Tire load capacity and load index
Does a load index prove that a tire is suitable for a vehicle?
No. A load index maps a code to a reference mass under the applicable test and application conditions; it does not by itself approve a tire for a vehicle. Start with the exact front and rear service descriptions in the vehicle label and handbook, then check the maximum loaded axle ratings, wheel limits, single or dual use, speed symbol, construction and the exact tire maker’s load-and-inflation data. Do not choose a tire from GVWR divided by four or from a universal pressure percentage.
Try a load index
Type the number printed before the speed letter, such as 91V or 94W.
- kg per tire
- 615
- lb per tire
- 1,356
Reference-table value only. Always match your vehicle placard and tire sidewall markings.
Reviewed sources
The UN annex tables support the index-to-mass values, while NHTSA supports vehicle-label size and cold-pressure checks. These sources do not create a universal pressure/capacity curve or vehicle approval.
- UN Regulation No. 30: passenger-car tire load-index tables (EUR-Lex)
- UN Regulation No. 54: commercial-tire load-index tables (EUR-Lex)
- NHTSA TireWise tire selection, loading and pressure guidance
Checked:
What the load index does and does not say
The lookup converts a published index into kilograms per tire. That value is useful for decoding and comparison, but it is not a complete fitment specification. The same nominal size can have different service descriptions, constructions or application limits, and a numerically higher index does not permit exceeding any vehicle, axle, wheel, hitch or tire limit.
Load-capacity verification workflow
| Step | Verify | Decision |
|---|---|---|
| Identify the approved setup | Exact tire size, load index, speed symbol, construction and any front/rear or axle-specific requirement in the label and handbook. | Treat missing or conflicting information as unresolved, not as permission to estimate. |
| Read vehicle and axle limits | Maximum loaded vehicle and axle ratings, payload label, towing limits and wheel specifications. | Keep each limit separate; the lowest applicable limit controls. |
| Confirm the real application | Actual occupants, cargo, accessories, hitch load, axle distribution and single or dual mounting. | Measure loaded axle weights where the maker, conversion or use case requires confirmation. |
| Match the exact tire data | Product data sheet for the exact size, service description, load range and single/dual application. | Use the tire maker’s table; do not transfer a percentage or pressure from another tire. |
| Apply the specified cold pressure | Vehicle label/handbook value for that approved setup and load state, or exact maker instruction where applicable. | The sidewall maximum and an absent TPMS warning are not pressure-setting methods. |
| Resolve every mismatch | Lower index, different construction, alternate size, changed wheel, conversion, unusual load or missing documentation. | Obtain vehicle- and tire-maker confirmation or qualified professional review before use. |
Pressure and capacity are tire-specific
Inflation affects how a pneumatic tire carries load, but there is no safe universal bar-to-percentage table across SL, XL, LT, commercial and other constructions. A pressure above one reference point does not automatically add capacity, and a lower pressure cannot be cleared for “light use” by a generic percentage. Use the exact load-and-inflation table and never exceed component limits.
SL, XL, reinforced and LT are not interchangeable labels
Construction markings and load range change the applicable data and operating envelope. XL does not mean every tire carries a fixed percentage more or uses one common pressure. Match the complete approved service description; a higher sidewall number cannot repair a construction or fitment mismatch.
Do not divide total vehicle mass equally by four
Front and rear axle loads are rarely guaranteed equal, and towing, cargo, conversions and accessories can change their distribution. A GVWR division can hide an overloaded axle or individual position. Use manufacturer axle ratings and, when needed, actual loaded axle measurements while preserving the approved tire specification.
Single and dual ratings are separate data
A commercial tire may publish distinct single and dual capacities. Do not create a dual rating by applying one percentage to a single rating, and do not assume the number of tires alone increases the legal or mechanical axle limit. Spacing, wheel, pressure, matching and maker requirements still apply.
Visible appearance cannot confirm spare capacity
Bulging, heat, vibration, repeated pressure loss, damage or unstable handling require unloading and inspection, but their absence does not prove the load is acceptable. After suspected overloading or underinflation, correct pressure alone cannot exclude hidden internal damage.
Limits of this guide
This page decodes load index and explains a verification process. It does not approve a replacement tire, calculate vehicle payload or publish a universal load-and-inflation table. Exact vehicle, tire, wheel, axle, speed, temperature and jurisdiction requirements remain controlling.
Related checks: load index reference, tire overloading, heavy-load pressure.
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tires are worn or the replacement size changes diameter.