The correct tire pressure when towing depends on which tires you are checking, how the rig is loaded, and what the vehicle and trailer manufacturers specify. The tow vehicle, trailer, tires, wheels, and valve stems can have different limits, so one universal PSI number is not safe for every setup.
Quick Answer
Use the cold PSI on the tow vehicle’s door-jamb label or towing instructions. For the trailer, use its tire-information placard or owner’s manual first. Some ST-tire manufacturers specify the maximum cold PSI molded on the tire, while approved LT tires may use a manufacturer load/inflation table.
Key Takeaways
- Use the vehicle placard or owner’s manual for the tow vehicle. Do not automatically inflate its tires to the maximum pressure molded on the sidewall.
- Use the trailer’s placard or manual before relying on a generic ST-tire rule.
- Check every pressure cold, ideally after the rig has been parked for at least three hours.
- Weigh the loaded rig to verify axle, payload, hitch, and tire capacity.
- Extra PSI or higher-load tires do not increase the vehicle’s GVWR, GAWR, GCWR, payload, or hitch rating.
At a Glance
| Time Required | 15–30 minutes for inspection and inflation, plus extra time if you weigh the rig |
| Difficulty | Easy to moderate |
| Tools Needed | Accurate pressure gauge, suitable air compressor, vehicle and trailer labels or manuals, flashlight, and optional trailer TPMS |
| Cost | Usually free if you own the tools; a public scale or professional inspection may charge a fee |
How Much Tire Pressure Should You Run When Towing?
The safe starting pressure comes from different places for the tow vehicle and trailer:
- Tow vehicle: Use the cold front and rear pressures on the Tire and Loading Information label, usually found on the driver-side door jamb. Follow a separate loaded or towing pressure only when the owner’s manual or manufacturer provides one.
- Trailer with its original tire size: Use the recommended cold pressure on the trailer’s tire-information or certification placard and check the trailer manual.
- Trailer with ST tires: Follow the trailer placard and the tire manufacturer’s instructions. Some ST-tire manufacturers recommend the maximum cold pressure molded on the sidewall, but that rule is not universal.
- Trailer with approved LT tires: Follow the trailer or tire manufacturer’s load/inflation information. Use the pressure required for the actual load without exceeding the tire, wheel, or valve rating.
- Replacement tires that differ from the original specification: Ask the trailer manufacturer or a qualified tire professional to confirm the approved size, load capacity, rim compatibility, and pressure.
Warning: Never inflate all tow-vehicle tires to the maximum PSI molded on the sidewall just because a trailer is attached. The sidewall figure is a tire limit associated with its rated load, not the normal pressure selected for your specific vehicle.
Where to Find the Correct Cold PSI
Check the following sources in order rather than guessing from tire appearance:
- Tow-vehicle Tire and Loading Information label: Look on the driver-side B-pillar, door edge, or door jamb.
- Tow-vehicle owner’s manual: Read the towing, loading, tires, and weight-distributing-hitch sections for any special loaded-pressure instructions.
- Trailer tire-information or certification placard: It is commonly placed near the front left side of the trailer or close to the certification label.
- Trailer owner’s manual: Check for tire size, cold pressure, cargo limits, wheel torque, speed limits, and replacement requirements.
- Tire manufacturer data: Use this when the installed tire differs from the original tire or when an approved load/inflation table is required.
The National Highway Traffic Safety Administration recommends using the vehicle manufacturer’s cold inflation pressure rather than the maximum number molded on a passenger vehicle tire.
Federal tire-selection rules also require applicable trailers to display recommended cold inflation information. The current requirements appear in 49 CFR 571.110.
Note: A replacement tire’s sidewall may show a higher maximum pressure than the trailer placard. That does not automatically mean the trailer should use the higher figure. The wheel, valve, trailer design, and actual load must all support the selected pressure.
Tow-Vehicle vs. Trailer Pressure Rules
| Tire location | Primary pressure source | Important caution |
| Tow vehicle | Door-jamb label and owner’s manual | Do not use sidewall maximum pressure as the default vehicle setting. |
| Trailer with original tires | Trailer placard and manual | Confirm that the installed size and load range match the label. |
| Trailer with replacement ST tires | Trailer and tire manufacturer guidance | Some brands specify sidewall maximum cold PSI, while others publish load tables. |
| Trailer with approved LT tires | Approved load/inflation table and trailer guidance | Capacity changes with pressure; do not exceed wheel or valve limits. |
P, LT, and ST Tires Explained
- P or passenger-car tires: Designed mainly for passenger vehicles. When a passenger-car tire is used on a multipurpose vehicle, truck, bus, or trailer, federal calculations reduce its marked load rating by dividing it by 1.10.
- LT or light-truck tires: Designed for light trucks and multipurpose vehicles. Many sizes have pressure-dependent load capacities listed in manufacturer load/inflation tables.
- ST or Special Trailer tires: Designed for trailer service. Their construction and load ratings are intended for trailer use, but the correct pressure still depends on the trailer and tire manufacturer’s instructions.
Do not install a different tire type, size, load range, or construction merely because its sidewall shows a higher capacity. It must be approved for the trailer’s rims, load, speed, clearances, and service conditions.
The tire’s load index identifies a standardized load capacity. Load range describes a tire’s strength and pressure capability category. Neither term changes the trailer’s axle or vehicle ratings.
How Load Index, Load Range, and Heat Affect Towing
A tire must carry the load placed on it at the pressure specified for that application. When pressure is too low for the load, the sidewall flexes more and produces extra heat. Overloading, excessive speed, tire damage, dragging brakes, and failing wheel bearings can also produce dangerous heat.
- Check tire capacity: The tires on an axle must have enough combined capacity for that axle’s rated and actual load.
- Check wheel capacity: A tire rated for 80, 95, or 110 PSI does not prove that the wheel can handle the same pressure or load.
- Check valve capacity: High-pressure tires require valve stems and hardware suitable for the selected cold pressure.
- Check the speed rating: Stay within the tire and trailer manufacturer’s speed limits.
- Use matching axle pressures: Tires of the same specification on the same axle should normally use the same cold pressure. In dual-wheel positions, pressure differences can cause uneven load sharing.
Professional technicians can find additional service guidance through the Tire Industry Association.
Tire pressure supports a tire’s rated load, but it cannot raise the vehicle’s certified weight ratings or repair an overloaded towing setup.
Ratings to Check Before You Tow
Safe towing depends on more than tire pressure. Confirm all of these limits:
- GVWR: Maximum permitted weight of the loaded tow vehicle or trailer.
- GAWR: Maximum permitted weight carried by a specific axle.
- GCWR: Maximum combined weight of the tow vehicle and trailer, where specified by the vehicle manufacturer.
- Payload: Occupants, cargo, accessories, hitch equipment, and trailer tongue weight carried by the tow vehicle.
- Towing capacity: Maximum trailer weight allowed by the vehicle manufacturer for the specific configuration.
- Hitch and ball rating: Maximum trailer and tongue load allowed by the hitch components.
- Tire, wheel, and valve ratings: Maximum load and pressure each component can safely support.
Warning: Increasing tire pressure, installing a higher load range, or adding a weight-distributing hitch does not increase the tow vehicle’s GVWR, GAWR, GCWR, payload, or manufacturer-rated towing capacity. The lowest applicable rating remains the limit.
How Tongue Weight Changes Tow-Vehicle Axle Load
Tongue weight is the downward force the trailer applies to the hitch. For many conventional bumper-pull trailers, a common starting range is about 10–15% of the trailer’s loaded weight. The correct range for your trailer may differ, so follow the trailer and tow-vehicle manufacturers.
Tongue weight counts against the tow vehicle’s payload. It usually adds load to the rear axle and may remove some load from the front axle. Passengers, cargo, aftermarket accessories, the hitch receiver, ball mount, and weight-distributing equipment also use payload capacity.
A properly adjusted weight-distributing hitch can transfer some load from the tow vehicle’s rear axle toward its front axle and the trailer axles. It does not remove weight or increase any rating. Follow the hitch and vehicle setup instructions, including any required front-axle restoration measurement.
Calculate Tire Loads by Weighing the Loaded Rig
The safest way to confirm that the tires and axles are not overloaded is to weigh the rig exactly as it will travel. Include people, fuel, water, propane, tools, food, batteries, cargo, and hitch equipment.
Public Scale Weighing Steps
- Load the rig for travel: Pack the tow vehicle and trailer normally, fill or empty tanks to the condition you expect to tow, and secure all cargo.
- Record the labels: Photograph the tow vehicle’s GVWR, front GAWR, rear GAWR, payload label, and tire pressure. Photograph the trailer’s GVWR, GAWR, tire size, and recommended cold pressure.
- Weigh the connected rig: Place the tow vehicle’s front axle, rear axle, and trailer axle group on separate scale platforms where possible.
- Weigh the tow vehicle without the trailer: Keep passengers and cargo in the same positions. The difference helps estimate how the hitch changes the axle loads.
- Check each rating: Compare scale readings with the tow vehicle GVWR and GAWR, trailer GVWR and GAWR, payload, GCWR, hitch rating, and tire capacities.
- Get individual wheel-position weights when available: This reveals side-to-side imbalance that a normal axle-scale reading can hide.
- Correct the load before adjusting pressure: Move or remove cargo if any rating is exceeded. Do not try to solve an overloaded axle with extra PSI.
If individual wheel-position weights are available, use the heavier wheel position when selecting an approved load-table pressure, then use the same cold pressure for matching tires across that axle. If you have only an axle total, do not assume the load is divided perfectly evenly from side to side.
Pro Tip: Take photos of every label and save them on your phone. This prevents confusion at an air station or scale and gives a tire professional the exact size, load range, axle rating, and recommended pressure.
Check and Adjust Tire Pressure Before Towing
- Park long enough for a cold reading: Check pressure before driving or after the rig has been parked for at least three hours. Avoid measuring tires after direct sun has heated one side of the rig.
- Identify each installed tire: Confirm whether it is P, LT, or ST and record its size, load range, load index, speed rating, and maximum cold pressure.
- Check the labels and manuals: Find the approved cold pressure for the tow vehicle and trailer.
- Use a suitable gauge: The gauge must cover the pressure range of the highest-pressure tire. A gauge intended for 35 PSI passenger tires may not be suitable for a 110 PSI trailer tire.
- Check every tire: Include the tow vehicle, trailer, full-size spare, temporary spare, and inside dual tires where applicable.
- Inflate to the approved cold setting: Use the vehicle placard for the tow vehicle and the trailer placard/manual or approved tire guidance for the trailer.
- Inspect tires and valves: Look for cuts, cracks, bulges, exposed cords, embedded objects, loose valve hardware, missing valve caps, uneven wear, or signs of rubbing.
- Inspect wheels and nearby components: Check for bent or cracked wheels, loose or damaged lug hardware, bearing problems, dragging brakes, and inadequate tire clearance.
- Recheck after adding air: Verify each pressure with the gauge rather than relying only on the compressor’s display.
- Perform a final walk-around: Check the coupler, safety chains, breakaway cable, lights, cargo securement, and trailer brakes before leaving.
Check Pressure and Heat During the Tow
Pressure normally rises as a tire warms. Do not bleed air from a normally warmed tire merely to return it to the cold number. Doing so can leave the tire underinflated after it cools.
- Stop early in the trip: At the first safe rest or fuel stop, walk around the rig and look for a soft tire, new bulge, rubbing, smoke, odor, or vibration.
- Compare axle mates: A tire that is losing pressure or running much hotter than the matching tire on the same axle needs investigation.
- Check for non-tire heat sources: A dragging brake or failing wheel bearing can heat the wheel and tire.
- Use TPMS as an aid: A trailer tire-pressure monitoring system can warn of pressure loss, but it does not replace cold manual checks or visual inspections.
- Recheck on long travel days: Inspect the rig at fuel and rest stops and correct the pressure when a reliable cold reading becomes available.
If a tire is clearly low while hot, add enough air to avoid driving significantly underinflated, then diagnose the cause and reset it accurately when cold. Do not continue towing on a tire with a rapid leak, visible structural damage, or exposed cords.
How Temperature Changes Tire Pressure
A common rule of thumb is that tire pressure changes by roughly 1–2 PSI for each 10°F change in ambient temperature. The exact change varies with tire size, starting pressure, load, sunlight, and operating heat.
- A tire set correctly on a warm afternoon may read lower on a cold morning.
- Direct sunlight can make tires on one side of a parked trailer read higher than shaded tires.
- Normal driving raises pressure because the tire and contained air become warmer.
- The approved cold target does not change simply because the hot reading is higher.
Recheck cold pressures after a major weather change, before long trips, and at least monthly during regular use.
Warning Signs and Common Towing Tire Problems
- Repeated pressure loss: Check for a puncture, damaged valve, loose valve core, rim leak, bead leak, or wheel damage.
- One tire running hotter: Investigate low pressure, excess load, internal damage, brake drag, bearing trouble, or a dual-tire pressure mismatch.
- Bulges or exposed cords: Remove the tire from service before towing again.
- Deep weather cracking: Have the tire inspected and replace it when the tire manufacturer or qualified professional recommends it.
- Center tread wear: May indicate excess pressure for the application, although tire construction and alignment can also affect wear.
- Shoulder wear: May indicate underinflation, overloading, cornering stress, or alignment and suspension problems.
- Cupping or irregular wear: Check balance, wheel runout, alignment, shocks, suspension, bearings, and pressure history.
- Frequent overload at the current rating: Reduce the load or use a properly rated tow vehicle or trailer. A tire upgrade alone cannot correct an exceeded axle or vehicle rating.
For additional tire inspection and safety information, see NHTSA’s tire safety resources.
When to Upgrade Trailer Tires
Consider replacing or changing the trailer tires when they are damaged, unsuitable for the load, incorrectly sized, beyond the tire manufacturer’s service recommendation, or not approved for the trailer’s normal speed and operating conditions.
Before changing size, load range, or tire type, verify:
- The new tire is approved for trailer service.
- Its load capacity is sufficient at the intended pressure.
- The wheel width and diameter are compatible.
- The wheel and valve can handle the required pressure.
- The tire clears the body, suspension, neighboring tire, and fender through the full range of movement.
- The trailer manufacturer approves the replacement specification.
A higher-load tire can provide additional tire capacity when correctly selected, but it does not increase the trailer’s GVWR or GAWR.
Frequently Asked Questions
What tire pressure should I run when towing?
Use the tow vehicle’s door-jamb pressure or its owner’s manual. For the trailer, use the tire-information placard and trailer manual. When approved replacement tires are fitted, follow the trailer and tire manufacturers’ instructions without exceeding the tire, wheel, or valve limits.
Should I use the PSI on the tire sidewall or the door sticker?
For a tow vehicle, use the door sticker or owner’s manual. The sidewall number is not the vehicle’s normal recommended pressure. For a trailer, check its placard and manual first. Some ST-tire manufacturers direct owners to use the tire’s maximum cold sidewall pressure.
Should I increase my truck’s rear tire pressure for towing?
Increase it only when the vehicle manufacturer provides a higher loaded or towing pressure for your configuration. Do not raise the rear pressure by guesswork or automatically use the tire’s sidewall maximum.
Do all ST trailer tires need maximum sidewall PSI?
No single rule covers every tire and trailer. Some ST manufacturers recommend maximum cold sidewall pressure for their products. However, you should first check the trailer placard, manual, installed tire specification, wheel rating, and tire manufacturer instructions.
How do I know if my tires are rated for the load?
Compare the installed tire specification and capacity with the vehicle or trailer GAWR and actual scale weight. If an approved load/inflation table applies, use the load on the heavier wheel position and set matching tires on that axle to the same cold pressure.
When should I check tire pressure before a trip?
Check it before driving or after the rig has been parked for at least three hours. Check all tow-vehicle tires, trailer tires, and spares. Recheck after major temperature changes and before each towing day.
Should I release air when the tires are hot?
Do not bleed normal pressure gained from driving. The pressure should rise as the tire warms. Adjust it accurately when cold unless the tire is dangerously overinflated because of an incorrect cold setting or another problem.
How much does tire pressure change with temperature?
A common estimate is about 1–2 PSI for every 10°F change in ambient temperature. Because sunlight and driving also warm tires, compare readings under similar cold and shaded conditions.
What tongue weight should I aim for?
Many conventional trailers use roughly 10–15% of loaded trailer weight, but the correct range is trailer-specific. Measure the loaded tongue weight and stay within the trailer, tow vehicle, hitch, payload, and axle limits.
Can higher tire pressure increase towing capacity?
No. Proper pressure allows the tire to carry its approved load, but it cannot increase the vehicle’s GVWR, GAWR, GCWR, payload, towing capacity, hitch rating, or wheel rating.
Conclusion
Safe towing starts with using the correct pressure source. Follow the tow vehicle’s door-jamb label or manual, then use the trailer’s tire-information placard and owner’s manual for its tires. Treat sidewall maximum pressure as a limit or product-specific instruction, not a universal setting for every part of the rig.
Check pressures cold, weigh the fully loaded setup, and confirm the vehicle, axle, payload, hitch, tire, wheel, and valve ratings. During the trip, watch for pressure loss, unusual heat, vibration, odor, or visible damage. Never try to correct an overloaded setup simply by adding more air.
Sources
- NHTSA TireWise — cold-pressure checks, vehicle placard guidance, tire inspection, and underinflation safety.
- Electronic Code of Federal Regulations, 49 CFR 571.110 — trailer tire-information labels, tire load limits, and passenger-tire derating.
- Ford Towing Guidance — tongue weight, payload, towing ratings, and public-scale weighing.
- Carlstar Tire FAQ — manufacturer-specific guidance for trailer tire inflation.
- U.S. Tire Manufacturers Association Tire Safety Fact Sheet — temperature-related pressure changes and tire-maintenance guidance.
- Toyo Tires Safety Information — cold readings and why normal hot pressure should not be bled away.
