Dual Tire Specification Comparator
Compare dual-wheel tire specs: single vs dual load index, load per dual pair and minimum dual spacing for LT and commercial tires.
Compare published spacing and load requirements.
Dual Tire Specification Comparator: Tire Size Inputs
Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.
How Dual Tire Specification Comparator Works?
The Dual Tire Specification Comparator works by reading both numbers of a dual load index, converting each into load capacity and comparing the published minimum dual spacing. The tool uses 4 steps.
Enter the tire marking
Type the size with the dual index, for example LT245/75R17 121/118S.
Split the index
The comparator reads 121 as the single load index and 118 as the dual load index.
Convert to load
The comparator returns 1,450 kg (3,197 lb) single and 1,320 kg (2,910 lb) per tire in dual service.
Check spacing
Enter the tire maker's minimum dual spacing and the wheel's actual dual spacing to confirm clearance between the 2 sidewalls.
Dual Tire Specification Comparator Formula
The Dual Tire Specification Comparator formula for one dual pair is Load_pair = 2 × L(LI_dual).
L_s = L(LI_single)L_d = L(LI_dual)L_pair = 2 × L_dSpacing_actual ≥ Spacing_min- LI_single, LI_dual
- First and second numbers of the load index
- Spacing_min
- Published minimum center-to-center dual spacing (mm)
Worked example
An LT235/85R16 120/116R tire carries 1,400 kg (3,086 lb) single and 1,250 kg (2,756 lb) dual. A dual pair carries 2,500 kg (5,512 lb). A 4-tire dual rear axle carries 5,000 kg (11,023 lb).
Dual Tire Specification Comparator Conversion Table
The Dual Tire Specification Comparator conversion table lists single load, dual load and typical minimum dual spacing for 6 sizes.
| Size | Single load | Dual load per tire | Load per dual pair | Typical min. dual spacing |
|---|---|---|---|---|
| LT215/85R16 115/112Q | 1215 kg (2,679 lb) | 1120 kg (2,469 lb) | 2240 kg (4,938 lb) | 249 mm (9.8 in) |
| LT225/75R16 115/112R | 1215 kg (2,679 lb) | 1120 kg (2,469 lb) | 2240 kg (4,938 lb) | 254 mm (10.0 in) |
| LT235/85R16 120/116R | 1400 kg (3,086 lb) | 1250 kg (2,756 lb) | 2500 kg (5,512 lb) | 272 mm (10.7 in) |
| LT245/75R17 121/118S | 1450 kg (3,197 lb) | 1320 kg (2,910 lb) | 2640 kg (5,820 lb) | 279 mm (11.0 in) |
| LT265/70R17 121/118S | 1450 kg (3,197 lb) | 1320 kg (2,910 lb) | 2640 kg (5,820 lb) | 295 mm (11.6 in) |
| 225/75R16C 121/120R | 1450 kg (3,197 lb) | 1400 kg (3,086 lb) | 2800 kg (6,173 lb) | 254 mm (10.0 in) |
Minimum dual spacing values are representative. The governing value is the one in the tire maker's data book.
What is Dual Tire Specification Comparator?
A Dual Tire Specification Comparator is a tool that compares the single and dual load ratings and dual spacing requirements of tires used in pairs on one axle end. Dually pickups, vans, motorhomes and light commercial trucks run dual rear tires.
A tire in dual service carries less than the same tire in single service. The load drops roughly 5% to 10% to cover uneven load sharing on crowned roads.
Dual tires need a minimum gap between sidewalls. A gap smaller than the published minimum lets the sidewalls rub under load.
What are the uses of Dual Tire Specification Comparator?
There are 4 main uses of the Dual Tire Specification Comparator, including motorhome loading and replacement checks.
Motorhome loading
Confirm the rear dual axle carries the weighed axle load.
Replacement checks
Compare the dual rating of a replacement tire with OE.
Wheel swaps
Confirm new dual wheels keep the minimum spacing.
Fleet specs
Standardize dual-rated tires across a van fleet.
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