Trailer tires
How fast can you actually tow, and is that a tire question or a law question?
Two entirely different limits govern how fast you can tow, and they get confused constantly because both show up as a single number in a driver's head. One is a tire speed rating, a physical limit on how fast a specific tire can safely operate published by its manufacturer. The other is a legal speed limit, a rule a state posts for vehicles towing a trailer, which is a matter of law rather than physics and can be lower than the general highway limit.
A tire can be legally driven below its rated speed all day. A tire cannot be safely driven above its rated speed no matter what the posted limit says, because exceeding a tire's speed rating causes heat buildup inside the tire structure that a standard highway speed does not, and sustained heat is a documented cause of tread separation.
On this page
- What speed are most ST trailer tires actually built for?
- Why does exceeding a tire's speed rating matter more on a trailer tire than a car tire?
- Do states post a lower speed limit for towing?
- What happens when the legal limit and the tire rating disagree?
- How do you find your own tire's actual speed rating and your own state's towing limit?
What speed are most ST trailer tires actually built for?
The industry default speed rating for a Special Trailer tire is 65 mph unless the sidewall states a higher figure, and some newer tires are built and marked for 75 or 81 mph.
Published standard A published, traceable figure: a standards body, a federal regulation or a manufacturer specification states it.
| Speed rating | What it means |
|---|---|
| 65 mph | The default industry speed rating for a standard ST trailer tire when the sidewall states no higher figure |
| 75 mph | A rating some newer ST tire constructions carry, stated explicitly on the sidewall or in the manufacturer's published specification |
| 81 mph | A rating a small number of premium ST tires carry, again stated explicitly rather than assumed |
This is a published, traceable industry figure, not a rule of thumb: the tire and its sidewall marking are the authority for a specific tire. The Carlisle Radial Trail HD ST225/75R15 is one example whose own manufacturer listing states an 81 mph speed rating, above the 65 mph industry default. Never assume a higher rating without reading it directly off your own tire's sidewall or the manufacturer's specification for that exact model.
Why does exceeding a tire's speed rating matter more on a trailer tire than a car tire?
An ST tire is engineered for a trailer's static, straight-line load rather than for the cornering forces a passenger car tire is built to handle, and it runs at a higher percentage of its structural limit under a given load than a comparable car tire does. Sustained speed above the rated figure increases the flexing and internal heat generation in the sidewall and belt package beyond what the tire was engineered to dissipate continuously. That heat is the direct mechanism behind tread separation, which on a trailer tire frequently happens with no warning beyond a sudden noise and a hard pull to one side.
Under-inflation compounds the exact same failure mode: a soft tire flexes more per rotation, generating more heat at any given speed, which is why running the maximum sidewall cold pressure is not optional on a trailer tire the way running the door placard pressure is on a car. See how to check trailer tire pressure for the full procedure.
Do states post a lower speed limit for towing?
Some do, and the threshold and the exact rule genuinely vary by state, in the same way that the trailer brake requirement threshold varies by state and is not published on this site as a single national figure. A handful of states post a specific maximum speed for any vehicle towing a trailer that is lower than the general highway speed limit, others apply the general limit to towing without exception, and the details of which vehicles and trailers are covered differ further still.
This site does not publish a per-state towing speed limit table, for the same reason it does not publish a per-state trailer brake law table: fifty rows across fifty separate and periodically changing state statutes is not something that can be sourced and kept accurate reliably from one page, and a wrong row read as fact is worse than admitting the limit varies. Check the specific state you are driving in, and the state you are driving through if it differs, using that state's own department of transportation or DMV publication before a long trip.
What happens when the legal limit and the tire rating disagree?
Whichever of the posted legal limit and the tire's own speed rating is lower is the speed you should actually drive at, regardless of which one is more convenient.
Rule of thumb Widely taught towing convention rather than a published specification. It is a good starting point and it is not a rating.
| Situation | What governs |
|---|---|
| Posted limit is 70 mph, tires are rated to 65 mph | 65 mph. The tire cannot safely exceed its own rating no matter what the road sign says. |
| Posted towing limit is 55 mph, tires are rated to 81 mph | 55 mph. The tire's higher rating does not override a lower posted legal limit. |
| Sidewall speed rating is unmarked | Treat it as the 65 mph industry default and confirm with the tire manufacturer if in doubt. |
This is straightforward logic rather than a published rule of its own: you are always bound by the lower of a legal limit and a physical equipment limit, the same principle that applies to a tow rating and a payload rating disagreeing on the same trip.
How do you find your own tire's actual speed rating and your own state's towing limit?
- Read the tire sidewall. The speed rating, when the tire carries one above the 65 mph default, is stated directly on the sidewall along with the tire size and load range.
- Check the tire manufacturer's published specification. If the sidewall marking is unclear or worn, the manufacturer's own listing or spec sheet for that exact model states the rating.
- Look up the towing speed rule for the state you are in. Search that state's department of transportation or DMV site directly for its towing speed provision rather than relying on a secondhand summary.
- Repeat for any state you are driving through. A road trip crossing state lines can cross more than one towing speed rule, and the lower one applies while you are in that state.
- Drive to whichever figure is lower. The tire's rating and the legal limit are independent ceilings, and the lower one is your actual safe and legal speed.
Frequently asked questions
What is the speed rating on a standard ST trailer tire?
The industry default for a Special Trailer tire is 65 mph, and this applies unless the sidewall states a higher figure. Some newer ST tire constructions are built and explicitly marked for 75 or 81 mph, but that higher rating has to be stated on the specific tire rather than assumed, since it is not the default across the category.
Is there one federal speed limit for towing a trailer?
No. Towing speed limits are set at the state level and genuinely vary, the same way the trailer brake law threshold varies by state. Some states post a lower maximum speed specifically for vehicles towing a trailer, others apply the general highway limit without a separate towing provision. Check the specific state you are driving in rather than assuming one figure applies everywhere.
What happens if I drive faster than my tire's speed rating?
Sustained speed above a tire's rated limit increases internal heat generation in the sidewall and belt package beyond what the tire is engineered to dissipate continuously, and that heat buildup is a documented cause of tread separation. This can happen with little or no warning at highway speed, which is why the tire's own rating, not the posted road limit, is the ceiling that actually governs how fast is safe.
If the speed limit is higher than my tire's rating, which one do I follow?
The lower of the two always governs your actual safe driving speed. A posted legal limit of 70 mph does not make a tire rated to 65 mph safe at 70 mph, because the tire's rating is a physical engineering limit rather than a suggestion. Drive to whichever figure, the legal limit or the tire rating, is lower on that stretch of road.
Why doesn't this site publish a state by state towing speed limit table?
Because fifty state statutes, each capable of changing independently, cannot be sourced and kept reliably accurate from a single reference page, and a wrong row in a safety-relevant table is worse than none at all. This is the same reasoning behind not publishing a per-state trailer brake law table elsewhere on this site. Check the specific state's own department of transportation or DMV source directly.
Does under-inflation make the speed rating issue worse?
Yes, through the same mechanism. An under-inflated tire flexes more with every rotation, which generates more internal heat at any given speed, so a soft tire can overheat and fail well below its rated speed even while nominally under the limit. Running the tire's maximum cold sidewall pressure, not a lower comfort pressure, is part of what makes the published speed rating apply in the first place.
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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.