Glossary

AG TIRE DEFINITIONS

A
Aspect Ratio refers to height of sidewall as a percentage of section width. i.e. On 900/50R46, 50 aspect ratio = 50% of 900 mm = 450 mm sidewall height.

B
Bias Construction means bias ply cords extend diagonally from bead to bead on tire.

C
Casing is supporting structure of tire or body beneath tread and sidewalls consisting of plies (Bias or Radial) anchored to bead.
Carrying Capacity is how much weight a tire is designed to carry at a specific air pressure.
Cold Inflation Pressure is amount of air pressure in tire before it has built up heat from use, measured in PSI (Pounds per Square Inch).
Compound is particular blend of rubber and raw materials enabling desired performance characteristic of tire.
Contact Patch is area of tire in contact with ground, also called footprint.
Cross Section is section width from inner sidewall to outer sidewall.
Cyclical Field Operation, or CFO, is tire specifically designed to carry more load than conventional radial tires of same size, designed to meet demands of extreme load cycles common at harvest.

D
Deflection is deformation of tire at point of contact with ground.
Directional Tread is tire designed to rotate in one direction.
DOT Mark is stamp on sidewall of tire noting it is approved for highway service in accordance with U.S. Department of Transportation guidelines.
Duals are two tires mounted on each side of axle.
Durometer is tool used to measure hardness of tire compound.

F
Field Hazard is cut, snag, or puncture that renders tire unserviceable, not caused by manufacturer defect.
Flotation defines tires with wider section widths than standard, designed to improve traction, reduce soil compaction, in some cases enabling equipment to operate in wet mucky conditions.
Footprint is surface area of tire in contact with the ground.
Free Radius is radius of tire not deflected under load.
Free Replacement means tire will be replaced free of charge if in accordance with specific particulars of warranty.

G
Group refers to a specific set of sizes with virtually identical overall diameters, but varying widths, categorized in accordance with Rolling Circumference Index (RCI) Chart.
Gross Flat Plate is surface area of tire in contact with ground.

H
High Angle Lug denotes R-1 tread with superior road performance, rider comfort, and long wear relative to low angle lug.

I
IF is abbreviation for Improved Flexion. Tire can carry 20% more load than standard tire at same air pressure.
International Load Index Chart states International Load Index Number and corresponding weight carrying capacity.

K
Kilopascal or kPa is metric unit for air pressure, with 1 PSI = 6.9 kPa.

L
Lateral Runout indicates wobble or deviation of tire sidewall from perfect parallel plane.
Load Carrying Capacity is amount of weight tire is certified to carry at specified air pressure.
Load Index is assigned number from 0 to 279 equating to load carrying capacity of tire.
Long Bar Short Bar Lug is tread pattern with combination one bar short / one bar long lug design touted to reduce vibration in field; however, falling out of favor with engineers and new production.
Low Angle Lug denotes R-1 tread with superior traction relative to high angle lug.

M
Metric Size is latest version of size markings providing cross section in millimeters, aspect ratio, along with rim diameter in inches (i.e. 480/80R42), whereas older Standard Size Ag Tire Markings consist of section width in inches and rim diameter in inches (i.e. 18.4R42).
Multi-Angle Lug is combination of low angle and high angle, providing combination of good traction, road performance, rider comfort, and long wear.

O
Overall Diameter is diameter of inflated tire without load.

P
PSI is abbreviation for pounds per square inch, measuring air pressure in tire.
Ply is rubber coated layer of fabric containing cords that run parallel to each other that make up casing.
Ply Rating identifies how much load tire can carry at industry specified air pressure.
Pneumatic designates tire designed to be filled with air.
Power Hop is bouncing of tractor usually under high draw bar pull, created by tire gaining traction as sidewall flexes and recoils.
Pro Rated usually describes tire warranty adjustment claim where customer is credited back portion of purchase price, taking into consideration tire wear and age.

R
Radial is tire produced with radial cords extending at right angles from bead to bead across tread that “radiate” from imaginary center of wheel, allowing tread to act independent of sidewall, resulting in larger footprint compared to Bias.
Radial Runout indicates deviation of tire or wheel roundness relative to perfect circle.
Road Lope is bouncing or swaying of Ag Equipment during road transport, often caused by incorrect air pressure, sidewall flex, or excessive radial runout.
Rolling Circumference is linear distance traveled by tire in one circumferential revolution.
Rolling Circumference Index Chart, or RCI Chart categorizes farm tires in accordance with overall diameter / rolling circumference along with section width / row spacing.
Rolling Circumference Index or RCI refers to group of tires with varying section widths and rim diameters that have virtually same rolling circumference / overall diameter.

S
Section Width, same as cross section, measures tires width from inner sidewall to outer sidewall without load.
Series is same as aspect ratio (i.e. 320/85R34 is an 85 series tire).
Sidewall Height is tire’s sidewall height from rim to tread.
Singles is one tire mounted on each side of axle.
Shoulder is area of tire where sidewall and tread meet.
Soil Compaction describes soil particles pressed together caused by heavy field equipment thru tire pressure.
Speed Rating designates maximum speed rating of tire in accordance with Alphabetical Speed Rating Chart (A-Z), under specified load and service conditions.
Standard Size Ag Tire Markings consist of section width in inches and rim diameter in inches (18.4R42), whereas newer Metric Markings provide cross section in millimeters, aspect ratio, along with rim diameter in inches (480/80R42).
Static Loaded Radius or Loaded Radius is distance from centerline of axle to ground under prescribed load and air pressure at rest.
Star Rating is designation related to a standard maximum air pressure. *=18 PSI, **=24 PSI, ***= 30 PSI, with maximum load varying by size.  Star rating system is falling out of favor, with Ag Tire manufacturers preferring to use International Load Index Chart.
Steel Belt is strip or belt placed under tread rubber and over casing, consisting of multiple steel cords covered in rubber, designed to reduce punctures and improve uniformity.
Stubble is short stiff stalks of grain or hay remaining after harvest.
Stubble Damage refers to severe abrasions and scarring of tire caused by field stubble.

T
TIN or Tire Identification Number is same as Serial Number or DOT if approved for highway service. Indicates plant, size, tire type or brand, and date of manufacture.
Triples are three tires mounted on each side of axle
Traction is grip, or friction between tire and soil.
Tread is portion of tire that comes in contact with soil, distinguished by lugs, grooves, or other various designs.
Tread Width is breadth of tire tread.

V
VF is the abbreviation for Very High Flexion. Tire can carry 40% more load than standard tire at same air pressure.
Vulcanization is heating rubber under pressure to improve resilience and strength.

All information is provided in this blog solely to provoke thought.  All deductions made from information on this site must be confirmed by Certified Ag Tire Dealer before use.  Ag Tire Talk does not recommend anyone conduct tire service work with exception of Certified Ag Tire Dealer Professionals.