Tire & Wheel Encyclopedia
Your complete guide to understanding tires and wheels. Get expert knowledge about components, maintenance, and common issues from the professionals at Los Reyes Tires.
Tire Construction & Anatomy
Understanding the components that make up modern tires
Bead
The inner edge of the tire that sits on the wheel rim, made of high-strength steel wire
Sidewall
The side portion of the tire between the tread and bead, displaying size and rating information
Tread
The outer rubber surface that contacts the road, designed with patterns for traction
Tread Depth
The vertical measurement from the top of the tread to the bottom of the tire's deepest grooves
Shoulder
The outer edges of the tread that connect to the sidewall
Grooves
Deep channels in the tread that help evacuate water and improve traction
Sipes
Small slits in the tread blocks that improve traction, especially in wet or icy conditions
Belt
Steel or fabric layers under the tread that provide strength and stability
Carcass
The tire's structural body made of fabric cord layers called plies
Inner Liner
Airtight rubber layer that prevents air from escaping the tire
Tread Block
Individual rubber segments in the tread pattern separated by grooves
Tread Wear Indicator
Raised bars in the grooves that indicate when tires need replacement (2/32" remaining)
Tire Types & Categories
Different tire designs for various driving conditions and vehicles
All-Season Tire
Versatile tires designed for year-round use in moderate climates with balanced performance
Summer Tire
Performance tires optimized for warm weather with superior dry and wet traction
Winter Tire
Specialized tires with soft rubber compounds and deep treads for snow and ice
All-Terrain Tire (A/T)
Truck/SUV tires designed for both on-road and off-road driving with aggressive tread
Mud-Terrain Tire (M/T)
Heavy-duty off-road tires with large tread blocks for extreme terrain and mud
Performance Tire
High-speed rated tires for sports cars with enhanced handling and cornering
Touring Tire
Passenger tires focused on comfort, quiet ride, and long tread life
Run-Flat Tire
Tires with reinforced sidewalls that can be driven on when deflated for limited distance
Low Profile Tire
Tires with short sidewalls and wide treads for improved handling and appearance
Highway Tire
Truck/SUV tires designed primarily for paved road use with focus on comfort
Tire Specifications & Ratings
Understanding tire size, speed ratings, and performance indicators
Tire Size
Alphanumeric code indicating width, aspect ratio, construction type, and diameter (e.g., 265/70R17)
Aspect Ratio
The ratio of tire height to width, expressed as a percentage in the size designation
Load Index
Numerical code indicating the maximum weight a tire can safely carry
Speed Rating
Letter code indicating the maximum speed a tire can safely maintain (e.g., H=130mph, V=149mph)
UTQG Rating
Uniform Tire Quality Grade rating for treadwear, traction, and temperature resistance
Treadwear Rating
UTQG number indicating expected tire life (higher numbers = longer lasting)
DOT Number
Department of Transportation code including manufacturing date and plant location
Ply Rating
Indicates tire strength and load capacity, especially important for truck tires
Max Inflation Pressure
Maximum air pressure (PSI) a tire can safely hold, marked on sidewall
Load Range
Letter designation (C, D, E, etc.) indicating tire's load-carrying capacity
Wheel Components
Parts and features of automotive wheels and rims
Wheel Rim
The outer edge of the wheel where the tire bead seats
Wheel Diameter
The size of the wheel measured from bead seat to bead seat (e.g., 17", 20")
Wheel Width
The distance between the inner and outer bead seats
Offset
Distance from the wheel's mounting surface to its centerline (positive, negative, or zero)
Backspacing
Distance from the mounting surface to the inner edge of the wheel
Bolt Pattern (PCD)
Number of lug holes and diameter of the circle they form (e.g., 5x114.3)
Center Bore
The diameter of the center hole that fits over the vehicle's hub
Hub-Centric
Wheels designed to fit snugly on the vehicle hub for proper centering
Lug-Centric
Wheels centered by lug nuts rather than the hub
Valve Stem
The inflation valve where air is added or released from the tire
Bead Lock
Off-road wheel feature that mechanically clamps the tire bead to prevent separation
Wheel Finishes & Materials
Types of wheel coatings, materials, and appearance options
Alloy Wheel
Wheels made from aluminum or magnesium alloys, lighter and stronger than steel
Steel Wheel
Traditional wheels made from stamped steel, durable and economical
Forged Wheel
Wheels made by forging aluminum under high pressure for maximum strength and light weight
Cast Wheel
Wheels made by pouring molten aluminum into molds, most common manufacturing method
Chrome Plating
Shiny metallic finish applied through electroplating for mirror-like appearance
Powder Coating
Durable finish applied as dry powder then baked on, available in many colors
Painted Finish
Liquid paint finish, often with clear coat protection
Machined Finish
Finish created by cutting the wheel face with a lathe for bright metal appearance
Matte Black
Non-reflective black finish popular for aggressive, modern look
Polished Finish
Mirror-like aluminum finish achieved through mechanical polishing
Hyper Silver
Dark silver metallic finish with hints of charcoal
Tire Maintenance & Service
Essential tire care procedures and services
Tire Rotation
Moving tires to different positions on vehicle to ensure even wear
Wheel Balancing
Adding weights to wheels to eliminate vibration caused by uneven weight distribution
Wheel Alignment
Adjusting suspension angles to ensure proper tire contact with road
Tire Pressure
Amount of air in tire measured in PSI, critical for safety and performance
TPMS
Tire Pressure Monitoring System that alerts driver to low tire pressure
TPMS Sensor
Electronic sensor inside tire that monitors air pressure and temperature
Tire Mounting
Installing a tire onto a wheel using specialized equipment
Tire Dismounting
Removing a tire from a wheel
Bead Seating
Process of inflating tire to properly seat the bead against the rim
Tire Patch
Internal repair of punctured tire using plug and patch combination
Tire Plug
Temporary external repair of small puncture in tire tread
Nitrogen Fill
Inflating tires with nitrogen gas instead of air for improved pressure retention
Tire Problems & Wear Patterns
Common tire issues, symptoms, and their causes
Cupping
Scalloped wear pattern caused by worn suspension, imbalance, or misalignment
Feathering
Wear where tread ribs are smooth on one side and sharp on the other, indicates alignment issues
Center Wear
Excessive wear in center of tread caused by over-inflation
Edge Wear
Excessive wear on outer edges caused by under-inflation or aggressive cornering
Camber Wear
One-sided wear caused by improper camber alignment angle
Toe Wear
Rapid wear on inner or outer edges caused by incorrect toe alignment
Flat Spot
Worn flat area on tire caused by hard braking or skidding
Bubbles/Bulges
Bulge in sidewall caused by impact damage to internal structure
Dry Rot
Cracking in rubber caused by age, UV exposure, and lack of use
Puncture
Hole in tire caused by nail, screw, or sharp object
Blowout
Sudden loss of air pressure due to tire failure, often catastrophic
Slow Leak
Gradual air loss requiring frequent inflation, often from small puncture or valve issue
Performance & Specialty
Advanced tire and wheel concepts for performance applications
Staggered Fitment
Using wider wheels/tires on rear axle than front for improved traction
Plus Sizing
Installing larger diameter wheels with lower profile tires while maintaining overall diameter
Tire Compound
Rubber formula affecting grip, wear, and temperature performance
Tread Pattern
Design of grooves and blocks optimized for specific conditions (symmetric, asymmetric, directional)
Directional Tread
Tread pattern designed to rotate in one direction only for optimal water evacuation
Asymmetric Tread
Different tread patterns on inside and outside for varied performance characteristics
Hydroplaning
Loss of traction when water separates tire from road surface
Contact Patch
The area of tire actually touching the road at any given moment
Sidewall Height
Vertical height of tire sidewall, affects ride comfort and handling
Wheel Spacer
Device installed between wheel and hub to push wheel outward for wider stance
Tire Shaving
Machining tread to reduce depth for racing or AWD applications
Have Questions About Your Tires or Wheels?
Our expert team at Los Reyes Tires is here to help. Family owned since 2005, serving San Diego with pride.
