Tires are the only part of a vehicle that touches the trail, and for most off-road drivers they are the upgrade that makes the biggest difference. They are also the upgrade most often chosen for looks. An aggressive tread can be the wrong tire for how a vehicle is really used, and a larger size can quietly change load capacity, gearing, braking and handling. This guide explains tire types, the sizing systems on the sidewall, load and speed ratings, and what changes when you fit bigger tires. It draws on BFGoodrich’s 4×4 driving guide and on tire care and replacement guidance from the US Tire Manufacturers Association (USTMA). It explains categories, not individual tire models. Requirements for your vehicle come from its tire placard, owner’s manual and tire manufacturer.
All-terrain versus mud-terrain
BFGoodrich notes that unless you are building for racing or extreme rock crawling, the choice will usually be between all-terrain and mud-terrain tires, and warns against choosing on aggressive looks alone.
| All-terrain (A/T) | Mud-terrain (M/T) | |
|---|---|---|
| Tread | Less aggressive, tighter tread | Large tread blocks and wide voids that eject mud and soil |
| On road | Better comfort, quieter, better handling | Noisier and less fuel-efficient |
| Off road | Holds its own on moderate trails | Built for mud, ruts, rocks and loose soil |
| Snow | Tends to perform well on snowy roads (more siping) | Can work well in deep snow when aired down |
| Suits | Daily drivers that also use trails | Vehicles that spend more time on the trail than the road |
Those characteristics are from BFGoodrich’s guide, which adds that in mud, standard all-terrains can clog and lose grip, while self-cleaning mud-terrain treads are designed for it. Compare in more depth in all-terrain tires and mud-terrain tires.
Winter ratings
If you drive in snow, look for the Three-Peak Mountain Snowflake (3PMSF) symbol on the sidewall. BFGoodrich explains that it means the tire meets or exceeds the minimum requirements to be classified as winter-rated. Not all off-road tires carry it, so check each model you consider.
Reading the sizing systems
Off-road tires come in three sizing systems, and BFGoodrich warns not to mix them up or guess when converting between them:
- P-metric (passenger) tires are common on new SUVs and light trucks, often chosen for fuel economy. BFGoodrich describes them as not built for the demands of off-roading and a likely weak link.
- LT-metric (light truck) tires are engineered for light trucks and are stronger and more durable than passenger tires, for towing, hauling and off-road use. BFGoodrich says never to replace original LT tires with P-metric tires, because you lose load capacity and durability.
- High-flotation tires use a different, simpler sizing format and offer a bigger footprint, useful in sand, mud and snow where staying on top of the surface matters.
Load index and speed rating
Every tire carries a load index (how much weight it can carry at its specified pressure) and a speed rating. USTMA’s replacement guidance is clear on what you should not compromise:
- Replacement tires should be the same size, load index and speed rating designation as recommended by the vehicle or tire manufacturer.
- They should not be of a smaller size or lower load-carrying capacity than originally specified, which USTMA warns could be dangerous.
- Your tire specifications are usually on a label inside the driver’s door, in the glove box or in the fuel door, and in the owner’s manual.
USTMA recommends replacing all four tires together. If you replace only two, it advises installing the new pair on the rear axle for better stability. Off-road accessories, camping gear and passengers all add load, so check that your tires’ load rating still covers the vehicle as you actually use it.
Pressure: on road and off road
USTMA calls proper inflation perhaps the most important tire condition to monitor. Under-inflated tires build up heat and stress, causing irregular wear and internal damage; over-inflated tires are more easily cut or punctured on obstacles. It recommends checking pressure with a gauge at least monthly and before long trips or heavy loads, with tires cold (parked at least three hours), and notes that pressure changes by one to two psi for every 10 degrees Fahrenheit of temperature change.
Two points matter for off-road vehicles in particular:
- Changed tires, changed pressures. BFGoodrich explains that when you upgrade from P-metric to LT-metric or flotation tires, or to a larger size, the placard pressures no longer apply, because those tires have different load and inflation requirements. It advises consulting the tire manufacturer or a tire professional for the correct pressure for your setup.
- Airing down for off-road traction increases the tire’s footprint, but BFGoodrich stresses there is no universal number: the right pressure depends on tire type, terrain and vehicle weight. Carry an accurate gauge and a compressor so you can reinflate before returning to pavement.
Gauges, compressors and deflators are covered in tire pressure equipment.
Going bigger: what changes
Larger tires add clearance and footprint, but BFGoodrich is explicit about the consequences:
- Larger-than-stock tires often require modifications such as a lift kit, and may mean adjusting brake lines, steering geometry and suspension components.
- Those changes can affect handling and increase rollover risk.
- Bigger tires alter the effective gear ratio, the speedometer reading and braking performance.
- Larger tires typically require less pressure to carry the same load, so pressures must be recalculated.
Check also whether the change affects your vehicle warranty or insurance. Lift kits and suspension changes are covered in lift kits and suspension systems.
Inspecting off-road tires
Trail use is hard on tires. USTMA’s routine applies, with more frequent checks:
- Tread depth: replace at 2/32 inch, when the built-in wear bars are flush with the tread. USTMA’s penny test: if you can see all of Lincoln’s head when the penny is placed upside down in a groove, it is time for new tires.
- Damage: look for cuts, gouges, uneven wear and other signs of damage on the tread and sidewalls after each trip.
- Rotation and alignment: rotate as the owner’s manual recommends (USTMA suggests every 5,000 to 8,000 miles if no period is given), and have alignment checked after hard impacts or if the vehicle pulls. BFGoodrich notes alignment is easily knocked out after trail time.
Don’t forget the spare: check its pressure and condition, and make sure it matches the size you now run. All tire and suspension guides are under tires and suspension.
Questions to ask before buying
- What terrain do I drive most, and how much of my driving is on pavement?
- Does the tire’s load index meet or exceed my vehicle’s specification, as loaded?
- Is it LT-metric if my vehicle came with LT tires?
- Do I need the 3PMSF winter symbol?
- If I am changing size, what modifications and new pressures will it need?
