Overland Tires: How to Choose, Inflate and How Many to Carry

Tires are the preparation item that raises the most questions and causes the most mistakes. Most Brazilian overlanders underestimate them because the car runs fine in the city on the stock tire, and then they find out on their first gravel road in Argentina or Bolivia that the problem was not the tire, it was the wrong type of tire for the wrong type of terrain. On ripio, the wrong tire is not just discomfort: it means a guaranteed flat, premature wear, and on some stretches a real risk of an accident.

This article is the practical guide to tires for an overland trip. It covers what each type delivers, how to set pressure for different terrain, how many spares to carry, and what to do when you get a flat far from any tire shop.

In short: for an overland trip through South America, the all-terrain (AT) is the tire that best balances pavement, ripio and light off-road. The stock highway tire (HT) can't handle serious ripio. The mud-terrain (MT) is overkill for most routes. Carry two spares for any trip with gravel stretches. Pressure varies: 32 to 36 psi on pavement, 26 to 28 psi on ripio, 18 to 22 psi on heavy off-road.

The three tire types and what each can handle

Highway Terrain (HT)

The tire that comes stock on most SUVs and pickups sold in Brazil. Excellent performance on pavement, quiet, comfortable, fuel efficient. On light ripio it holds up, but the compound is softer and the tread less aggressive. On severe ripio, the risk of a flat goes up and wear accelerates a lot. On trails or mud, it is not the tire.

If the trip is 90% pavement with one or two days of easy gravel, the stock HT will do. For anything more serious, swap before you leave.

All-Terrain (AT)

The tire of most overlanders. A tougher compound and an intermediate tread, it works well on pavement (more noise than an HT, slightly higher fuel consumption) and does very well on ripio, gravel, packed dirt and moderate off-road. In deep mud it starts to lose efficiency, but for 95% of South American routes it is the right tire.

Mud-Terrain (MT)

A much more aggressive tread and a hard compound, built for mud and severe off-road. On dry pavement it is noisy, less efficient and wears faster. On a heavy trail or in mud it is the best. For a conventional overland route through South America, with ripio, desert, steppe and a few wet stretches, it is overkill in most cases. If the trip involves many days of difficult trail, such as the roads of the Amazon or the Pantanal, then it starts to make sense.

Tire pressure: the adjustment most people ignore

The right pressure makes more difference than the tire type on a lot of terrain. The same rubber behaves completely differently at 36 psi and at 24 psi.

• On pavement: the manufacturer's standard pressure, usually 32 to 36 psi. There is no point saving by running lower: the result is uneven wear, excessive heat and higher fuel consumption.
• On ripio and gravel: drop to 26 to 28 psi. The tire gets more contact area, absorbs irregularities better and gets fewer flats. Top speed drops, which is natural, because on ripio you should not exceed 80 km/h anyway.
• On heavy off-road (rock, sand, mud): drop to 18 to 22 psi. Larger contact area, better traction, lower risk of a flat on sharp rocks. With pressure that low, avoid fast corners and high speed.

Important: when you get back on pavement, reinflate. Driving on pavement with a soft tire overheats it and can cause damage or a blowout. Keep a reliable gauge and a 12V compressor in the vehicle, a cheap investment with enormous value.

How many spares to carry

• A trip that is 100% pavement: one spare is enough.
• A trip with many ripio stretches: two spares is worth considering, especially if you are traveling alone. A double flat on severe ripio is not rare, since a sharp rock can catch two tires in the same pass. Whoever carries only one spare and gets two flats is left on foot, and that can get complicated.
• A long trip or one with very remote stretches: two full-size spares plus a temporary repair kit (rubber plugs) for simple punctures that let you drive to a tire shop.

Where to store them: the second spare, if the vehicle has no rear mount, goes inside the cargo area or strapped to the roof rack. A rear spare-tire carrier is worth the investment to free up interior space.

Tire repair kit: what to always have in the car

The basic kit fits in a small box and solves most simple roadside flats:

• Repair plugs (mushroom or spiral type): a temporary repair that lets you drive to a tire shop. Easy to apply, works on 90% of punctures in the tread.
• Rubber cement: comes with some kits.
• Insertion tool and reamer: the tools for applying the plug.
• 12V compressor: mandatory. Without it, even after the repair, you can't inflate the tire. Choose a model with a hose long enough to reach all the tires without moving the car.
• A jack rated for the load: the stock jack on many SUVs and pickups can't handle the load of a car full of travel gear. Check its capacity before leaving.
• The correct lug wrench: it sounds obvious, but check that the stock wrench loosens your bolts, because bolts torqued at the factory sometimes won't budge without an extension bar.

The rest of what goes in the car is in the complete packing list.

Wear and when to replace before the trip

A tire with less than 4 mm of tread depth should not go on a long trip with ripio. The wear indicator is built into the groove: when the rubber reaches the level of the arrow, it is at the legal limit and at the real safety limit.

Old tires with good tread but more than 6 years since manufacture (date printed on the sidewall, WWYY format, week and year) start to harden and crack internally. In high pavement temperatures with a heavy travel load, the risk of a blowout goes up. Replace them before leaving.

Before any long trip with ripio: rotate the tires (including the spare if it is a normal size) and check balance and alignment. An unbalanced tire on ripio vibrates far more than on pavement, and the vibration passed on to the vehicle speeds up suspension wear.

Use GT Overlander to plan your route before deciding on the tire. With the route drawn and the ripio stretches identified, you can decide much more precisely whether you need to switch to AT before leaving or whether the stock HT can handle what the route demands.

Frequently asked questions

Is it worth switching to AT before a trip through Argentina?

It depends on the itinerary. Argentine Patagonia with the Carretera Austral or Route 40 with ripio stretches: very much worth it. Buenos Aires, Mendoza and the vineyards on almost all pavement: the stock HT does fine. Map the ripio stretches of your itinerary before deciding.

Can I set different pressures for the front and rear axle?

The manufacturer usually recommends different pressures for front and rear (the rear is usually a bit higher, especially with a load). Follow the table on the driver's door of your vehicle. It specifies by load.

Does an AT tire raise fuel consumption a lot?

On average 5% to 10% more than an HT on pavement, depending on the brand and the profile. Factor that into the fuel budget for a long trip.

Are there tire shops on the Carretera Austral or at the Salar de Uyuni?

On the Carretera, in the larger towns (Coyhaique, Cochrane) yes. On remote stretches between towns, no. On the Salar de Uyuni circuit, there is one in Uyuni. On the stretch of the Bolivian lagoons (Laguna Colorada, Laguna Verde), there is absolutely nothing. That is where you most need two spares.

Can I use a "step-down" spare (smaller than the others) on ripio?

Technically it can get you out of a bind, but a smaller spare can't handle ripio for many kilometers. The differential and the suspension pay the price. Drive slowly and replace it as soon as possible with a tire of the correct size.

Wrapping up

The right tire is a silent safety item: you don't think about it while it is working. The wrong tire becomes the protagonist of the story at a moment when you definitely don't want a protagonist. Switching to AT before a trip with serious ripio is not an expense: it is the preparation item with the best cost-benefit on the whole list. And two spares in the trunk cost far less than a tow truck in the middle of the Bolivian Altiplano.