Tires and Wheels
Dual-Tire Load Capacity Calculator
Estimate total capacity for tires used in dual positions. Use the manufacturer dual-load rating rather than an assumed factor when available.
Set the Dual-Tire Load Capacity assumptions
Each field should describe the same setup, service interval, test, or operating period.
The decision behind the numbers
Estimate total capacity for tires used in dual positions — the equation describes geometry or tire behavior for one defined setup.
Use the manufacturer dual-load rating rather than an assumed factor when available — that condition defines when total dual-tire capacity is comparable with another result.
For a second calculation that will calculate nominal overall tire diameter from metric size markings, use the Tire Diameter.
Sources for the entered values
The Single-tire capacity entry represents rated capacity when one tire is used per side — before calculating, use a measurement or specification from the exact component and operating condition being evaluated.
Dual capacity factor: Per-tire derating or specified dual-load relationship — a compatible entry should use the same loaded condition for every weight and retain the scale ticket or rating source.
For Tires in dual positions, use the quantity described as total tires operating as dual pairs — in the vehicle record, use a measurement or specification from the exact component and operating condition being evaluated.
Measured axle load is defined here as load carried by the dual-tire axle — keeping that definition intact requires you to use the same loaded condition for every weight and retain the scale ticket or rating source.
From measurements to output
In “dual capacity = single capacity × dual factor × number of tires,” the printed units define how each term is interpreted.
No term beyond single-tire capacity, dual capacity factor, tires in dual positions, and measured axle load is introduced in “dual capacity = single capacity × dual factor × number of tires.”
Boundaries of the result
Suspension travel, steering angle, tire growth, body tolerances, and alignment can reveal interference that a static dimension misses — for measured axle load, the page specifically expects load carried by the dual-tire axle.
If your notes raise the question of how to estimate tread wear per 1,000 miles and remaining mileage at the same rate, move to the Tire Tread Wear Rate without changing this page's inputs.
From output to vehicle decision
Total dual-tire capacity answers “Estimate total capacity for tires used in dual positions.” The additional displays, Capacity margin and Load utilization, are a different view of the same entered measurements.
Mismatched inflation, diameter, or wear can overload one tire in a pair — when that condition changes, compare separate calculator runs instead of blending the inputs.
Because use the manufacturer dual-load rating rather than an assumed factor when available, a disagreement between total dual-tire capacity and an outside reference should trigger a review of single-tire capacity and measured axle load.
The current equation stops before the step needed to estimate tire revolutions per mile with an entered loaded-circumference adjustment, which is handled by the Tire Revolutions per Mile.
Common issues with this calculation
What measurement source fits Single-tire capacity when it represents rated capacity when one tire is used per side?
Because single-tire capacity represents rated capacity when one tire is used per side, use a source tied to the exact vehicle, component, and operating period described by the other fields.
How does the warning “Use the manufacturer dual-load rating rather than an assumed factor when available” affect Total dual-tire capacity?
The condition “Use the manufacturer dual-load rating rather than an assumed factor when available” is not corrected automatically by the numeric inputs, so create a separate dual-tire load capacity case when it changes.
What assumption is expressed by “dual capacity = single capacity × dual factor × number of tires”?
In “dual capacity = single capacity × dual factor × number of tires,” single-tire capacity and dual capacity factor are treated as parts of one vehicle case.