Trailer tires
What does a trailer tire's load index actually mean in pounds?
A load index is a two or three digit code molded onto a trailer tire's sidewall next to the speed rating, and it converts to an exact pound figure through a published tire industry table. A higher index is not a percentage or an estimate: index 100 means precisely 1,764 lb at that tire's maximum cold pressure, no more and no less, and index 101 means 1,819 lb. There is no rounding and no interpolation between listed indexes.
This page reproduces the full published table for the range that appears on trailer tires, from index 75 through 126. Work out the index your own axle load needs with the trailer tire load calculator, which also applies the reserve target covered below, then use the table to check any tire's sidewall against a real number.
What does each load index mean in pounds?
Read the index stamped on the tire's own sidewall against this table. This is the full published range that appears on ST trailer tires; an index outside this range does not appear on trailer applications and is not extrapolated here.
Load index 117, the rating on the Goodyear Endurance ST225/75R15, carries 2,833 lb per tire at maximum cold pressure.
Published standard A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.
| Index | Lb per tire | Index | Lb per tire | Index | Lb per tire | Index | Lb per tire |
|---|---|---|---|---|---|---|---|
| 75 | 853 lb | 76 | 882 lb | 77 | 908 lb | 78 | 937 lb |
| 79 | 963 lb | 80 | 992 lb | 81 | 1,019 lb | 82 | 1,047 lb |
| 83 | 1,074 lb | 84 | 1,102 lb | 85 | 1,135 lb | 86 | 1,168 lb |
| 87 | 1,201 lb | 88 | 1,235 lb | 89 | 1,279 lb | 90 | 1,323 lb |
| 91 | 1,356 lb | 92 | 1,389 lb | 93 | 1,433 lb | 94 | 1,477 lb |
| 95 | 1,521 lb | 96 | 1,565 lb | 97 | 1,609 lb | 98 | 1,653 lb |
| 99 | 1,709 lb | 100 | 1,764 lb | 101 | 1,819 lb | 102 | 1,874 lb |
| 103 | 1,929 lb | 104 | 1,984 lb | 105 | 2,039 lb | 106 | 2,094 lb |
| 107 | 2,149 lb | 108 | 2,205 lb | 109 | 2,271 lb | 110 | 2,337 lb |
| 111 | 2,403 lb | 112 | 2,469 lb | 113 | 2,535 lb | 114 | 2,601 lb |
| 115 | 2,679 lb | 116 | 2,756 lb | 117 | 2,833 lb | 118 | 2,910 lb |
| 119 | 2,998 lb | 120 | 3,086 lb | 121 | 3,197 lb | 122 | 3,307 lb |
| 123 | 3,417 lb | 124 | 3,527 lb | 125 | 3,638 lb | 126 | 3,748 lb |
This is the full published load index range used on trailer tires. An index outside 75 to 126 does not appear on ST trailer applications in this catalog and is not extrapolated.
How much reserve should you build in above the minimum index?
The conventional target is roughly 15 percent of reserve above the calculated load per tire, because a tandem axle in a turn or on a crowned road puts more than its share on one corner.
Rule of thumb Widely taught towing convention rather than a published specification. It is a good starting point and it is not a rating.
| Calculated load per tire | Minimum index (no reserve) | With 15% reserve | Recommended index (with reserve) |
|---|---|---|---|
| 1,000 lb | Index 81 (1,019 lb) | 1,150 lb | Index 86 (1,168 lb) |
| 1,500 lb | Index 95 (1,521 lb) | 1,725 lb | Index 100 (1,764 lb) |
| 2,000 lb | Index 105 (2,039 lb) | 2,300 lb | Index 110 (2,337 lb) |
| 2,500 lb | Index 113 (2,535 lb) | 2,875 lb | Index 118 (2,910 lb) |
The 15 percent reserve is a widely taught towing convention, not a published requirement. The index-to-pound conversion itself is the published figure; only the decision to build in headroom above the calculated minimum is convention.
Which catalog tires carry which load index?
The Goodyear Endurance ST225/75R15 carries index 117, or 2,833 lb per tire, and the Carlisle Radial Trail HD in the same size carries index 113, or 2,535 lb.
Published standard A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.
| Tire | Load index | Lb per tire |
|---|---|---|
| Goodyear Endurance ST225/75R15 | 117 | 2,833 lb |
| Goodyear Endurance ST205/75R15 | 107 | 2,149 lb |
| Goodyear Endurance ST205/75R14 | 105 | 2,039 lb |
| Goodyear Endurance ST215/75R14 | 108 | 2,205 lb |
| Carlisle Radial Trail HD ST225/75R15 | 113 | 2,535 lb |
| Carlisle Radial Trail HD ST205/75R15 | 107 | 2,149 lb |
Load index values here are read from each tire's own manufacturer listing, not estimated from tire size.
Frequently asked questions
What does load index 117 mean in pounds?
Load index 117 means 2,833 lb per tire at that tire's maximum cold inflation pressure. It is a published, fixed conversion rather than an estimate, and it is the rating stamped on several ST225/75R15 trailer tires in our catalog, including the Goodyear Endurance. The pound figure only applies at the tire's own maximum psi, not at a lower running pressure.
How do I convert a load index to pounds myself?
Read the two or three digit index molded next to the speed rating on the tire's sidewall, then look it up against the published load index table, which runs from 75 to 126 for trailer-relevant sizes. Each index has one fixed pound value; there is no rounding or interpolation between listed numbers.
Why build in a 15 percent reserve above the calculated minimum index?
A trailer loads unevenly side to side, and a tandem axle in a turn or on a crowned road routinely puts more than its calculated share onto one corner tire. Sizing to the bare minimum index leaves no margin for that, so towing convention targets roughly 15 percent above the calculated per-tire load before picking an index.
Can I use a higher load index than my trailer needs?
Yes, and it is generally the safer direction to round toward when a calculated load falls between two published index values. A higher index simply means more reserve capacity at the same maximum pressure; it does not require running a different pressure or change anything else about how the tire is used.
Does load index change with tire size?
Load index is independent of tire size in the sense that two different sizes can share the same index and the same pound rating, but a given tire model is only sold at specific index values for each size it comes in. Always read the index stamped on the specific tire, not assumed from a similar-looking size.
What happens if I run a tire below its published load index requirement?
The tire is asked to carry more weight than its sidewall rating supports, which raises heat and sidewall flex at highway speed and is a documented cause of tread separation. Recalculate the load per tire and step up to a tire with a load index that meets or exceeds it, ideally with the conventional reserve built in.
Free download
Get the complete tow rig setups emailed to you
Both ladders, conventional travel trailer and fifth wheel, at beginner, intermediate and expert budgets, every item priced and linked with a running total, plus a printable pre-trip weighing worksheet you can fill in at the scale.
One email with the setups. No sequence, no sharing your address, unsubscribe any time.
Researched, not professional advice. This page is compiled from published standards, manufacturer towing guides and product specifications, and owner-review consensus, not hands-on testing. Figures described as a rule of thumb are towing convention rather than published standards, and they are labelled that way wherever they appear. Nothing here overrides your own ratings. Work your payload sum before your tow rating, because payload is the limit that actually binds on most half ton trucks and nearly every SUV. Load a conventional trailer to 10 to 15 percent tongue weight and a fifth wheel to 15 to 25 percent pin weight, and never lighter: a tail heavy trailer is what starts sway. Weigh the rig loaded rather than trusting a brochure dry weight. A weight distribution hitch and a set of air bags both restore ride height and control, and neither one raises a single rating. Trailer brakes are required by state law above a threshold that varies by state, and a breakaway battery that has quietly gone flat is the normal condition of most trailers on the road.