Truck Tire Load Ratings
Axle Weight vs Tire Capacity
A tire capacity check starts with the axle, not the tire catalog. If the loaded axle weight is unknown, the comparison is only a guess.
The example below is intentionally simple and marked example only; real decisions require verified axle weights and official tire data.
Example only — steer axle
| Input | Example value | Meaning |
|---|---|---|
| Loaded axle weight | 12,000 lb | From a scale ticket or documented fleet record |
| Tires on axle | 2 | Single steer axle, one tire per side |
| Load per tire (rough) | 6,000 lb | Axle weight divided by tire count — not accounting for side-to-side imbalance |
| Rated capacity per tire | Confirm from manufacturer table | Do not use a number from another source |
Federal axle weight limits as a reference
Federal highway regulations (23 U.S.C. 127) limit single axles to 20,000 lb and tandem axles to 34,000 lb on Interstate highways. These are road-use limits, not tire capacity limits — both must be respected independently. A tire capacity check compares against the actual loaded weight, not against the legal maximum.
Why axle math is only a screen
Dividing axle weight by tire count assumes the load is perfectly balanced side to side. Real trucks rarely load that neatly. Fuel level, fifth-wheel position, cargo placement, trailer loading, road crown, and suspension condition can all change how much each tire is carrying.
If the rough calculation shows only a small margin, treat that as a reason to gather better data, not as a pass. The closer the numbers are, the less room there is for side-to-side imbalance, gauge error, pressure loss, or a wrong table entry.
When to re-weigh
Recheck axle weights after a major cargo change, fifth-wheel adjustment, trailer swap, or equipment modification. A pressure or capacity decision made from last month's load may be wrong for today's axle split, even if gross weight looks similar.
Use the right tire count
The tire count in the quick math must match the actual position. A steer axle usually has two tires, while a tandem drive group commonly has eight tires in dual service. Wide-base singles, lift axles, tag axles, and mixed trailer setups change the count and can make a simple average misleading.
Also confirm whether the manufacturer lists the tire capacity for single or dual use. A tire in a dual assembly normally uses the dual rating, not the single rating, because heat and load sharing conditions are different.
Where errors happen
- Using empty or unloaded weight instead of the loaded axle weight
- Ignoring uneven side-to-side loading from cargo placement
- Using the single-position rating for a tire in dual service
- Forgetting that GAWR and wheel ratings still apply independently of tire capacity
- Assuming a legal road-weight limit is the same thing as tire approval
Capacity Verification Checklist
- Get the loaded axle weight when practical.
- Divide by tire count only as a rough screen.
- Use dual rating for dual positions.
- Verify official single or dual capacity from manufacturer data.
- Leave a conservative margin and inspect tire condition.
FAQ
How do I calculate how much load each tire is carrying?
Divide the loaded axle weight by the number of tires on that axle as a rough starting point. For a steer axle with two tires at 12,000 lb, each tire carries approximately 6,000 lb in a balanced scenario. For a tandem drive axle set with eight tires at 34,000 lb combined, each tire carries roughly 4,250 lb in dual service. Side-to-side loading is rarely exactly equal, so treat the division as a conservative screen, not a precise answer.
What should I do if the calculated load per tire exceeds the tire's rated capacity?
Stop and address the situation before continuing to operate. Do not proceed hoping the tire will hold. Either redistribute the cargo, reduce the load, or verify that the correct tire for that axle and load is installed. Overloading a tire generates heat that can cause internal damage or sudden failure without visible warning from outside the tire.
Does GAWR or tire capacity control how much weight can be on an axle?
Both limits apply independently, and the lower one controls. You cannot exceed GAWR because the tires have higher capacity, and you cannot exceed the tires' rated capacity because the axle hardware is rated higher. Both the vehicle certification label (for GAWR) and the tire manufacturer's data (for tire capacity) must be checked separately and both must be within their limits.
Source Notes
- Government 49 CFR 393.75 - Tires
- Manufacturer Michelin Truck Tire Data Book / Load and Inflation Resources
- Site note TruckTireGuide.com editorial notes
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TruckTireGuide.com editorial team
Maintained by an independent editor with fleet tire-program experience in regional Class 8 operations, supported by transportation regulatory research and commercial vehicle technical writing.
Pages are checked against public regulations, manufacturer resources, industry references, and conservative field practice. The site does not approve tires for service or replace qualified inspection.