Identify headings and units in tire load-inflation tables

The short answer

A tire load-inflation table is a grid: one axis lists inflation pressures, the other lists tires (by size or load index), and each cell gives the load the tire can carry at that pressure. Before you read any cell, confirm six things from the headings and footnotes. First, the tire category the table covers, such as standard-load passenger, Reinforced/XL passenger, or van/light truck. Second, the exact tire size. Third, the service description, which is the load index plus speed symbol, such as 91V. Fourth, the load classification exactly as printed: ply rating (PR), lettered Load Range, or Reinforced/XL. Fifth, whether the figure applies to single or twin (dual) fitment. Sixth, the units and basis: bar, kPa or psi for pressure; kilograms or pounds for load; and whether the load is per tire or per axle.

If any of these does not match your tire, the number you read belongs to a different tire. The same load index at the same pressure can carry a different load in a different category table.

Key terms you will see in the headings

• Load index (LI): a numeric code for a tire's maximum load capacity under the conditions the table defines. It appears in the service description on the sidewall, such as the 91 in 91V.
• Speed symbol: the letter after the load index. Some tables set speed limits for the loads they list, so read it alongside the load index.
• Service description: the load index and speed symbol together.
• PR (ply rating): a load-strength designation. Some tables use it instead of a letter.
• Load Range: a lettered load-strength designation used in many North American light-truck tables. It is a separate heading from PR. Do not assume one converts to the other unless the publication says so.
• Reinforced / XL (Extra Load): passenger tires built to run at higher pressures than standard-load tires. They usually have their own table.
• Single / twin (dual) fitment: single means one tire at each end of an axle. Twin means two tires mounted side by side at each end, common on the rear axle of vans and light trucks.
• Cold inflation pressure: pressure measured before the tire has been warmed by driving. Load tables are normally built on cold pressure.

How to recognize each heading on the page

Manufacturer technical databooks, often distributed as PDFs, illustrate how layouts differ. Continental's 2015–2016 technical databook is a useful dated example because it uses two distinct layouts.

Van tables (pages 76–87 of that edition) run across two-page spreads. The left side identifies the tire: size, PR and service description. The right side holds load-index, wheel-position and pressure columns. The load columns report kilograms per axle at a given pressure in bar. Note that the classification heading is PR, not a lettered Load Range. Record it as PR.

Those van spreads often show two load indices separated by a slash. The book's footnotes (page 125) define the first as the single-fitment index and the second as the twin-fitment index. They also define the S and T markers as single and twin fitment. A slash pair such as 109/107, used here only as an illustrative format, is two different ratings. You need the footnote to know which applies to your wheel position.

Passenger-car tables in the same book (pages 104–106) are organized differently. Rows are load indices, columns are pressures in bar, and cells are capacities in kilograms. There is one table per category: Table 1 for standard load and Table 2 for Reinforced/XL. Table 1 also states speed and camber conditions for its values (page 104). The book separately defines its pressures as cold gauge pressure (page 9). These conditions sit in titles, notes and front matter, not in the column headings, so read the surrounding text as well as the grid.

Look-alikes that cause misreadings

• Standard-load vs. XL tables: they can share the same load-index rows and pressure columns. Only the table title tells them apart.
• Per-tire vs. per-axle loads: an axle figure is far larger than a single-tire figure. Check the capacity heading or footnote for the basis.
• Single vs. twin values: paired indices, or S/T columns, give two answers for the same tire.
• PR vs. Load Range: both describe load strength but are printed differently. If the table shows only one, record that one and mark the other as not shown.
• Unit mix-ups: bar, kPa and psi columns look similar at a glance. 2.2 bar is 220 kPa and about 32 psi.

Why the category heading matters: a worked illustration

In the Continental passenger tables, load index 91 at 2.2 bar shows 555 kg in Table 1 (standard load) and 495 kg in Table 2 (Reinforced/XL). Same index, same pressure, different category, different entry. The values convert to about 1,224 lb and 1,091 lb (1 kg ≈ 2.2046 lb), and 2.2 bar is about 31.9 psi (1 bar ≈ 14.504 psi). This example shows why you must identify the table first. It is not a pressure recommendation for any tire or vehicle.

Step-by-step: reading a table entry correctly

• 1. Note the publisher, edition or date, and page. Tables are revised, and a dated databook only reflects its own edition.
• 2. Identify the tire category from the table title, such as standard-load passenger, Reinforced/XL or van/light truck. Compare it with your sidewall markings.
• 3. Find your exact tire size in the table, or the load-index row if the table is organized by index.
• 4. Confirm the service description and copy the load index and speed symbol exactly.
• 5. Copy the load classification exactly as printed (PR, Load Range or XL). If it is absent, write "not shown". Do not invent an equivalent.
• 6. Determine single or twin fitment from paired indices, S/T markers or wheel-position columns, and confirm the meaning in the footnotes.
• 7. Read the pressure heading for units and basis, such as bar, kPa or psi, and cold pressure.
• 8. Read the capacity heading for units and basis: kg or lb, per tire or per axle.
• 9. Trace the row to the column for the pressure in question and record the cell value.
• 10. Attach any footnotes and table conditions, such as speed or camber limits, to the recorded entry.
• Completion check: you have read the right entry only if category, size, service description, classification, fitment, pressure units and load basis all match your tire and are recorded together with the value.

A worksheet for recording what you read

Field	What to record
Document / page	Publisher, edition or year, page number
Size	Exact size as printed
Category	Standard load, Reinforced/XL, van, light truck, etc.
Classification	PR, Load Range or XL exactly as printed, or "not shown"
Load index	Single and twin values if paired
Service configuration	Single or twin, and wheel position if given
Pressure heading	Units (bar, kPa, psi) and basis (cold)
Capacity heading	Units (kg, lb) and basis (per tire or per axle)
Entry	The cell value at the chosen pressure
Conditions	Footnotes, speed or camber limits, other notes

What a table entry does and does not tell you

A completed row tells you what the publisher's table says that tire can carry at that cold pressure under the stated conditions. It does not set the inflation pressure for your vehicle, and it does not approve a different size or load classification as a replacement. The vehicle manufacturer's recommended pressures and approved tire specifications, shown on the door-jamb placard and in the owner's manual, govern those decisions. Where a table entry and your vehicle's needs seem to conflict, a qualified tire professional should make the fitment call.