Wheels and tires are the single most impactful modification you can make to your truck or Jeep. They affect everything: capability, appearance, ride quality, fuel economy, and handling. Getting this right matters.
This guide covers everything you need to know before upgrading, from understanding tire sizing to selecting the right wheel specs for your build.
Understanding Tire Sizing
Tire sizes can be confusing. Let's decode them:
Metric Sizing (P-Metric)
Example: 265/70R17
- 265: Tire width in millimeters
- 70: Aspect ratio (sidewall height as % of width)
- R: Radial construction
- 17: Wheel diameter in inches
To calculate overall diameter: Width × (Aspect Ratio/100) × 2 + (Wheel Size × 25.4)
For 265/70R17: 265 × 0.70 × 2 + (17 × 25.4) = 371 + 432 = 803mm ≈ 31.6 inches
Flotation/LT Sizing
Example: 35x12.50R17
- 35: Overall tire diameter in inches
- 12.50: Tire width in inches
- R: Radial construction
- 17: Wheel diameter in inches
This system is simpler for off-road tires, the first number is the diameter.
Common Tire Sizes by Application
Stock-ish (31-33")
- 265/70R17: ~31.6" (common stock size)
- 275/70R17: ~32.2"
- 285/70R17: ~32.7"
- 33x12.50R17: 33"
Good for: Leveled or stock trucks, daily drivers wanting mild improvement
Mid-Size (34-35")
- 295/70R17: ~33.3"
- 315/70R17: ~34.4"
- 35x12.50R17: 35"
Good for: 2.5-4" lifts, balanced builds, serious capability improvement
Large (37"+)
- 37x12.50R17: 37"
- 40x13.50R17: 40"
Good for: Dedicated off-road rigs, 4"+ lifts, regearing required
Understanding Wheel Sizing
Wheel specs are just as important as tire sizing. Here's what matters:
Diameter and Width
Example: 17x9
- 17: Wheel diameter in inches (must match tire)
- 9: Wheel width in inches
Wheel width should match your tire width. General guidelines:
- 10.5-11.5" tire width → 8-9" wheel
- 12.5" tire width → 9-10" wheel
- 13.5" tire width → 10-11" wheel
Wider wheels stretch the tire for a different look; narrower wheels provide more sidewall protection for off-road use.
Offset
Offset is the distance from the wheel's mounting surface to the centerline, measured in millimeters.
- Positive offset (+): Mounting surface toward the outside (wheels tucked in)
- Zero offset (0): Mounting surface at centerline
- Negative offset (-): Mounting surface toward the inside (wheels pushed out)
Stock truck wheels typically have positive offset (+15 to +44mm). Aftermarket wheels often have less positive or negative offset for a wider stance.
Impact of offset changes:
- More negative offset = wider stance = more stress on wheel bearings and steering
- Too much poke requires fender trimming or flares
- Stock offset maintains factory handling and wear characteristics
Backspacing
Backspacing is the distance from the back of the wheel to the mounting surface. It's related to offset but measured differently.
Higher backspacing = wheel sits more inward
Lower backspacing = wheel sits more outward
For clearance with suspension components, brake calipers, and steering, backspacing matters. Many lifted trucks need lower backspacing to clear new suspension geometry.
Bolt Pattern
Wheels must match your vehicle's bolt pattern. Common patterns:
- 5x5 (5x127mm): Jeep JK, JL, JT
- 6x5.5 (6x139.7mm): Many trucks (GM, Toyota)
- 6x135mm: Ford F-150
- 8x6.5 (8x165.1mm): Heavy-duty trucks
- 8x170mm: Ford Super Duty
Tire Types Explained
All-Terrain (A/T)
The jack-of-all-trades tire:
- Reasonable on-road manners and noise
- Capable in light-to-moderate off-road conditions
- Good wet weather performance
- Decent tread life (40,000-60,000 miles)
- Good for daily drivers that see occasional dirt
Popular options: BFG KO2, Toyo AT3, Falken Wildpeak AT3W, Nitto Ridge Grappler
Mud-Terrain (M/T)
Aggressive tread for serious off-road:
- Excellent in mud, rocks, sand
- More road noise than A/T
- Shorter tread life (25,000-40,000 miles)
- Reduced wet weather grip
- Best for vehicles that see regular off-road use
Popular options: BFG KM3, Nitto Trail Grappler, Toyo MT, Mickey Thompson Baja Boss
Highway/All-Season
On-road focused with mild off-road capability:
- Quiet and comfortable
- Long tread life (50,000-70,000 miles)
- Good fuel economy
- Limited off-road grip
- Best for road-focused trucks
Hybrid/Rugged Terrain
Between A/T and M/T:
- More aggressive than A/T, less than M/T
- Better on-road behavior than M/T
- Good all-around capability
Popular options: Nitto Ridge Grappler, Toyo RT, General Grabber X3
Load Ratings and Ply
Load ratings matter, especially for trucks:
Load Ratings
- SL (Standard Load): Light duty, passenger vehicles
- XL (Extra Load): Higher capacity passenger tires
- C Load Range: 6-ply equivalent, light truck
- D Load Range: 8-ply equivalent, medium truck
- E Load Range: 10-ply equivalent, heavy truck
- F Load Range: 12-ply equivalent, commercial
Higher load ratings support more weight but have stiffer sidewalls, affecting ride quality. Match load rating to your actual use, you don't need E-rated tires on a half-ton that never tows.
Load Index
The load index number (like 121) indicates maximum weight capacity:
- 116 = 2,756 lbs per tire
- 121 = 3,197 lbs per tire
- 126 = 3,748 lbs per tire
Your total load capacity should exceed your vehicle's GVWR.
Fitment Considerations
Before buying, ensure everything fits:
Fender Clearance
- Measure from fender to highest point of current tire
- Account for suspension compression and turning
- May need trimming, lifting, or fender flares
Inner Fender/Frame Clearance
- Check clearance at full steering lock
- Account for suspension travel
- More negative offset = less inner clearance
Brake Caliper Clearance
- Aftermarket wheels may not clear factory calipers
- Big brake kits need specific wheel specs
- Check manufacturer specs before buying
Speedometer Calibration
Larger tires affect speedometer accuracy:
- 33" tires on a truck calibrated for 31" = speedometer reads low
- At indicated 70 mph, you might actually be doing 75+
- Recalibration via programmer or shop required
Gear Ratio Considerations
Larger tires effectively change your gear ratio:
- Engine revs lower at highway speeds (feels sluggish)
- Transmission hunts for gears
- Fuel economy drops
- Regearing compensates but costs $1,500-3,000+
General rule: Going up more than 10-15% in tire diameter often benefits from regearing.
Wheel Material: Steel vs Alloy
Steel Wheels
- Cheaper ($80-150 per wheel)
- Heavier (more unsprung weight)
- More durable against impacts
- Easier to repair if bent
- Limited style options
- Best for: Budget builds, dedicated off-road use
Alloy Wheels
- More expensive ($150-500+ per wheel)
- Lighter weight (better performance and fuel economy)
- More style options
- Can crack under severe impact
- Better heat dissipation for brakes
- Best for: Daily drivers, balanced builds
Forged vs Cast
Alloy wheels come in cast and forged varieties:
- Cast: Molten aluminum poured into molds. Affordable, adequate for most use.
- Forged: Aluminum compressed under extreme pressure. Stronger, lighter, much more expensive.
Beadlock Wheels
Beadlocks clamp the tire bead to prevent it from separating at low air pressures:
- Required for serious rock crawling at very low PSI (under 10 psi)
- Heavier than standard wheels
- Require regular maintenance (bolt torque checks)
- Not street legal in many states (non-DOT)
- DOT-approved beadlocks exist but are pricey
Most wheelers don't need true beadlocks unless running single-digit PSI regularly.
The Upgrade Process
Here's how to approach a wheel and tire upgrade:
1. Define Your Goals
- What's the primary use? (daily driving, off-road, towing)
- What look are you going for?
- What's your budget?
2. Research Fitment
- Check forums for your specific vehicle
- Use fitment galleries to see what others run
- Consult with local shops experienced with your platform
3. Choose Tire Size and Type
- Start with size based on your lift/clearance
- Select tire type based on use
- Research specific models for reviews
4. Choose Wheel Specs
- Match diameter to tire
- Select width appropriate for tire
- Choose offset/backspacing for stance and clearance
- Verify bolt pattern
5. Purchase and Install
- Buy from reputable dealers
- Have a shop mount and balance
- Get an alignment after installation
- Calibrate speedometer
The Bottom Line
Wheels and tires are the foundation of any build. Understanding sizing, fitment, and your actual needs prevents expensive mistakes. Start with your goals, research your specific vehicle, and choose quality components that match your use case.
The right wheel and tire combo transforms your truck or Jeep. The wrong one creates problems. Take the time to get it right.