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
Editorial Review
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.