights.
compton : n. a stretch of off-road trail covered with half buried rocks.
CNC : Computer Numerical Control. A machining process where the entire process; tool cutter path, feed of tool, rotational speed of tool, and the linear or circular movement of the toolpath are all controled by machine. Using either direct operator input data MDI for some operations and CAM (Computer Assisted Manufacturing) to generate the toolpaths that the machine will follow.
coil : A steel wire that is wound into a coil shape and tempered in order to provide resistance to compression forces and store energy for release to the extended position.
coilover : combination of a race shock and coil in one unit. Uses a standard racing spring mounted on a threaded spring seat for ride height adjustment, and the shock resides inside the spring. Springs are available in any rate and any length thus allowing a complete customization of the suspension. Dual rate spring configurations also allow further tuning. Here is a picture of a coilover shock.
coil carrier : A coilover shock without valving. Usually used next to a bypass shock.
crossover steering : steering design for beam trucks made to move independently with the suspension and minimize or eliminate bumpsteer. Here is a picture illustrating the difference between stock and crossover steering.
cut and turn :modification applied to TTB suspension. This involves cutting the beam and re-welding it so as to maintain alignment after installing taller coils or raising the ride height.
CV joint : Constant Velocity joint, one that can transmit torque at an angle from one shaft to another without any speed variation. Commonly used in independent front or rear wheel drive suspensions.
deburr : to remove sharp edges.
delrin bushing : a self-lubricating polymer (plastic) used as an alternative to urethane bushings.
differential : the device inside the axle casing that allows each driven wheel to rotate at its own speed through a corner, while still getting one-half of all the available torque. Locked differentials distribute even torque to each side, rather than slipping, or being "open". Locked or limited slip differentials are quite helpful in situations where traction is needed.
dog launcher : n. an abrupt change in terrain sufficient to cause a dog to lose contact with front seat to truck bed. Dependant on how spoiled the dog is.
DOM tubing : Drawn Over Mandrel. Formed from strips and electric-resistance welded, then cold drawn to size. The cold drawing process causes the weld line to virtually disappear and gives the tubing it strength by cold working and allows consistent dimensions and tolerance. The carbon content also gives DOM (1020 or 1026) better mechanical properties than regular ERW tubing.
double click : n. two clicks of the microphone button. Signifies affirmative.
dual rate coilover : a coilover that features two different springs, each with different spring rates. This allows the compression and rebound of the shock to be postion sensitive.
ductility : the property that permits permanent deformation before fracture by stress tension.
dust lights : amber tinted lights which are faced rearward on a race vehicle or prerunner. These help gaining vehicles see that you are in front of them through the dark and/or dust. These aid in the visibility of the vehicle and are required for racing and recommended for the safety of any vehicle that goes to the desert.
duty cycle : the percentage of time during an arbitrary test period, usually 10 minutes, during which a power supply can be operated at its rated output without overloading.
elongation : the change in length of a tensile specimen expressed as a percent of the varying loads.
equal length beams : in stock form, the more recent line of beam suspension equipped trucks (Rangers, F-150s, etc) come with unequal length beams. This design changed a beam pivot, and was introduced to allow clearance for the driveshaft and third member on 4wd models. Equal length beams have near identical pivots and geometry from side to side, wheel travel is increased, and due to the lengthening and moving the pivots outward, the camber curve is better. When changing over an unequal length setup to equal length, crossover steering is highly recommended, as your bumpsteer will be greatly increased by keeping stock steering.
fatigue : the effect on certain materials, especially metals, undergoing repeated stresses.
federale : n. Meky officer of the law.
fiberglass : a laminate of glass fibers and resin, coated in a gel coat of some type, commonly used for body components. Fiberglass fenders and bedsides are flared out more than the stock sheet metal, allowing for greater tire clearance. Fiberglass is also up to 75% lighter than the steel body components.
flared bedsides : term used for stock sheet metal bedsides that have been extended outward allowing for greater tire clearance.
flatbiller : one who wears a flat-billed hat; without curvature. These creatures are often associated with irresponsible behavior and jumping on the bandwagon popularity of "prerunners". Note that one does not necessarily have to be wearing a hat to be classified as a "flatbiller". This is only the origin of the word, the attitude defines the term.
ford 7.5" : a cast steel rear end with a ring gear diameter of 7.5", produced by ford. This rear end is common on the smaller engine rangers. It is known to be a weak rear end, especially on desert trucks.
ford 8.8" : a cast steel rear end with a ring gear diameter of 8.8", produced by Ford. This rear end is commonly found on explorers, 4.0 liter equipped rangers, and later model F-150s . The explorer 8.8" is especially sought after by Ranger owners due to the much stronger 31 spline axles and being slightly wider (1.5").
ford 9" : rear end with ring gear diameter of 9". The housing is stamped and tubular steel, not cast, making it possible to truss the entire rear-end. The 9" is also among the strongest gear assemblies available, and lightest. The removable third member makes it possible to change gear ratios quickly. This is why the Ford 9" rear-end is the base for nearly all off-road race trucks.
forged steel : to form or shape heated metal by hammering. Also. the name of the unit used for heating metal, as the blacksmith's forge.
four link : suspension set up with four links to the axle for location. Usually, there are two lower trailing arms that are fixed to the rearend, with their opposite ends attached to the frame of the vehicle in a way which allows movement (usually heim joints); and two upper links which are attached to the top of the rearend and to the frame, attached at both ends allowing for movement. A coilover is commonly used for load bearing, and mounted upon the trailing arms.
four-oh-five : n. too much traffic.
fuel cell : fuel container constructed of metal, in which the fuel resides within a rubber bladder filled with foam. There is also a safety check valve which prevents fuel spillage in the event of a roll-over. A fuel tank designed for all around safety, and required by all racing sanctioning bodies.
full floating rear : axle construction which relieves the wheel shafts of cornering forces as well as the weight of the vehicle, so that it only has to cope with the torque from the rear differential. It also means the wheel shafts can be removed without removing the wheels.
gear ratio : the mathematical relationship between the number of teeth on the pinion gear and the number of teeth on the ring gear (or any two types of gears).
glass : slang term for fiberglass parts.
got-a-copy? : phrase. Do you hear me?
gotcha : n. a hazard that warrants a reduction in speed, usually hidden.
gusset : peice of metal welded between two other peices of metal, intended to inrease the strength of the bond by increasing the surface area of the weld.
harness : body restraint system (seatbelt) with 5 straps that converge to one spot. This type of restraint system is required by all racing sanctioning bodies, and is much safer than a standard seatbelt.
heim : spherical rod end used on many applications, from a-arm and link pivots, to steering. Here is a picture of a heim joint.
HID : acronym for High Intensity Discharge, a type of light that uses much less electrical energy while outputting much higher luminous energy (really bright lights that consume little power).
hot rolling : products that are rolled to finish at temperatures above the recrystallation temperature.
i-beam : a suspension design exclusive to Ford vehicles. This type of suspension includes beams and radius arms, with the beam connected to a spindle with balljoints or kingpin. A coil spring is used for load bearing. The pros of this design are strength, availability of parts, ease of travel gain, and race proven design. The cons are excessive camber change, a.k.a. sloppy travel. Although the geometry is not as desirable or controllable as an a-arm suspension, it has been proven in the desert.
IFS : Independent Front Suspension. This refers to suspension where the driver and passenger side move independently, and are not hindered by the opposite side like a straight axle would be. Both a-arms and beam suspension can be classified as IFS.
included angle (IA) : Included Angle is the combination of SAI and camber. Viewed from the front, the included angle is SAI plus camber if the camber is positive. If the camber is negative the included angle is SAI minus camber. If a side to side variation greater than ± 1.5° exists, check for vehicle damage. Angle + Camber = Included Angle (IA)
j-arm : two types of suspension components are referred to as "j-arms". If used in an i-beam context, this refers to the radius arm and i-beam being welded together, instead of traditionally bolted together. This creates a single unit of the beam and arm, known as a j-arm. This is done for strength purposes, although you should be reminded that if you bend a radius arm, you will need an entire unit to replace it. If these were bolted together, you would simply just replace the radius arm. The second part of this definition refers to the a-arm context. If someone refers to a j-arm on an arm suspension, this refers to a j-shaped upper control arm used to gain clearance for a coilover/bypass shock setup. Here is a picture of a billet upper j-arm from the Herbst truggy.
k-marker : n. kilometer markers for distances on Baja roads. Used for navigation purposes.
kingpin : the front wheels of most modern vehicles swivel around two ball joints, but on older vehicles, such as those equipped with older beam suspensions, they swivelled around bushes mounted on a shaft. The shaft is called a kingpin.
leaf spring : springs built-up from a number of flat plates clamped together. Commonly used on the rear of most production pickup trucks. Popular replacements for the harsh stock leaf springs are Deaver or National springs, which not only improve ride quality, but increase wheel travel amongst other things.
limit strap : a strap used to limit the droop of your suspension. This stops your suspension from drooping further, and prevents the shock from topping out or balljoints/uniballs from binding. Here is a picture of a limit strap installed on an a-arm Ranger.
limited slip (posi) : a differential unit that uses some form of friction to limit wheelspin by sending more torque to the wheel with the most traction.
load : overall force to which a material is submitted in supporting the weight of a mass, or in resisting an externally
locker : a differential unit that achieves maximum wheel traction by delivering 100% of the torque and power to both wheels.
long travel : general term referring to a new suspension replacement that increases wheel travel over stock. This type of suspension is available in kit form for many trucks or custom fab for all others.
manana syndrome : n. reason for any delay south of the border.
maytag : n. a large rock roughly the size of a home appliance that is at least partially on the course. The rock is positioned so that you may tag it or you may not.
MDR : Mojave Desert Racing sanctioning body. Visit the official MDR site here.
Meky : n. A Mexican National. Can be used as noun or adjective. i.e. Meky truck, Meky roads or just plain Meky. Not a derogatory term. Used to simplify radio communication.
MIG welding : Gas Metal-Arc Welding (GMAW). A welding process in which fusion is produced by heating with an electric arc between a metal electrode and the work. Shielding is obtained from an inert gas such as helium or argon. Pressure and/or filler metal may or may not be used.
mild steel : low-carbon machine steel.
misalignment : degree of movement achieved by a pivot. Here is a diagram showing the available misalignment of a uniball.
misalignment spacers : a machined spacer used with a spherical bearing to allow misalignment. High misalignment spacers are available to achieve maximum misalignment.
MORE : Mojave Offroad Racing Enthusiasts organization. For more information on races and rules, visit the official MORE site.
nerf : a freindly tap from bumper to bumper, making a vehicle aware of your presence. Commonly used in desert racing when a faster vehicle is approaching a slower one on a narrow stretch.
nitrogen : an inert gas used to pressurize a shock. This keeps pressure on the shock oil to prevent cavitation, or foaming, which will thin the oil ruin the shock's performance.
normalizing : heating steels to approximately 100 F above the critical temperature range followed by cooling to below that range in still air at ordinary temperatures. This heat treat operation is used to erase previous heat treating results in carbon steels to .40% carbon, low alloy steels, and to produce a uniform grain structure in forged and cold worked steel parts.
oversteer : the slip angle of the rear tires is greater than the front. Consequently, the turn-rate increases on its own and the driver therefore reduces the steering angle to compensate. During severe oversteer, the steering angle may reach full lock in the opposite direction while the vehicle continues on into the turn. The vehicle then "spins out."
parker pumper : air filtration system that blows filtered air to a special helmet, letting the racer breathe clean air.
photo-op : n. good spot for a picture.
pitch : rotation which occurs around a horizontal transverse axis through the center mass.
plasma cutter : a tool used to cut steel and other materials. Plasma cutters work by sending an electric arc through a gas that is passing through a constricted opening. The gas can be shop air, nitrogen, argon, oxygen. etc. This elevates the temperature of the gas to the point that it enters a 4th state of matter. We all are familiar with the first three: i.e., solid, liquid, and gas. Scientists call this additional state plasma. As the metal being cut is part of the circuit, the electrical conductivity of the plasma causes the arc to transfer to the work. The restricted opening (nozzle) the gas passes through causes it to sqeeze by at a high speed, like air passing through a venturi in a carburetor. This high speed gas cuts through the molten metal. The gas is also directed around the perimeter of the cutting area to shield the cut.
powder coating : uses very fine dry particles of resin with the pigment color of your choice. The resin powder is applied with a spray gun similar in concept to applying solvent based paint. The difference is this spray gun and it's resin contents are electrostatically charged. When the resin powder is sprayed onto a part it sticks to the metal because it's grounded, attracting charged resin powder like a magnet. The charged powder adheres to the metal then melted by baking at 400F degrees in special industrial sized ovens. The melted resin fuses to the metal, providing a uniform, thick and durable finish. The result is a beautiful glossy finish that is very resistant to chemicals, wear and chipping, 3 times stronger than solvent based paints. Powder coating simply provides a quality finish that can be seen and felt for years.
preload : used to set the suspension ride height. Not enough droop (too much preload) and the suspension will tend not to want to move initially, causing a rough ride over small obstacles such as stutter bumps. Too much droop (not enough preload) and the vehicle loses valuable travel, bottoming out easier and can cause stability problems. Any suspension (stock or aftermarket) can benefit from proper ride height adjustment.
prerunner : a vehicle used to pre-run courses for race trucks. A common misconception is that a prerunner is simply a lifted 2wd truck, but this is not the case at all. Prerunners come in all shapes and sizes, 2wd, 4wd, truck, buggy, etc. Many race teams build prerunners that have interchangeable parts with the race vehicle, and the prerunner can sometimes run a race in place of the race vehicle in severe cases.
protruck : a cost efficient, durable "spec truck" with its own racing organization. These trucks are designed as a dual purpose, low cost racing vehicle. They can be used as a short course and a long course high speed racer. The trucks race in a limited class, meaning that all of the trucks are built the same, using all of the same components with the exception of the body style and engine. For more information, visit the official Protruck website.
pucky : n. mixture of water from melted ice and any other combination of compounds, liquid or suspended solids, found in an ice chest.
quarter eliptic : link style suspension, but with leaf springs instead of coilovers.
rack and pinion : a type of steering setup. As the name implies, rack and pinion steering consists of two major components, a rack and a pinion. The rack, also known as a steering rack, is a long piece of metal that is flat on at least one side. The flat side contains teeth running the length of the rack. The teeth are cut perpendicular to the edges of the rack, meaning they run side by side from one end of the rack to the other, like teeth in a smile. The pinion, or more correctly, the pinion shaft, is a round rod that also has teeth on it, although these teeth run parallel to the length of the shaft, not lengthwise as on the rack. The pinion shaft comes into the rack at a ninety-degree angle, held in place by a collar, and the teeth on the pinion mesh with the teeth on the rack. The pinion is connected directly to the steering column, so when the steering wheel is turned to the left, for instance, the pinion rotates counter-clockwise (from the driver's perspective). The rotary motion of the pinion is changed to transverse motion by the rack. The rack moves to the right, making the wheels go left.
radius arm : a component of beam suspension. Wheel travel is hindered by the length and pivot of the arm, both of which are commonly modified. It is common practice to replace the stock radius arm with an extended one, preferably heim jointed instead of bushing to allow bind-free travel.
reach-a-round : n. act performed by a co-driver while extracting beverage from cooler in bed of pre-runner.
reservoir : a cylinder attached to a shock either by hose or tube, which flows the same rate of oil the shock displaces. The reservoir body has an internal floating piston which divides the oil and nitrogen it holds inside. The additional oil allows the shock to maintain cooler temperatures due to the extra volume, and the additional nitrogen helps keep pressure on the oil to prevent cavitation, or foaming/thinning of the oil, which will ruin the shock's performance. Here is a picture of the shock components.
roll : rotation that occurs around a horizontal longitudinal axis through the center mass.
roll cage : a tubular cage inside a vehicle's interior, used to protect the passengers in the case of a roll or accident. A properly designed cage can easily save the life of its passengers. It is stronly recommended to install a cage in any serious or recreational desert vehicle.
roll center : the center about which body roll takes place during cornering. The position of this center is determined by the suspension geometry.
SCORE : SCORE international off-road racing sanctioning body. Race information and schedules are available on the official SCORE website.
scrub radius : The distance at the road surface between the tire line and the SAI line extended downward through the steering axis. The line through the steering axis creates a pivot point around which the tire turns. If these lines intersect at the road surface, a zero scrub radius would be present. When the intersection is below the surface of the road, this is positive scrub radius. Conversely, when the lines intersect above the road, negative scrub radius is present. The point where the steering axis (sai) line contacts the road is the fulcrum pivot point on which the tire is turned. Here is a diagram explaining scrub radius.
shackle : the rearmost mount of a leaf spring. A shackle pivots to allow a greater growing rate of the spring. The stock shackle is commonly replaced with a longer aftermarket shackle for better performance. Here is a picture of a stock shackle, and here is a picture of a flipped hanger with Camburg shackle.
shackle flip : on Ford Rangers, this process refers to removing the rivets on the stock hanger/shackle assembly of the rear leaf springs, and re-installing it upside-down. This allows a better spring progression, and lowers the center of gravity. Replacement springs such as Deaver, are designed to work with a flipped shackle. Here is a picture of a stock shackle, and here is a picture of a flipped hanger with Camburg shackle.
shiny cactus : n. race course markers other than arrows used to indicate a hazard (see gotcha). Orig. Orange reflective tape seen usually at night affixed to trees, bushes and cactus to indicate impending hazard.
shock : dampens (smooths out) a movement or a vibration. The spring, not the shock absorber, absorbs road shocks. How it works: the shock body is filled with oil. The shaft has a piston attached to the end inside the shock body that controls how fast or slow it moves through the oil. By altering the internal valving, you can achieve the optimum performance of your shock for its application. As the piston moves up and down in the shock body, this creates heat. By pressurizing the shock with nitrogen, this suppresses the tendency of oil to cavitate, or foam, which will hinder shock performance. Here is a diagram of the shock components, and below is a list of what some of these parts do.
seal: a rubber or plastic cylindrical shaped piece that prevents oil from being lost from the damper.
shaft: the chrome rod on the shock that has a heim on one end and the piston and shims fastened to the other end.
shims: thin, steel, round, flat washers used to exert resistance on the oil flow through a piston. A series of shims (valve stack or valving) with varying outer diameters and thicknesses are arranged in sequence to provide a damping affect.
shock body: aluminum cylinder which contains the damper assembly.
transition shims: These are shims with very small outer diameters that are used to separate the normal shims of the low and high speed valve stacks.
shock revalving : fine-tuning service for altering the compression and rebound shims in order to affect a certain damping characteristic that keeps the vehicle's wheels following the terrain in many situations.
skid plate : plate, usually aluminum, used to protect areas prone to contact with the elements. Commonly used on front bumpers to protect the radiator and steering, and also under the chassis on extreme duty race vehicles.
SLA : Short-Long Arm suspension. This is the common type of a-arm where the upper arm is shorter than the lower arm, rather than being the same length. This provides negative camber gain on compression.
slip angle : the flexibility of a tire causes the longitudinal centreline of any wheel to deviate from the path followed by the contact patch centerline, as soon as the steering wheel is turned from the straight-ahead position. The angle between the wheel centerline and the contact patch centerline is called the slip angle, and each wheel will normally run at a different angle, because its value depends on a number of factors. These include suspension geometry, tire construction, tire pressure and cornering speed. The difference between the average front and rear slip angles will determine whether a car oversteers or understeers.
SNORE : Southern Nevada Off Road Entusiasts sanctioning body. More information can be found on their official website here.
solid body mounts : solid machined blocks used to replace the stock body mounts when building a roll cage. When a vehicle is caged by welding points to the frame, the body will flex on the stock mounts and can cause cracks since the frame is stationary. Solid body mounts keep the body in relation to the frame without flexing, and prevent cracking.
spindle : the upright/knuckle combination which moves about 2 pivots and steers a vehicle. Here is a picture explaining the basic components of a-arm suspension, the spindle concept remains the same for other suspension types..
spring plate : plate which clamps the leaf springs to the axle, fastened with u-bolts.
spring rate : the amount of force necessary to compress the spring, usually measured in one inch increments. A straight rate spring will take the same amount of force for the entire travel of the spring. A 500 lb rated spring will take 500 lbs of force to compress it one inch, another 500 lbs (total 1000) to compress it the second inch, and so on until the end of the spring travel. Now a progressive rate spring changes the force requirement as the spring is compressed. A 500-600 lb rated spring will require 500 lbs of force to compress the spring the first inch, another 520 lbs (varies depending on spring length) to compress it the next inch all the way to the last inch where an additional 600 lbs of additional force is required to compress.
sprung weight: weight of the vehicle that loads the suspension. Equal to the overall weight minus the unsprung weight.
steering axis inclination (SAI) : The angle between the centerline of the steering axis and vertical line from center contact area of the tire (as viewed from the front). SAI is typically not adjustable, but deviations from specification can indicate vehicle damage. A maximum variation side to side of ± 1.0° may also indicate vehicle damage. SAI urges the wheels to a straight ahead position after a turn. By inclining the steering axis inward, it causes the spindle to rise and fall as the wheels are turned in one direction or the other. Because the tire cannot be forced into the ground as the spindle travels in an arc, the tire/wheel assembly raises the suspension and thus causes the tire/wheel assembly to seek the low (center) return point when it is allowed to return. Thus, since it has a tendency to maintain or seek a straight ahead position, less positive caster is needed to maintain directional stability. A vehicle provides stable handling without any of the drawbacks of high positive caster because of SAI. Here is a diagram explaining SAI.
stress : internal force or resistance developed in steel which was hardened, extensively machined, or cold worked.
stress relieving : a process of reducing residual stresses in material by heating to a suitable temperature and holding for a suffient time. this treatment may be applied to relieve stresses inducted by casting, quenching, normalizing, machining, cold working or welding.
sway bar : properly called an anti-sway bar, these steady the chassis against front end roll and sway on turns. Stabilizers are designed to control this centrifugal tendency that forces a rising action on the side toward the inside of the turn. When the car turns and begins to lean over, the sway bar uses the upward force on the outer wheel to lift on the inner wheel, thus keeping the car more level.
swifties : n. large rolling hills situated so that high speed travel causes vehicle to launch off crests, land in valleys and launch again off next crests with enough force to cause next landing to be crossed up and out of control.
tapping : process of cutting screw threads in a round hole with a tap (an internal thread cutting tool).
tensile strength : the property of a metal which resists force applied to pull it apart.
three link : rear suspension set up with three links to the rearend. There are two lower trailing arms that are fixed to the rearend, with their opposite ends attached to the frame of the vehicle in a way which allows movement (usually heim joints); and one upper trailing arm which is attached to the top of the rearend and to the frame, attached at both ends allowing for movement.
tie rod : rod connecting to the spindle that controls steering.
TIG welding : Gas Tungsten-Arc Welding (GTAW). A welding process in which fusion is produced by heating with an electric arc between a tungsten electrode and the work while an inert gas forms around the weld area to prevent oxidation. No flux is used.
toe : The difference in the distance between the front of the tires and the rear of the tires on the same axle, or to the vehicle centerline. Toe-in, or positive toe, is defined as the front of the tires being closer together than the rear of the tires. Toe-out, or negative toe, is when the rear of the tires are closer together than the front of the tires. Zero toe is when the tires are parallel to each other. Excessive toe increases tire scuffing and results in tire wear and drag on the vehicle. Excessive toe-in, or positive toe, increases scuffing on the outside of the tire. Excessive toe-out, or negative toe, increases scuffing on the inside of the tire, and in some cases can cause a darting or wandering problem. Bias or bias-belted tires will commonly show a featheredge or saw-tooth toe wear pattern across the entire tire tread area. Any tire wear pattern caused by a toe condition can be further affected by an excess camber condition and may result in irregular wear patterns. Here is a diagram explaining toe settings.
tolerance : the allowable deviation from a standard size; the total amount by which a specific dimension may vary; thus, the tolerance is the difference between the maximum and minimum limits.
torsion bar : uses the flexibility of a steel bar or tube, twisting lengthwise to provide spring action. Instead of the flexing action of a leaf spring, or the compressing-and-extending action of a coil spring, the torsion bar twists to exert resistance against up-and-down movement. Two rods of spring steel are used in this type of suspension. One end of the bar is fixed solidly to a part of the frame behind the wheel; the other is attached to the lower control arm. As the arm rises and falls with wheel movement, the bar twists and absorbs more of the road shocks before they can reach the body of the car. The bar untwists when the pressure is released, just like a spring rebounding after being compressed. Adjusting the torsion bars controls the height of the front end of the vehicle. The adjusting bolts are located at the torsion bar anchors in the front crossmember. The inner ends of the lower control arms are bolted to the crossmember and pivot through a bushing.
torque : the rotational equivalent of a force, and is calculated by multiplying the force causing rotation by the perpendicular distance from the line of action of the force to the centre of rotation. The unit is the newton metre.
trackwidth : measurement taken from the outside of the passenger side tire to the outside of the driver's side tire. This measures how wide your front or rear is. Some racing classes have strict rules for trackwidths, and must be kept within a certain range.
trailing arm : a suspension arm that is mounted so that it points to the rear of the vehicle, used to locate the rear axle. Usually used on link suspension, where the coilover mounts.
triangulation : diagonal bracing that effectively adds strength to a structure.
truggy : a sort of combination truck and buggy, similar to an open wheeled trophy truck.
TTB : Twin Traction Beam, the 4wd version of i-beams.
tube bender : a tool used to bend tubing. Uses die sets to bend different diameter tube to a desired angle. Some die sets allow up to 90º bends, while others allow up to 180º. These are available in either manual or hydraulic models. The manual style uses a rachet handle to slowly bend the tubing, while the hydraulic model uses a hydaulic ram to aid in the bending, which of course is much pricier. Some popular benders are JD Squared and Pro Tool. Here is a picture of a tube bender.
u-bolt : u-shaped bolt connecting the axle to the leaf spring pack.
understeer : results when the slip angle of the front tires is greater than the slip angle of the rear tires. A greater steering angle is then required in order to maintain the turn. When the steering angle reaches full lock and the turn cannot be maintained, the vehicle drifts to the outside. In an understeer condition, the driver is attempting to negotiate a turn, but the vehicle mushes ahead refusing to cooperate.
uniball : spherical bearing often used to replace factory balljoints. These allow high misalignment and greater strength.
unsprung weight : measurement of the weight of everything outboard of the wishbones or suspension links, plus 1/2 of the weight of the wishbones or links and spring/shock. It has a great effect on handling. Here is a diagram below showing why unsprung weight is so important.
vado : n. dip or depression in road usually caused by perpendicular drainage. Often a danger area.
viscosity - a rating system for oils that measures the oil's flow rate through a fixed orifice at a certain temperature. Also known as the oil's weight. Example: SAE 30 Wt.
the “w” : n. the shape of the trail caused by 4 wheeled vehicles digging away at the topsoil. A deep “W” is caused by heavy use by high horsepower vehicles. A constant source of joy for members of DIRT FIRST! A reason to whine for the Sierra Club.
washboard : 1) n. rippling effect on graded, hardpack roads caused by slow moving, poorly suspended vehicles disrupting the road surface with wheel hop. 2) v. To create a washboard surface on a road by driving slower than conditions allow.
wheelbase : distance from the centerline of the front hub to the centerline of the rear hub on the same side, parallel to the vehicle centerline. Here is a diagram explaining wheelbase.
wheel backspacing : measurement from the mounting pad to the inner edge of the wheel.
wheel offset : the distance from the mounting pad to the centerline of the wheel.
wheel rate: spring rate times the square of the spring mechanical advantage
wheel travel :distance of vertical suspension movement measured at the hub centerline. Here is a diagram explaining wheel travel.
Whiplash : racing sanctioning body. More information can be found on the official Whiplash website.
work hardening : increase in resistance to deformation (hardness) produced by cold working.
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yard sale : n. the results of an off-road crash. Contents and parts of the vehicle are spread over the desert. Aftermath of a bad trip through the swifties.
yaw : rotation about the vertical (also called polar) axis through the center of mass of a vehicle