BFG Tire Pressure Calculator
Calculate the ideal PSI for your BFGoodrich KO2, KM3, or Trail-Terrain tires based on load adjustments.
Select the tire type originally listed on your vehicle’s door placard.
The pressure recommended by the vehicle manufacturer (usually found on the driver door jamb).
Please enter a valid pressure between 10 and 100 PSI.
Found on your original tire (e.g., 265/70R17 112T).
The load index of your new BFGoodrich tires (e.g., 121 for Load Range E).
45 PSI
Formula: This bfg tire pressure calculator uses the TRA (Tire and Rim Association) load-inflation tables methodology. When converting from P-metric to LT-metric, we apply a 1.10 load reduction factor to the P-metric rating and solve for the equivalent pressure in the LT load curve.
Load Capacity vs. Tire Pressure
Comparison of load carrying capacity (lbs) between OEM and New BFG Tires.
| Pressure (PSI) | OEM Tire Load (lbs) | New BFG Load (lbs) | Status |
|---|
What is a BFG Tire Pressure Calculator?
A bfg tire pressure calculator is a specialized tool used by truck, SUV, and off-road enthusiasts to determine the correct air pressure when upgrading from factory tires to BFGoodrich All-Terrain (KO2) or Mud-Terrain (KM3) tires. Most vehicles come from the factory with P-metric (Passenger) tires, while BFG’s flagship off-road tires are often LT-metric (Light Truck). Because these tire types have different internal constructions and air volume capacities, simply following the door placard PSI can lead to premature wear or dangerous handling.
Using a bfg tire pressure calculator ensures that your new tires maintain the same load-carrying capacity as the original equipment (OEM). If you run LT tires at the low pressures designed for P-metric tires, the tires will be overloaded, causing excessive heat buildup and potential sidewall failure. Conversely, over-inflating can lead to a harsh ride and a “crowned” tread pattern that wears out the center of the tire prematurely.
BFG Tire Pressure Calculator Formula and Mathematical Explanation
The mathematical foundation of the bfg tire pressure calculator relies on the Load-Inflation curves established by the Tire and Rim Association (TRA). The goal is to find the pressure where the New Tire Load Capacity is greater than or equal to the OEM Load Capacity.
The derivation follows these steps:
- Determine OEM Load: If the OEM tire is P-metric on a Light Truck/SUV, the load capacity at the placard PSI is divided by 1.10.
- Identify Target Load: This “derated” load becomes the minimum weight each new tire must support.
- Inverse Load Calculation: We solve for Pressure (P) using the LT load-inflation power formula: Load = k * P^0.7.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| OEM PSI | Factory Recommended Pressure | PSI | 30 – 45 |
| Load Index (LI) | Maximum weight capacity code | Numeric | 90 – 126 |
| Derating Factor | Safety adjustment for P-metric on trucks | Multiplier | 1.10 |
| Service Description | Combination of LI and Speed Rating | Alpha-Numeric | 121R, 115S |
Practical Examples (Real-World Use Cases)
Example 1: Toyota Tacoma Upgrade
An owner replaces factory P265/70R16 tires (Load Index 112, 30 PSI placard) with LT265/75R16 BFG KO2 tires (Load Index 123). The bfg tire pressure calculator calculates the original load capacity (~2100 lbs) and determines that the LT tires require 41 PSI to safely carry the same weight. Using the factory 30 PSI would result in an under-inflated, unsafe condition.
Example 2: Heavy Duty Towing
A Ford F-250 owner upgrades to larger 37-inch BFG KM3 tires. Even though the new tire is larger, the bfg tire pressure calculator might show a required street pressure of 50 PSI, whereas the max sidewall pressure is 65 PSI. This allows the user to balance comfort with the towing capacity calc requirements of the vehicle.
How to Use This BFG Tire Pressure Calculator
- Check your Door Placard: Open the driver’s door and find the sticker listing the original tire size and recommended cold inflation pressure.
- Identify OEM Load Index: Find the load index of the tires that came with the vehicle (e.g., 112).
- Enter New Tire Specs: Look at the sidewall of your new BFG tires to find their Load Index (e.g., 121).
- Review the Primary Result: The calculator will highlight the recommended street PSI.
- Adjust for Off-Road: Remember that this result is for street use. For off-road, use the results from an off-road guide to safely air down.
Key Factors That Affect BFG Tire Pressure Results
- Tire Volume: Larger tires (35s, 37s) often require less pressure to carry the same load than smaller tires because the larger air volume does more of the work.
- Load Range: BFG tires come in Load Range C, D, and E. E-rated tires have stiffer sidewalls and typically require higher pressures for stability.
- Vehicle Weight: If you have added heavy steel bumpers, winches, or roof racks, you must adjust the bfg tire pressure calculator inputs to reflect your higher Gross Vehicle Weight.
- Ambient Temperature: For every 10°F change in temperature, tire pressure changes by approximately 1 PSI.
- Altitude: High-altitude driving can affect the pressure differential between the inside and outside of the tire.
- Rim Width: Mounting a tire on a rim that is too narrow or too wide can distort the contact patch, requiring a bfg tire pressure calculator adjustment to maintain a flat footprint.
Frequently Asked Questions (FAQ)
Related Tools and Internal Resources
- Tire Size Calculator – Compare physical dimensions of old vs. new tires.
- Load Index Chart – Comprehensive list of weight ratings for all tire codes.
- Off-Road Guide – Learn how to safely air down for sand, rocks, and mud.
- TPMS Reset Guide – How to recalibrate your sensors for new pressure settings.
- Towing Capacity Calc – Determine if your new tires can handle your trailer tongue weight.
- Speedometer Correction – Adjust your ECU for larger BFG tire diameters.