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Front suspension terms explained

Discussion in 'The Hokey Ass Message Board' started by 50dodge4x4, Mar 5, 2008.

  1. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,535


    It has occured to me that there may be many folks here that are just begining their hot rod additions, and may not know what the terms we throw around mean. So, with this in mind I will try to explain in simple words what some of these terms mean.

    Tires = These are the rubber componets of a car that contact the road. There are two bassic types of tire construction, Bias Ply and Radial.
    Tires are built from a foundation of cords chemecally bound together to form layers of material called plies. The plies in the tires run from one side to the other across the tire and attach to a wire bead the forms the edge of the tire. All tires have at least 2 layers of plies and many have several more plies. The more plies, the stiffer the tire and the more weight it can carry. Truck tires often have 8 layers of plies.

    In a Bias Ply tire, the cords in the plies run at an angle from one bead to the other. The second ply would run at the same angle in the oppisite angle forming a X pattern between the two plies. Nearly all of the tires built before the 60s were bias ply tires.

    In a Radial tire the plies run across the tire in a straight line from bead to bead.

    Both bias ply and radial tires have what they call tire belts. The "belts" are additional plies that run around the tire under the tread only. The cords in the belts usually run in a direction around the tire. The belts give extra strength and stiffness to the tread surface and may be made of many different materials.

    Wheels = These are the things the tires mount to that connect the tires to the car. They may be made from steel, aluminum, magnisuem or even plastic or other material.

    Hub= These are the things the wheels bolt to. They may be part of brake drums, or part of rotors or free standing by them selves. The hubs are attached to the vehical by the wheel bearings and are what allows the wheel to rotate.

    Spindles= Spindles are the part the hubs and wheel bearings ride on. They are the part that allows the hubs to turn right and left. The spindles are formed so a pair of vertical machined holes (one at the top and one at the bottom with about 2"-3" spacing between the holes) at the axle end of the spindle.

    Axle= This one is a bit tricky. Sometimes the word axle refers to everything between the wheels, side to side, as in the front axle or the rear axle.
    The traditional meaning is the actual componet itself. It is a formed beam or tube that connects the right side spindle to the left side spindle and passes across the car from side to side. Axles gennerally have a lower center then outside ends to clear engines, springs and such. A "dropped axle" mearly means the axle has been reworked so that the center is lower then normal. The point on the axle ends where the spindles are attached are originally formed and machined to accept a vertical hole in the axle about 2"-3" high. The machined holes on the spindle match up with the machined hole in the axle and a "king pin" , a machined pin, passes through the machined holes. Gennerally, there are machined bronze bushings pressed into the axle holes that fit between the axle and the king pin to allow movement and wear. The spindles are held in a vertical position on the axle by the bronze bushings and do not move vertically on the axle. The king pin is what allows the spindle to turn right and left on the axle.

    Independent Suspension= an axle split to allow movement independent of each other side to side. Generally a pair of arms replace the axle on the right and left side of the car. These arms are called "control arms". Many vehicals have two arms per side, these would be called "upper control arms" and "lower control arms". The control arms have brackets to hold bushings (normally hard rubber). The bushings are attached the the vehicals frame by brackets welded to the frame and are bolted on. The spindles are attached to the control arms by "ball joints". The ball joints allow up and down movement as well as turning movement of the spindles from the control arms. Through out history car companies have tried several versions of both the beam axle and independent suspension and have on occasion mixed both componets.

    Tie rods= reguardless of which suspension system used, if it turns, you want both wheels turning the same direction. This is accomplished by tie rods. Tie rods connect to both spindles at either the front on both sides of the car or at the rear of both sides of the car. A car having the tie rods at the front of the spindle, or ahead of the axle are called "front steer cars" and cars having the tie rods at the rear, or behind the axle are called "rear steer cars". Since adjustments have to be made, the tie rods have to be adjustable. On a beam axle car, the tie rod is broken into 3 sections. A right "tie rod end" the "adjusting sleeve" and the left tie rod end. To make adjusting easier, one tie rod end is threaded with left hand threads and the other tie rod end is threaded with right hand threads. The adjusting sleeve has left hand threads cut into one end and right hand threads cut into the other end. Then one mearly needs to turn the adjusting sleeve clock wise or counter clock wise to move the tie rod ends closer together or farther apart. There are either lock nuts or clamps that crimp the adjusting sleeve to prevent movement once the desired adjustment is set. Most tie rod ends are designed similarly to a ball joint to allow turning and up and down movement. Many times the tie rod assemble is split into 3 major componets, a right hand side, a left hand side, and a "center link" between the right hand and the left hand side. In this case, the right hand side would have a tie rod end on the outside edge (wheel side) called an "outside tie rod end", an adjusting sleeve, and another tie rod end on the inside edge (centerlink side) called the "inside tie rod end". The left hand side would be the same way, inside tie rod end, adjusting sleeve, and outer tie rod end. There would not be another adjusting sleeve on the tie rod assembly. This is often done with independent suspension. The tie rod adjustment is what maintains the relationship between both front tires pointing in the same direction. "toe out" is where the front of the tires are farther apart the the rear of the same tires. "Toe in" means the front of the tires are closer together then the back edge of the same tires.

    Springs are used to support the suspension and give confort to the cars riders. There are many forms a spring can take. A "coil spring" is a coil of spring steel designed to collasp and rebound in a confined area. A "leaf spring" is a flat long spring designed to attach flex between the ends and the center. Leaf spings have horizontal holes in the ends called "spring eyes" that are used to mount the ends of the springs and "center bolts" that are bolts through the leaf spring surface used to locate things bolted to the center of the spring. "U bolts" are used at the center of the leaf springs in conjunction with "spring perches" and "spring plates". U bolts are bolts bent into a U shape to go around either the spring or the mounting surface. Spring perches are the componet that holds an axle onto the center bolt. Spring plates are the plates the u bolts pass through.
    A leaf spring may be attached to the frame at both ends with the sprung weight in the center, or it may be mounted in the frame at the center with the sprung weight at one or both ends. Leaf springs may be used singly or in pairs. Because leaf springs are designed to flex, mounting brackest have to be designed to allow some movement. This is accomplished be use of "spring shackles" or bar stock on either side of the spring with bolts passing through rubber bushings in the spring eyes.
    "Torsion bars" are springs in the form of a round bar with hex shaped ends. Torsion bars are designed to twist and untwist. Torsion bars are mounted to the frame on one end with "anchor pins" or brackets designed to hold the hex head from turning. The other end of the torsion bar is attached to the axle with a leverage arm or to the control arm.
    No discussion of springs would be complete without discusing "shock absorbers". Because springs are designed to spring, they move in both directions until they finally stop moving. On a car this uncontroled movement is undesirable. Shock absorbers (also refered to simply as "shocks") are what controls the spring movement, or more accurately they absorb spring movement. Shocks were not ever intended to be used as a ride hight adjustment device.

    To complete this discusion we need to cover steering. Obously something has to happen between you turning the steering wheel and the movement of the tie rod ends. The steering wheel is attached to the "steering shaft" which is a shaft about 3/4" in diamiter that passes through the "steering column". The steering column is the outside housing that supports the shaft and is connected at the floor board and the dash board. A "tilt column" has the ability to move up and down beyond the dash board. The housing has a complex joint and the steering shaft has a joint it it. A "collaspable column" is designed to crush in an accident. A section of expanded metal replaces the hard column, generally between the floor and the dash and the steering shaft is split with a hollow section that has a series of hard plastic pins holding it together. Upon an accident, the plastic pins shear and the shaft moves through the hollow tube, at the same time the expanded metal crushes. Beyond the firewall, the steering shaft mechanically connects to the steering system. Once again, there are two primary steering systems.

    A "rack and pinoin" steering consists of a pinoin shaft that connects to the steering shaft. The pinoin is geared and permently positioned in a housing with a movable toothed rack. As the pinoin turns, it moves the rack left or right. The inner tie rod ends would be attached to the corosponding ends of the rack and the rack replaces the centerlink.

    The second choice is with a steering box. The "imput shaft" attaches mechanically to the steering column steering shaft. The imput shaft is mounted by bearings or bushings to the "steering box" and is a "worm shaft" The "out put shaft" is a "recirculating ball nut" also mounted to the steering box with bearings or bushings. The process changes a rotating movement to a swing movement. One end of the "pitman shaft" attaches to the out put shaft and the other end attaches to the centerlink or to the tie rod assembly if a beam axle is present. If a centerlink exists, at least one end of the center link needs to be supported. The support part is called an "ideler arm" and there may be one or two idler arms to support the center link, depending on the system design. Power steering is mearly a hydralic assist by an engine driven pump forcing fluid through orfices to ease steering effort. Both rack & pinoin and steering box systems can be power assisted, though special componets will be required.

    Again, there have been several different versions of both steering systems.
    Hope this helps someone.
  2. fleetside66
    Joined: Nov 20, 2006
    Posts: 2,555


    Thanks Gene. You're right. I'm in the middle of my first build & I'm finding out exactly how much I don't know. Your tutorial helped.
  3. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,535


    Thanks man, its nice to know at least someone got something out of all that typing. :D Gene
  4. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008


    do yur fingers hurt?

    nice writeup gene, well worded even for retards like myself :p

  5. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,535


    Yep, both of em!

    You know I type with 2 fingers right? Typing class drop out here, if the letters wasn't on the keys I'd be screwed. :rolleyes: Gene
  6. keeper
    Joined: Jul 24, 2006
    Posts: 400

    from So Cal

    Awesome post...thanks
  7. Bluto
    Joined: Feb 15, 2005
    Posts: 5,113

    Member Emeritus

    People forget just how important suspension geography can be :)


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