Glossary Of Terms
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A-2
Term used for tire sizes 16.00 and larger in nominal cross section. Also referred to as earthmover or off-the-road tires (O.T.R.).
Aging
Deterioration of rubber properties by oxidation over a period of time.
Alignment
Wheel alignment is the mechanics of keeping all interrelated parts which affect steering in proper adjustment. There are five steering angles involved:
(a) Camber
The inward or outward tilt of the wheel at the top from the vertical. Positive tilts outward and negative tilts inward. It is measured in degrees. (b) Caster The forward (negative), or rearward (positive) tilt of the kingpin at the top from the vertical, when referring to trucks. In cars having independent front suspension, the upper ball joint is set forward or rearward in relation to the lower ball joint. Caster is measured in degrees. See 'trail distance'. (c) Toe-in/Toe-out The front tires of a vehicle are adjusted closer together in the front than at the back for toe-in. The opposite setting is toe-out. It is measured in fractions of an inch. (d) Kingpin inclination/steering axis inclination The inward tilt (side to side) of the kingpin or spindle support arm, at the top, from the vertical. Thus a line drawn down through the centre plane of the tire and a line through the kingpin, or ball joints, would come closer together at the ground than at the top. See 'centre distance'. (e) Turning radius (Toe-out on turns) The front tires assume a toe-out relationship to one another when making a turn. This makes allowance for the fact that they are forming different size circles around a common centre. (Sometimes called the Ackerman System). Ambient temperature
The surrounding air temperature.
Angular vibration
Side to side movement or shimmy of a tire. See 'BALANCE, DYNAMIC.'
Anti-skid system
Computer Brake Control. A system installed on many vehicles to prevent skids caused by wheel lock-up. It allows for automatic adjustments in braking pressure for maximum braking force without loss of steering control.
Aquaplaning
See 'hydroplaning'.
Aspect ration
The ratio of 'section height' to 'section width'. Section height divided by section width of a tire expressed as 78 series, 70 series, etc. The section height is 70% of the section width when referring to 70 series. These are low profile tires, and may be called ultra low profile.
Awl
A pointed or flat tool used to probe nail holes and injuries.
Axle live
Driven axle.
Axle, ratio
See 'GEAR RATIO'.
Balance patch
A factory installed patch used to bring a tire within quality control balance tolerances before distribution. It is placed inside the tire casing and looks much like a nail hole repair patch.
Tire balance
A tire properly weighted so that it rotates without causing bounce or vibration: Unbalance A tire that is not weighted properly can cause vibration. The condition is exaggerated by centrifugal force which increases as speed is increased and by the distance the heave spot is from the wheel axis. (See 'ounce inches'.) Static balance - (kinetic) A tire that has a heavy spot at any point around its circumference. The heaviest point will come to rest at the bottom when the tire is rotated on a free bearing. On a vehicle, the tire will tramp or bounce. Dynamic unbalance Exists only when the wheel is rotating and is caused when a heavy spot in the tire is not in the centre plane of the wheel, or when a heavy spot is not in the same plane as the static counter-balance weight. On a vehicle the tire would wobble from side to side. On-car-balancing Balancing of tire using a machine capable of balancing tire, wheel and brake assembly while the tire is properly mounted on the vehicle. Off-car-balancing The tire assembly is removed from the car and mounted on a balancing machine.
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Cab
Driver's compartment of a truck.
Calcium chloride
Chemical added to prevent freezing of water ballast in farm tires and EM tires.
Calendering
A thin layer of rubber inside the tire casing covering the carcass cords, protecting them from moisture and giving protection to the tube against chafing by the cord-body. In tubeless tires, calendering consists of a layer of air proof rubber (Butyl).
Camber
See 'alignment'.
Camber axle
An axle beam formed in a slight arc, curving upward at the
centre to allow the tires to tilt outward at the top. It compensates for normal axle sag under load.
Capping
See 'retreading'.
Carbon black
A by-product of the petroleum industry used as a pigment and to give body in the manufacture of rubber products, both natural and synthetic. Carbon is the black residue from burning petroleum.
Carcass
The cord body (ply/plies). The foundation structure of a tire that provides strength to hold air pressure within the casing.
Carrying capacity
The maximum load that should be permitted on a given tire, wheel, or rim, etc., as recommended by the manufacturer's data book.
Casing
The tire without tube, flap, or tim.
Casing factor
That portion of the load supported by casing stiffness instead of air pressure.
Caster
See 'alignment'.
Cement
An adhesive rubber compound dissolved in solvent used to provide building tack and cured adhesion. May be brushed or sprayed on the buffed surface.
C.G.
Centre of gravity. A point within the length, width, and height of a vehicle about which all the vehicle weight is balanced.
Chain drive
Rear axle driven by means of a chain belt.
Change-over
Removing new original equipment tires in trade for a different make, size or type.
Channel
See 'groove'.
Chassis
The basic truck frame, including suspension, steering, driving and power components, excluding cab or body.
Chassis, cab
Truck chassis including driver compartment.
Chassis, cowl
Truck chassis with front fenders and hood complete with instrument panel. For use with custom built body and cab.
Check valve
A one way valve used to prevent pressure loss.
Checking
Minute cracking in surface of rubber caused by aging and oxidation.
Chemical cure
Vulcanization at room temperature or above, activated by chemical agents without the application of heat from an outside source.
Chipping
Flaking or tearing away small bits of tread rubber.
Chunking
Tearing or breaking away pieces of tread rubber
Circumferential break
A tire injury running parallel to the bead.
Circumferential crack
A crack in a tire running parallel to the beads. Usually consists of cracks in the grooves of the tread
Clearance
Between dual - See 'dual spacing'.
Vehicle to tire: Minimum -
A. To a fixed part: 5/8' (15mm) B. To a moveable part: 1' (25mm) Vertical The distance between the top of the tread and some part of the vehicle closest above it, after subtracting the axle stop clearance and any increase in tread depth from the existing tire. Longitudinal The distance between the tread and the closest point forward or rearward, reduced by increase in tread depth and rearward movement of the axle under load (1/3 the distance between shackle pin centres). Lateral he distance between the tire sidewall and the nearest point on the vehicle, reduced by any increase in rim offset and 1/2 any increase in tire section from the existing tire. Front wheel clearance The distance between the tire and the closest point on the vehicle laterally, longitudinally and vertically, checked to lock and all intermediate points. Coefficient of friction
The horizontal force required to move a body (on a relatively smooth level surface) divided by the weight of the body. The coefficient of rolling friction is the maximum retarding force (that can be applied to a rolling body on a relatively smooth level surface without causing a cessation of rolling) divided by the weight at the contact surface.
Coil spring
Spring stock coiled in cylindrical form.
Commercial tires
Generally indicating truck and industrial tires.
Conventional tire
See 'bias-ply'.
Containerization
Shipping system based upon large cargo-carrying containers that can be easily interchanged between trucks, trains, and ships without rehandling of contents.
Contract carrier
An operation transporting under contract with an individual shipper.
A strand of fabric material or steel cable used in the ply of a tire.
Cost per mile
The actual cost of a tire after considering all costs (price of tire, price of retreads, repairs, services, etc.) less any credits (warranty, etc.), divided by the total number of miles it has run. True cost per mile can be figured only after the tire is no longer serviceable and should include costs to the user incurred as a result of downtime.
Cracking tread or groove
Splitting in grooves caused by excessive strain. Cross section
See 'section width'.
Cross member
Structural shape tying in side rails of frame.
Crown
The tread area of a tire.
Crown radius
The measurement of the curvature of a tire tread between the shoulders of the tire. Expressed as a percentage, it indicates the relative flatness of the tire tread area.
Crown width
The distance shoulder to shoulder measured along the buffed contour.
Cure time
The time required at a reference temperature for a compound to reach optimum physical properties.
Curing
Process of heating or otherwise treating a rubber or plastic compound to convert it from a thermoplastic or fluid material into the solid, relatively heat-sensitive state desired in the commercial product. When heating is employed, the process is called vulcanization.
Cushion gum
A soft, tack rubber compound used in retreading and repair to facilitate bonding between different rubber compounds and between plies, etc.
Dead axle
The non-powered axle of a tandem rear mounting in which the other axle is powered.
Deflection rate
Generally refers to rate of spring deflection to inches per 1000# load.
Demountable rim
See 'rim and wheel terms'.
Differential
An arrangement of gears at the
centre of a drive axle that allows the wheels on one side to go faster (or slower) than wheels on the other side, as in rounding curves.
Directional tread
An arrangement of bars, grooves and ribs in any manner that gives most effective traction when the tire revolves in only one direction.
Disc wheel
The combination of a rim and a metal disc riveted or welded together. The disc is usually offset from the
centreline of the rim to allow for dual tire mounting and to provide sufficient clearance between duals. Disc wheels are attached to the hub with either single nuts or double cap nuts.
Dish
Offset. See 'rim and wheel measurements'.
DOT.
Department of Transportation, a federal agency.
DOT number
The symbol DOT means the tire meets or exceeds Department of Transportation safety standards. Following DOT are a maximum of eleven numbers.
Example: DOT FT TW A2NX 092:
DOT-Meets or exceeds standards. FT-Identifies manufacturing plant TW-Code for tire size. A2N or A2NX-3 or 4 digits optional with manufacturer to identify characteristics of the tire. 092-Week of mfg., in this case, 9th week of 1972. Prior to May 22, 1971 only the manufacturer's plant was identified by three numbers -- (Example DOT 129). Retreaded tires must also have a new serial number and can be determined by the letter "R" following DOT letters.
Dowel pin
A pin aligning or securing two parts to prevent movement between them.
Downtime
The vehicle operating time lost due to maintenance difficulties, tire damages, etc.
Drag link
Connection between Pitman Arm and Steering Ball (Steering Arm) on front axle of a vehicle.
Drift
See 'tire deviation angle'.
Drive train
Components used to propel vehicle.
Drivers
Drive axle tires (slang usage).
Drivers, rim
Riveted or welded metal blocks or extrusions on both sides of the valve slot to prevent valve damage due to rim slippage on cast spokes.
Drop centre rims
See 'rim types'.
Dual axles
See 'tandem axles'.
Dual bead tires
Heavy service and large truck tires using two or more sets of bead wires in each bead rather than one.
Dual mountings
Tandem axles, both powered directly by the engine. (Slang term, twin screw.)
Dual spacing
A measurement in inches from the
centre of the tread of one tire, to the centre tread of the other tire in dual, which provides clearance between duals for air circulation.
Dump body
Metal body generally hinged at rear and dumped by hydraulic means. Size generally given in cubic yard water level capacity.
Durometer
A device to indicate the hardness of rubber.
Dust cover
A soft, flexible valve cap to protect valve assembly from dust while in shipment and storage. It is not capable of sealing the air pressure and should not be used in service.
Dust shield
Sheet metal disc or plate placed on brake assembly to keep debris from brake assembly.
Dynameter
Electric or hydraulic instrument used in determining power output of engine, or friction in chassis components.
Dynamic balance
See 'balance'.
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Gross combination weight (GCW)
The weight of a truck and trailer combination and its entire contents.
Gross train weight (GTW)
Gross train weight. Same as GCW.
Gross vehicle weight (GVW)
Total weight of fully equipped truck and payload.
Gear ratio
The number of revolutions of a driving gear required to turn a driven gear through one full revolution. For a pair of gears the ratio is found by dividing the number of teeth on the driven gear by the number of teeth on the driving gear. Changing tire size will change the effective gear ratio. An increase in loaded radius will increase ratio, increase speed and reduce power.
Glad hands
A separable mechanical connector used to join air line hoses when combination vehicles are coupled together.
Green tree
The complete rubber/fabric/steel just before being cured.
Groove
The channel between ribs in the tread of a tire.
Grooving
The cutting of a tread design into tread rubber where a design does not already exist. Also altering an original design, i.e. cross-grooving to increase traction.
Groove cracks
Splitting or cracking of the rubber (under
tread) at the base of the grooves, between tread ribs. Primarily caused by growth in textile casings.
Growth, tire
The stretching of textile tire cord materials due to heat and loss of strength, resulting in the casing increasing in size.
Gutter, bevel
See rim terms. |
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Heel & toe wear
Uneven wear of tread blocks on a tire. The trailing edge of the block often tends to wear at a faster rate that the leading edge.
Helper spring
Additional spring device permitting greater load on axle
Hub
The base having studs protruding from its face upon which the wheel is mounted to the vehicle.
Hub Odometer
A register showing miles travelled by vehicle mounted directly on the axle hub. It is popular to record mileage for leasing of vehicles or tires particularly on trailers, since there is no other odometer present.
Hydrostatically inflate
To inflate with water in place of air. (Also see liquid ballast).
Hydroplaning
Loss of road contact due to the
build-up of water between tire tread and road surface. It occurs when factors, including speed, water depth, tread depth and inflation pressure, so combine that lifting force is exerted under the tire.
Hysteresis
The energy lost and not returned, when tire materials are subjected to stress in any direction. Lost energy is converted to heat through molecular interaction, and since rubber has poor thermal conductivity, internal temperatures of a tire can build up rapidly under repeated flexing. |
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Impact break
Rupture to a tire resulting from shock of striking a chuck-hole, rock curb, etc. and not caused by cutting.
Included angle
The sum of the camber and kingpin inclination angles. This angle is designed into the steering knuckle and must remain constant
Independent suspension
One wheel position can move vertically without imposing any corresponding movement on the other wheel on an axle. The straight axle had been eliminated and replaced with upper and lower A-Frames (control arms) that pivot at the individual wheel position.
Industrial tires
Heavy duty tires, for use on forklifts, lowbed trailers, etc.
Industrial solid-A non-pneumatic tire, used most often on forklifts where flats are a constant problem. Inertia
The tendency of a body at rest to remain at rest and a body in motion to persist in motion.
Inner cap nut
See dual mountings.
Inner tube
A tire shaped air chamber, containing a valve and placed inside the tire casing. It seals in the air which supports the load, but is not capable of supporting the load without the strength of a tire and rim surrounding it.
Inter-axle differential
Gear device equally dividing power between axles and compensates for unequal tire diameters. |
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Jack
Mechanical, hydraulic, or pneumatic lifting device to raise chassis for repairs or tire changes.
Jack-knifing
The trailer over-turns the tractor, pushing the tractor drive wheels sideways, forcing the combination into a V-shaped attitude, resulting in a complete loss of control with no possibility of recovery. |
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Kinetic balance
See balance, static. |
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Kissing between duals
The intermittent contact of tires in
dual as they flex; caused by inadequate dual spacing or by overload. |
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Laden weight
See gross vehicle weight (GVW).
Lading
The load; the freight in a vehicle
Lateral clearance
Smallest distance laterally between the tire and the nearest fixed point of the vehicle.
Lateral run-out
A tire assembly that does not run true to its plane; i.e., a damaged wheel moving in a wobbling, side to side manner.
Lateral stability
Limiting side movement.
1. Tread grooves running circumferentially around the tire resist side forces for maximum traction on turns.
2. Stabilizing tread plies limit side to side movement of the tread ribs caused by the expansion and contraction of tread areas as sidewalls flex.
Load base
Used in calculating load distribution; it is the distance between the
centre of the rear axle (or centre between tandem axles) and the centre of payload.
Negative load base If centre of payload is behind the rear axle, it is negative and takes load off the front axle. Load distribution
(Distribution of load on truck or trailer chassis.) The relationship of the gross load on the front and rear axles to the total gross load.
Load distribution calculation
Payload on the front axle is equal to the total payload multiplied by the load base (in inches) and divided by the wheelbase (in inches).
To complete the calculation of load per axle, it is necessary to obtain the unladen weight of the vehicle and estimate its breakdown by axle. Load & inflation table
A chart in the tire manufacturer's data book listing the carrying capacity of a tire at each of several air pressure increments from the lowest range of practical usage to its maximum capacity.
Load range
An index of tire strength which replaces the ply rating system and its predecessor which listed the actual number of plies.
Load radius (static loaded radius)
Measurement in inches from the wheel axle centreline to the ground when the tire is properly inflated for the load. Long ton
2,240 Ibs. Also called gross ton.
Low-bed low-boy
A low platform trailer for heavy equipment hauling, usually on 15" diameter tires.
Low pressure tires
Larger cross-section tires for operation at lower pressure. Increased air capacity permits lower pressure.
Low pressure indicator
A unit or combination of units which provides a visible or audible warning signal, whenever the system pressure is below a predetermined value.
Low profile
Refers to the aspect ratio of a tire; section height is smaller than section width.
Lubricate beads
Thorough coating of the beads with a vegetable base lubricant is necessary to prevent bead damage and allow for proper bead seating when mounting a tire. Petroleum base lubricants must never be used.
M + S
Mud and snow tires. Tires having a tread design for maximum traction in mud and snow.New treads (Nu-treads)
A term used by some tire companies to denote a retreaded tire.
Nibbling
The jerking action which occurs in a vehicle, due to the distortion within some tires as they are forced to traverse pavement ridges at a slight angle.
Non-directional tread
An arrangement of bars, grooves and ribs in a manner that gives equal traction in forward or reverse direction.
Nylon
A synthetic fibre.
O Ring
An O-shaped rubber ring used in earthmover tubeless tire mountings to seal air between the loose taper seat and the rim base.
Odometer
(Mileage recording instrument.) A register showing miles driven by a vehicle, usually located in the speedometer.
OEM
Original equipment manufacturer. The term OEM tires refers to tires offered originally by the manufacturer of the vehicle at no extra cost, or the tire selected as an option and mounted by that manufacturer.
Offset
See rim and wheel terms.
Ounce inches
An expression of the force exerted by a heavy spot (or counterbalance weight) on a tire. Multiply the weight times its distance from the axle
centre, i.e.. 3 oz. x 7" = 21 ounce inches.
Out rigger
A device (retractable mechanical legs) used to stabilize equipment such as cranes, ditch diggers, etc., while working.
Outer cap nut
See dual mounting.
Over inflations
Excessive tire pressure in relation to the tire size and load carried.
Over cure
Vulcanizing longer than necessary. Can result in the deterioration of certain physical properties.
Overflow
Spew-out of tread compound at the
mould parting line or at the edge of the matrix skirt which should be trimmed or buffed of f the finished product.
Overload
Carrying more weight on a tire than its listed maximum carrying capacity or, carrying excessive loads on a tire in relation to its inflation (under
inflation).
Oversize
Installing a tire larger than needed to carry the load. A common practice on passenger vehicles to increase one size when replacing OEM (it is not necessarily beneficial).
Over steer
A vehicle tends to turn on a smaller radius than that steered by the driver who finds he is
turning too acutely. An undesirable condition that can be caused by having larger "slip angle. in rear tires than in front tires. Also see tire deviation angle.
Ozone
A faintly blue form of oxygen produced by the silent discharge of electricity into the air.
Ozone checking
The cracking of rubber brought about by continued exposure to ozone in the air which, if extensive, is destructive to a tire.
Ozone compound
(Anti-ozone compound ) - Rubber compounded with certain chemicals to regard ozone damage.
Parallelism, axle
Axles are determined to be parallel, thus minimizing tire wear, if a measurement between two or more axles is equal at both ends of the axle.
Patch
A simple repair unit such as used for a nail hole.
Payload
The actual weight of cargo being carried, including packaging, etc. (GWN - Unladen weight = payload).
Plug repair
The filling of a nail hole by forcing repair material into the damaged area to fill it, often while the tire is mounted and containing air. This not a satisfactory method of repair.
Ply
A layer of parallel cords coated in rubber forming the carcass body, stabilizing plies, etc.
Ply rating
The strength index of a tire. It replaced the old system of marking the actual number of carcass plies in a tire on its sidewall, and is an indication of comparable strength. This system is currently being replaced by the term load range.
Ply separation
A breakdown of bonding compounds causing plies to detach from each other. Usually as a result of excessive heat.
Ply turn up
The extension of a carcass ply to its end after wrapping around the bead.
Pneumatic tire
An air-filled tire. The air carries the load.
Polyester
A synthetic fibre.
Polymer
A material consisting of large units (molecules) made by joining many smaller building blocks (simple molecules). Usually used to describe synthetic rubber.
Power train
Components used in transmission of power from the engine to the wheels.
Pressure build up
Heat causes air to expand resulting in a normal increase in air pressure. Any increase exceeding 15% above starting cold pressure should be investigated. See bleeding.
Probe
A pointed tool, like an ice pick. It is used to determine the extent of injuries during the tire inspection. An awl.
PSI
Pounds per square inch. This is the accepted standard for measuring inflation pressure in a tire.
PTO
Power take-off, used to transmit power from engine to auxiliary equipment.
Puncture
Any penetrating of a tire's air chamber by a foreign object, nail, glass, etc. resulting in loss of air. Such loss can be rapid with the collapse of the
inner tube, or relatively slow in the case of tubeless tires.
Pyrometer
Instrument used to indicate temperature in various areas of the tire.
Quality grading
Department of Transportation requirements for
labelling of various tire safety and performance criteria by the manufacturer.
Radial ply
Refers to the ply or plies used in
tire in which the cords run at right angles to the bead and parallel to the
tire radius.
Radial Run Out
A tire assembly that does not form a
true circle; the radii of the circle are not equal. Most usual causes are
bent wheels (out of round) or tires not mounted properly (beads not seated).
Radius
See loaded radius or free radius.
Radius rods
Metal arms attached to frame and
axles for alignment
Rasp
A tool used to prepare a tire for
section repair and for buffing prior to retreading.
Rayon
A synthetic fibre.
Re-grooving
The act of cutting new tread grooves
into the crown of the tire after the original tread is worn down. A practice
forbidden by many states' laws.
Reinforcement
Any material, usually rubber and
fabric, vulcanized to the tire to return strength to the cord body at an
injury.
Repair gum
See cushion gum
Revolutions per minute (RPM)
The measured revolutions for a tire
travelling one mile.
Reversion
Excessive heating of a cured rubber
compound leading to deterioration of its physical properties.
Rib
The continuous raised portions of
rubber that run circumferentially (straight or in a zigzag pattern) making
up the tread on the tire. Also the term applies to various raised surfaces
circling the sidewall, i.e., guide rib.
Rim pull
Actual amount of effort in pounds
available at point of contact of tire and road surface.
Rim & wheel terms
Measurements, rim:
MEASUREMENTS, WHEEL
SAE
Society of Automotive Engineers.
Safety ledge
A raised area (hump) around the
circumference of the bead seat area of passenger wheels. Its function is to
prevent the tire beads from becoming unseated during hard cornering or while
running with low air pressure. A must with tubeless passenger tires.
Scrap-pile
Discarded tire casings having
service life exhausted through wear or damage.
SDC
Semi-drop centre rim. See rim types.
Secondary failure
The failure which occurs as a result
of a primary failure.
Section height
The vertical measurement from bead
seat to top of crown when mounted, inflated and not under load. (Overall
diameter less nominal rim diameter, divided by two.)
Section repair
Reinforcement made to the casing
when an injury has extended through the tread or sidewall of a tire. The
damaged cord is removed and a new cord is replaced in the form of a repair
unit or patch. (A major repair in the sidewall or tread of a tire. This
repair unit must have cord material for reinforcement, made specifically for
the type tire-bias-ply or radial.)
Section width
The measurement across the tire
width at the widest point when mounted and inflated (not under load),
excluding any decorative mouldings.
Self-cleaning tread
A tread pattern with tapered grooves
and ribs, bars, etc., arranged in a manner that resists packing loose
materials, (mud, etc.) in the grooves.
Self Vulcanising
Vulcanization at room temperature or
above, activated by chemical agents without the application of heat from an
outside source.
Separation
The parting or debonding of any
adjacent parts of the tire (ply to ply, ply to rubber, etc.), usually due to
excessive heat.
Separation solid tires
Rubber pulling away from steel band.
Serial numbers
The individual, consecutive
numbering of tires during production. It may be a combination of letters and
numbers moulded on the sidewall.
Batch number
May be found in addition to a serial number to identify the tire with other tires manufactured during a given period. Set-up
Premature vulcanization of a rubber
compound during processing or storage.
Shelf life
See retread terms.
Shim
Thin metal plates used as spacers in
vehicle alignment.
Shimmy
Side to side movement (or vibration)
of a tire assembly.
Shock absorber
Vibration dampening device used with
chassis springs to lessen road bounce.
Shoulder
Outer edges of tread.
Shredded wire
Short pieces of fine steel wire
mixed into a tread or under tread compound.
Sidewall
That portion of a tire between the
tread and bead.
Single bead
Refers to a tire built with only one
wire bundle in the bead.
Sipe
A hairline groove cut into tread
ribs, bars or blocks to improve traction on wet surfaces.
Skid
To slip, or lose traction, sliding
out from the intended direction. Not to be confused with the terms drift or
sup angle.
Skid depth
(Anti-skid depth) See tread
depth.
Skins
Slang reference to vehicle tires
Skive
To skive; to cut into. Cut away
rubber from an injury in preparation for a section repair.
Sleeve nuts
See dual mountings
Slewed axles
Axles out of parallel.
Slip angle
See tire deviation angle. Soapstone
Lubricant used to prevent sticking
between tire and tube.
Solids
Industrial tires made without an air
chamber.
Spacer
Specific gravity
Weight of given volume of substance
compared to that of an equal volume of water.
Speedometer
Instrument to indicate velocity in
miles per hour.
Special mileage tire
(Re-groovable tire)
A tire manufactured with an extra layer of rubber between the cord body and the original tread design. This extra layer is designed for the purpose of recutting and regrooving, and is specifically labelled as a special mileage commercial tire. Spread axle
Trailer axle, usually six to nine
feet ahead of another axle and located near the centre of the trailer.
Spreader, tire
Any device, manual or hydraulic,
used to spread tire beads for inspection, repair, service, etc.
Spring
Flexible or elastic member
supporting spring weight of vehicle with recovering properties of resuming
to original shape when released after being distorted.
Spring brake
Emergency or auxiliary brake system
utilizing a spring load as a force for braking. May be automatically
actuated by low air pressure or mechanically controlled for use as a parking
brake.
Spring clip
Small metal brackets insuring proper
alignment of spring leaves.
Spring rate
Rate of deflection versus amount of
load applied in other words, how much force is needed to bend a spring a
given distance.
Spring seat
Support on which spring is anchored.
Stabilizer
Device used to stabilize vehicle
during turns sometimes referred to as a sway bar.
Stabilizing plies
Two or more plies of steel,
fibreglass, etc., forming a belt around the circumference of a tire, between
carcass and tread rubber. It reduces tread distortion of radial and bias
belted tires.
Standard rim
A rim that has been calibrated and
found to meet the precise measurements specified by Tire and Rim
Association, Inc. or, where applicable, by European Tire & Rim Association.
Static balance
See balance.
Steering arms
(Tie rod arms)
Arms attached to front axle steering system to effect turn of wheels. Steering axis alignment
See alignment.
Steering axle
An axle that directs control of the
vehicle. It can be powered or non-powered and more than one steering axle
can be present.
Steering knuckle
A steel forging which includes the
wheel spindle. In cars it is the spindle support arm which pivots on ball
joints. In trucks with non-independent front suspension, it pivots on the
kingpin.
Retread (recap)
A means of extending the life off a
tire that has worn its original tread, yet still has a sound carcass. The
casing is prepared by buffing of f tread rubber and vulcanizing new tread
rubber stock in its place. A casing to which tread rubber has been affixed
to extend the useable life of the tire after the original tread has been
worn out.
Retreading terms
· Buff contour
The specked shape of a buffed. · Buff line
The dividing line in the cross section of a tire between the buffed surface of the original tire and the new retread rubber. · Buffered radius
A dimension that ensures the proper contour of the buffed surface according to tire size and type and matrix dimensions. · Buffer
A machine used to rasp the old tread from the tire. · Buffing
Grinding or rasping off remaining tread rubber to give the casing proper texture to accept new retread stock and proper dimensions to fit the matrix. · Buffing template
A machined device of a specific shape used to obtain the required buffed contour. · Builder
A machine used to apply tread rubber to a casing. · Bold-up
The application of retread or repair rubber. · Camelback
Uncured retread rubber in crescent shape, available in various widths and depths according to size and type of tire being retreaded. See die size, below. · Cement
An adhesive compound of rubber and certain chemicals which effect cure, dissolved in rubber solvents. · Chamber
A pressure chamber used to vulcanize pre-cured tread stock to the buffed casing. · Cold cap
So called because the tire is placed in a pressure chamber in a temperature range of 195°-212° until bonding of pre-cured tread rubber is achieved. Also see hot cap. · Cure
Vulcanize uncured rubber through the application of heat, pressure and time to permanently shape and set the rubber to achieve the degree of hardness desired to protect it from the affects of normal operating temperatures and wear. · Curing rim
A special rim that supports the inflated tire during curing process. · Cure tube
A heavy tube within the tire that provides pressure to force the casing against the matrix during the curing process. · Curing gum
A soft, tacky rubber compound used in retreading and repair to facilitate bonding between different rubber compounds and between plies, etc. Also see rubber terms. · Die size
Retread rubber is designated by its crescent shaped dimensions in inches and eighths, and its thickness in 32nds of an inch. (Example: 66-72-16; the crown would measure 6 and 6 eighths, the base 7 and 2 eighths wide; and the thickness 16/32 of an inch, or gauge of the stock rubber.) · Elugger
A machine used to cut the lugs from tires prior to buffing. · Envelope
A thin rubber wrapper that surrounds the tread, sidewall and is tucked inside the curing rim during pre-cured cold process. retreading. It protects bonding materials from humidity within the chamber. · Filler strip
free flowing rubber used under the tread when added thickness is needed. · Full cap
New tread rubber is added to the buffed casing, covering the crown and shoulder areas. · Hot cap
· The conventional method of
retreading in which uncured rubber is added to a buffed casing and cured in
the mould at temperatures of approximately 290°-300°. This temperature
allows uncured rubber to flow in the matrix forming the tread design during
vulcanization.
· Matrix
That portion of the mould which surrounds the tire transferring heat to the uncured rubber and forming the tread pattern. · Mould
A device, that includes a matrix, enclosing the tire and supplying heat and pressure to effect curing. · Peaking
A condition, usually in the cushion rubber resulting from local material starvation and excessive flow from adjacent areas. · Procured tread rubber
Pre-cured rubber, usually of high density and available in various tread designs is lined with cushion gum before applying to a buffed casing using the cold cap method of retreading. Recently it has been applied in some hot cap moulds employing a smooth matrix or other modifications. · Separation
The parting of retread rubber from the buffed casing. · Shelf-life
A time limitation for the storage of uncured retread materials (usually 6 months), beyond which certain properties are lost. Storage of materials in a cool, dark, dry environment insures quality. · Stripping stock
A rubber stock used to extend the wing of tread rubber. · Template (buffing
template)
A pre-cut pattern, usually metal, used to determine the contour of a buffed tire. · Top cap
New tread rubber is added to the buffed casing, covering only the crown area.
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