Open a Yokohama truck and bus catalog and the specification tables look dense: pattern code, size, ply rating, then something like 156/150L (154/150M), then widths, diameters, loaded radius and rim sizes. The load index and speed symbol column is the most important information in the table, because it tells you how much each tire can carry and how fast. It is also where mistakes begin. Many buyers read only the first number, or assume a bracketed second marking is a typo. This guide explains how to read Yokohama’s load and speed markings, converts them to kilograms and pounds, shows how they relate to the pressure you run, and uses the 2023-24 Asia and Oceania truck and bus radial catalog as the source for examples. For the broader picture, start with the truck tire pressure chart pillar.
The anatomy of a service description
Take the 315/80R22.5 156/150L (154/150M) that appears in several Yokohama patterns. The size, 315/80R22.5, gives section width, aspect ratio and rim diameter. The two numbers 156/150 are the load indexes for single and dual fitment. The letter L is the speed symbol, 120 km/h. The bracketed part, (154/150M), is a second service description. Yokohama states in its catalog that some tires carry a second load and speed index marking which indicates supplementary operational possibilities. It means that the tire may be used at a higher speed category (M, 130 km/h) at a lower single-fitment load index (154 instead of 156). The dual index stays at 150.
The Firestone data book that we cite elsewhere gives the full definitions. The load index is a code for the maximum load a tire can carry at the speed shown by its speed symbol. The speed symbol is the maximum speed at which the tire can carry the load of its load index. L is 120 km/h, M is 130 km/h, K is 110 km/h and J is 100 km/h. Choose the marking that matches your actual speed, never the one that looks best on paper.
Converting load index to kilograms and pounds
The load index is not the load itself. It is a code. The conversion table in the Firestone data book, which follows ETRTO, gives the load per tire for each index:
| Load index | kg per tire | lb per tire |
|---|---|---|
| 124 | 1,600 | 3,527 |
| 126 | 1,700 | 3,748 |
| 132 | 2,000 | 4,409 |
| 135 | 2,180 | 4,806 |
| 136 | 2,240 | 4,938 |
| 143 | 2,725 | 6,008 |
| 148 | 3,150 | 6,945 |
| 150 | 3,350 | 7,386 |
| 152 | 3,550 | 7,826 |
| 154 | 3,750 | 8,267 |
| 156 | 4,000 | 8,818 |
| 158 | 4,250 | 9,370 |
| 160 | 4,500 | 9,921 |
| 165 | 5,150 | 11,354 |
The absolute difference between neighboring indexes grows as you go up. From 124 to 126 the load rises by 100 kg (6 percent); from 156 to 158 it rises by 250 kg (6 percent); from 158 to 160 by 250 kg (5.9 percent). Each index point is therefore worth roughly 3 percent, and a two-point difference means about 6 percent more capacity. That is why 154/150 and 156/150 are meaningfully different on a steer axle.
Yokohama examples: what the table tells you
The following examples come from the Yokohama 2023-24 catalog and show the load and speed marking, with capacities converted using the table above. Single capacity is per tire in single fitment; dual capacity is per tire in dual fitment.
| Size | Yokohama marking | Single (kg) | Dual per tire (kg) | Notes |
|---|---|---|---|---|
| 11R22.5 | 148/145M | 3,150 | 2,900 | Regional, 16PR |
| 295/80R22.5 | 152/148M | 3,550 | 3,150 | Most common drive and steer size |
| 315/60R22.5 | 154/148L | 3,750 | 3,150 | Low-profile steer |
| 315/70R22.5 | 154/150L (152/148M) | 3,750 | 3,350 | Second marking at higher speed |
| 315/80R22.5 | 156/150L (154/150M) | 4,000 | 3,350 | 20PR in some patterns |
| 385/65R22.5 | 158L or 160J (158L) | 4,250 to 4,500 | — | Wide-base, single only |
| 425/65R22.5 | 165K | 5,150 | — | Wide-base, 20PR |
| 215/75R17.5 | 126/124M | 1,700 | 1,600 | Regional, 14PR |
| 235/75R17.5 | 132/130M | 2,000 | 1,900 | Regional, 14PR |
| 245/70R19.5 | 136/134M | 2,240 | 2,120 | 16PR |
| 265/70R19.5 | 143/141J (RY023T trailer) | 2,725 | 2,575 | Trailer use only |
Three points deserve attention. First, the trailer tire RY023T in 215/75R17.5 carries index 135/133J, against 126/124M for the standard version: 28 percent more load capacity. Yokohama notes in its catalog that the higher load index is for trailer use only. Second, the 385/65R22.5 appears in two versions: 158L in the RY253 and 106ZS patterns, and 160J (158L) in the RY357 and MY507A patterns. A 160J carries 5.9 percent more than a 158L at its rated speed. Third, the dual per-tire capacity is always lower than the single capacity: 3,150 against 3,550 kg for the 295/80R22.5, a difference of 11 percent.
From load index to inflation pressure
The load index tells you what the tire can carry at its maximum pressure. To choose your working pressure you need the load table for your size, which is published separately by distributors. The Yokohama catalog we reviewed does not print the pressure ladder, but it gives two clear instructions. First, truck tires must be inflated to a pressure suitable for the load, speed and conditions of use, to produce even wear, traction and stability. Second, Yokohama recommends maintaining proper inflation with a calibrated gauge, an inflation pressure sticker or TPMS. Use the load index as the upper limit and the real axle weight as the starting point for the lower limit, as described in our guide to the axle weight method.
- Weigh the axle, divide by the number of tires.
- Compare with the single or dual capacity for the tire’s index.
- If the tire is at more than 85 percent of its index capacity in normal service, consider a higher index or load range.
- Find the pressure in the distributor’s table that carries the load plus a margin.
- Record the pressure on the vehicle and in your log.
Yokohama’s inflation and wear guidance
The catalog’s technical pages give practical rules that match the other manufacturers:
- Check cold, at least every two weeks, with a calibrated gauge. Tires with lower profiles must be checked strictly because their sidewall deflection is less visible.
- Under-inflation causes abnormal tire deflection that builds up heat and risks failure, and causes wear on both shoulders.
- Over-inflation increases the risk of impact breaks and other road hazard damage, and causes wear in the center.
- Never inflate beyond 1.5 bar before placing the tire and wheel assembly in a safety cage.
- Use a safety cage when seating beads or inflating to operating pressure, and never stand, lean or reach over the assembly during inflation.
- Do not mix radial and bias tires on the same axle.
- Regrooving must be done when only 2 to 3 mm of the original tread pattern remains.
The catalog also lists causes of irregular wear. Under-inflation or overload is the first cause of shoulder wear and a contributing cause of other patterns, while over-inflation and improper matching of tires and rims cause center wear. These match what Goodyear and Hankook say, and appear in our guides to underinflation damage and overinflation and uneven wear.
Reading the other columns: diameter, radius and rims
The size table also lists overall width, overall diameter, loaded radius, measuring rim and approved rims. These matter for fitting and matching:
| Size | Pattern examples | Overall width (mm) | Overall diameter (mm) | Loaded radius (mm) | Measuring rim (in) | Approved rims (in) |
|---|---|---|---|---|---|---|
| 295/80R22.5 | 107ZL, 704R | 299 to 303 | 1,053 to 1,064 | 478 to 497 | 9.00 | 8.25, 9.00 |
| 315/80R22.5 | 110L, 124R, 704R | 312 to 316 | 1,072 to 1,093 | 496 to 510 | 9.00 | 9.00, 9.75 |
| 385/65R22.5 | 126S, RY357, MY507A | 376 to 380 | 1,074 to 1,082 | 483 to 501 | 11.75 | 11.75, 12.25 |
| 425/65R22.5 | RY253 | 420 to 422 | 1,126 to 1,134 | 520 | 13.00 | 12.25, 13.00, 14.00 |
| 11R22.5 | 112R, TY287, MY507 | 272 to 278 | 1,052 to 1,072 | 493 to 502 | 8.25 | 7.50, 8.25 |
Note how the overall diameter of the same size varies by 11 to 30 mm between patterns. A 315/80R22.5 in one pattern is 1,072 mm tall and in another 1,093 mm, a difference of 21 mm, or about 66 mm in circumference. If you mix patterns in a dual, the diameter difference alone can break the limits described in our post on dual tire matching. Always check the specific pattern’s diameter, not just the size.
Why this matters for cost
Load index choice is a cost decision. A higher index costs more but gives headroom that can prevent overload damage. A lower index saves money but runs closer to its limit, where heat and fatigue accumulate. The right choice depends on your real axle weights, not on the vehicle’s maximum rating. Combine the index with a pressure policy and a weekly routine, as outlined in our weekly pressure check guide, and measure the effect on total cost of ownership.
FAQ
What does the second marking in brackets mean?
It is a supplementary service description allowing a different combination of load and speed. For example, 156/150L (154/150M) allows 4,000 kg single at 120 km/h or 3,750 kg single at 130 km/h.
Is a 158L the same as a 160J?
No. 160J carries 4,500 kg up to 100 km/h; 158L carries 4,250 kg up to 120 km/h. The J version is rated for lower speeds, which is why Yokohama lists 160J (158L) on some tires.
Can I use a trailer-only tire on a drive axle?
No. Trailer-only versions such as the RY023T are intended for non-driven axles. Use the version approved for your position.
Key takeaways
The load index and speed symbol are the starting point for pressure. Learn to convert them, read second markings and check pattern-specific diameters. Then set pressure from real axle weights and check cold regularly. Continue with our pressure management hub for further guidance.
