Nobody replaces tires early for fun. They are one of the biggest wear bills on a truck, so the honest question every owner eventually asks is the same one: how long can I actually run these before they need to go. The legal answer and the safe answer are two different numbers, and out here, where most of us split time between pavement, gravel, and eight months of weather, the gap between those two numbers matters more than it does almost anywhere else. Here is the straight version we give at the counter, and if you would rather just have us measure and give you a yes or no, book a tire inspection with our service department and we will put a gauge on all four in a few minutes.

Key Takeaways

• The legal line is 1.6 mm (2/32 of an inch). The Manitoba Driver's Handbook says to replace tires when tread is below 1.6 millimetres, and a Manitoba safety inspection fails a tire at that point. Transport Canada's wear bars sit at essentially the same level: when the tread is flush with the bars, the tire is done.
• The safe line comes sooner. Braking on wet pavement falls off well before the legal minimum, and for snow, tires worn close to 4 mm (5/32) should not be relied on. Around half worn is when winter grip quietly leaves.
• The quarter test is the free check. Insert a Canadian quarter in the groove with the caribou's nose pointing down. If the tip of the nose stays covered, you have more than 6/32 left. Do it monthly, in a couple of spots per tire.
• Age retires a tire even with tread left. Michelin recommends replacement ten years from the date of manufacture regardless of condition, with a professional inspection every year after year five. Rubber ages out, not just wears out.
• Gravel changes the math. Chip and cut wear on stone means a prairie truck's tires often need replacing before the wear bars say so. Cuts, chunked tread blocks, and sidewall damage are replacement triggers on their own.

The Legal Number, and Why It Is Not the Real Number

Every tire sold here carries built in wear bars, small raised ridges running across the grooves. Transport Canada's guidance is plain: when the tread is worn down to the level of those bars, about 1.6 mm or 2/32 of an inch, the tire must be replaced. The Manitoba Driver's Handbook uses the same line, and a Manitoba vehicle safety inspection fails a tire below 1.6 mm. So that is the floor. Below it you have no legal margin and, more to the point, almost no rubber doing any work.

But treat 1.6 mm as a deadline, not a target. Tread depth is what evacuates water on a wet highway and bites into snow. As depth drops, wet stopping distances stretch long before the tire is illegal. That is why the practical advice is different from the legal one: on a truck that tows, carries weight, or sees Manitoba winter, start planning replacement around 4/32, and do not push a set into a second winter below that. Transport Canada itself says tires worn close to 4 mm (5/32) should not be used on snow covered roads.

Winter tires have their own line. A winter tire below roughly 3.2 mm (4/32) has lost the tread depth that made it a winter tire. It may still be legal. It is no longer doing the job you bought it for.

The Checks You Can Do in the Driveway

The quarter test. Insert a Canadian quarter into the tread groove with the caribou's nose pointing down. If the tip of the nose is covered by tread, you have more than 6/32 of an inch left, which is healthy. Check a few grooves across the tire, inside edge, centre, and outside edge, because uneven wear between them is its own warning: it points at pressure or alignment problems that will eat the new set too. If one edge is bald while the centre looks fine, get the alignment checked before you spend money on tires.

The monthly walk around. Transport Canada recommends checking tires at least once a month: pressure when cold, and a look for cuts, cracks, bulges, embedded stones or screws, and uneven wear. Thirty seconds per tire, and it catches most problems while they are still cheap.

The date code. Every tire's sidewall carries a DOT code ending in four digits, the week and year it was built. A tire marked 3520 was made in the 35th week of 2020. After five years, have tires professionally inspected annually. At ten years from that date, Michelin's guidance is to replace regardless of how the tread looks, because rubber hardens and loses grip as it ages even when the tire has barely worn. That ten year rule catches a lot of low mileage trucks and stored seasonal sets that look fine.

What Manitoba Actually Does to a Set of Tires

The tread depth rules are national. The wear rate is local, and ours is faster than the brochure assumes.

Gravel chips and cuts instead of wearing. A truck that runs grid roads does not wear its tread down evenly like a highway commuter. Stone works the tread blocks, chipping edges and opening small cuts, and an aggressive tire on gravel can look ragged with plenty of depth left. Chunked or torn tread blocks are a replacement trigger on their own, whatever the gauge says, because a damaged block is a block that is not gripping and a place for further tearing to start.

Heat and load in summer, cold in winter. Towing in July heat runs tires hot, and heat is what turns a marginal tire into a failed one. Then the same set spends winter cycling from a heated shop to 30 below, which is exactly the aging that cracks rubber over the years. Sidewall cracking, bulges, or blisters mean structural damage, and Manitoba's guidance is blunt: replace, do not monitor.

The seasonal changeover is your inspection. Most of us swap between winter and summer sets anyway, and the changeover is the natural moment to measure both sets and look them over properly. If you run studded winters, remember they are illegal in Manitoba between April 30 and October 1, so the spring swap has a hard date on it. Rotation matters too, because it is what keeps a set wearing evenly enough to replace as a set instead of in expensive pairs. Our tire rotation guide covers that schedule.

When the measurement says it is time, our parts department can quote the right tire for how your truck actually works, highway, gravel, or towing, and the service centre mounts, balances, and aligns so the new set lasts the way it should.

FAQs

At what tread depth should truck tires be replaced?

The legal minimum is 1.6 mm (2/32 of an inch), the level of the built in wear bars, and a Manitoba safety inspection fails a tire below that. For practical safety, plan replacement around 4/32, especially before a winter, because wet and snow grip fall away well before the legal line.

How do I check tire tread with a quarter?

Put a Canadian quarter in the groove with the caribou's nose pointing down. If the nose tip is covered, you have more than 6/32 of tread. Check several grooves on each tire and repeat monthly.

Should I replace all four truck tires at once?

Ideally yes, especially on a four wheel drive truck, where mixing significantly worn and new tires makes the driveline work against itself and leaves grip uneven. If the fronts and rears are wearing at different rates, regular rotation is the fix that lets the set retire together.

Do tires expire even if the tread is good?

Yes. Rubber ages regardless of mileage. Have tires inspected annually once they pass five years old, and replace at ten years from the manufacture date on the sidewall even if tread remains.

How long do truck tires last in Manitoba?

There is no honest single number. Highway driven trucks can see long tire life, while gravel and heavy towing can cut it dramatically, and age can retire a low mileage set first. The monthly check and the seasonal changeover measurement are what tell you where your set actually is, and we are happy to measure it for you.

The Bottom Line

Replace truck tires at 1.6 mm because you legally must, around 4/32 because you sensibly should, at ten years because rubber ages out, and immediately when a sidewall bulges or tread blocks tear, because those are not wear, they are damage. Out here the gravel and the seasons push every one of those triggers closer, so the monthly quarter test and one honest measurement at each seasonal changeover are the whole discipline. If you want the numbers without the guesswork, book with our service department and we will measure all four, tell you what is left, and give you a straight answer on whether they will make another season.

Tyler Dunn, Dunn Ram Trucks, Portage la Prairie