Semi Truck Tire Sizes
Wide-Base Single Tires
A wide-base single tire — often called a super single — replaces a dual assembly with one wide tire per wheel end. The appeal is weight savings and potentially lower rolling resistance, but the tradeoff is different spare logistics, no redundancy if a tire fails on the road, and wheels that are not interchangeable with a standard dual setup.
Wide-base singles require different wheels, specific load ratings, and a different maintenance mindset. Check fleet policy, trailer compatibility, and spare availability before converting any axle.
Common wide-base single sizes
Wide-base singles use metric sizing with a wider section width than standard highway tires. Common sizes and typical applications are below. Exact dimensions and load ratings vary by brand and model — confirm from the manufacturer's data.
| Size | Typical use | Approx overall diameter | Typical wheel width required |
|---|---|---|---|
| 445/50R22.5 | Drive axle — most common wide-base drive size | 39.3 – 39.9 in | 14.0 – 15.0 in |
| 455/55R22.5 | Drive axle — slightly wider and taller option | 41.5 – 42.0 in | 14.0 – 15.0 in |
| 425/65R22.5 | Trailer axle — common trailer super single | 41.2 – 41.8 in | 12.25 – 13.0 in |
| 385/65R22.5 | Trailer axle — narrower trailer option | 39.6 – 40.2 in | 11.75 – 13.0 in |
Wide-base vs dual assembly comparison
| Area | Standard dual setup | Wide-base single |
|---|---|---|
| Tires per wheel end | 2 | 1 |
| Weight per wheel end | Higher (two tires + inner wheel hardware) | Lower (one tire on a wide-flange wheel) |
| Backup if tire fails | Dual mate may allow slow-speed movement | No backup — immediate service required |
| Wheel compatibility | Standard 8.25–9.75 in rims | Requires 12.25–15.0 in wide-flange wheels |
| Spare logistics | Standard duals widely available | Wide-base spare must be carried or sourced specifically |
| Inspection approach | Check both tires and inside sidewall | One tire but inspect full tread width and both sidewalls |
What to verify before converting an axle
- Carrier, fleet, or customer policy — some operations prohibit wide-base on certain positions or routes.
- Wheel inventory — conversion requires replacing all wheels on the converted axle.
- Load rating — the single wide-base tire must carry the full axle-half load that two dual tires previously shared.
- Trailer compatibility — not all trailer axle configurations support wide-base tire fitment.
- Spare plan — a wide-base spare must be sourced, carried, or a roadside plan established.
- State or jurisdiction rules — some jurisdictions have specific rules for wide-base tires on certain road types.
Load rating for wide-base singles
A wide-base single replaces two dual tires, so its single-position load rating must cover the full load previously split between two tires. For a tandem drive axle carrying 34,000 lb across eight dual tires (four wheel ends, two tires each), converting to four wide-base singles means each tire must carry roughly 8,500 lb — significantly more than a standard drive dual tire rating. Confirm the specific tire's rated capacity from the manufacturer's load/inflation table before any conversion.
Size Verification Checklist
- Confirm fleet and carrier policy permits wide-base tires on the intended position.
- Verify wheel width compatibility before ordering tires.
- Check load rating covers the full single-position load from the manufacturer's table.
- Establish a spare tire plan before putting the converted vehicle into service.
- Inspect full tread width and both sidewalls — there is no inside dual to hide damage.
FAQ
What is a wide-base single tire and how is it different from a standard truck tire?
A wide-base single tire (super single) is a single wide tire that replaces the dual-tire assembly used on most drive and trailer axle positions. It mounts on a single wide-flange wheel per wheel end instead of two standard-width wheels with two tires. Wide-base singles are wider, require different wheels, and have a load rating structure designed to carry the full load that two dual tires previously shared. They are not compatible with standard dual wheel setups.
Are wide-base single tires safer than dual tires?
Wide-base singles have different safety considerations than dual assemblies, not simply better or worse. Dual tires provide limited backup if one tire loses pressure — the other may allow slow-speed movement to safety. Wide-base singles provide no such redundancy; a failure requires immediate service. On the other hand, wide-base singles eliminate some dual-related problems like trapped debris and mismatched pressure. Fleet policy, spare logistics, and the specific application determine whether the trade-offs are appropriate.
Can I put a standard spare tire on a wheel end converted to wide-base singles?
No. Wide-base single tires require wider wheel flanges than standard dual tires use. A standard spare will not fit the wide-flange wheel. Converting to wide-base singles requires either carrying a matching wide-base spare, pre-positioning spares along common routes, or establishing a roadside service plan. The spare logistics are one of the most important planning items before any wide-base conversion.
Source Notes
- Manufacturer Michelin Truck Tire Data Book / Load and Inflation Resources
- Manufacturer Goodyear Commercial Truck Tire Resources
- Manufacturer Continental Commercial Vehicle Tire Care Resources
- Site note TruckTireGuide.com editorial notes