SUV reliability & critical tyre replacement advice

Here’s one of the easiest ways to break your shiny new SUV, and be left completely out in the cold on warranty. (So easy to prevent.)


Once every two or three weeks I get a desperate e-mail from someone whose SUV’s all-wheel drive driveline has given up the ghost loudly and expensively.

They’ve had the whole nauseating conversation about the repair bill - and it not being covered under warranty. And when you trace the whole thing back to the root cause of the problem, it’s often what they did with the tyres: specifically, replacing them.

As in: They replaced two tyres and not all four. Which doesn’t sound like a big deal, but it is. At least on some all-wheel drive vehicles.

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The problem

This problem affects a heap of people, too, potentially, because softer SUV sales are booming, car sales are falling, and that means many people are ditching a conventional car and driving off in an SUV for the very first time.

A lot of those vehicles have all-wheel drive of one flavour or another - not all, but many of them do - and while 2WD is easy and familiar, like the car you’ve always owned, AWD is complex.

One of the operational prerequisites of many AWD systems is to have the same sized tyres on all four corners. Exactly the same size. As in: the same brand, with roughly the same degree of wear.

This is important.

See, when a vehicle drives here and there, especially in the city, all four tyres follow different paths (except when you’re going dead straight). Trust me on this. On every curve, all four tyres follow different paths.

And that means they’re all turning at different rates - because for any time interval they’re travelling different distances.

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And that means all the driveline components: the axles, the front and rear propshafts, limited-slip differentials on the cross axles or the transfer case - whatever other hi-tech malarkey is rotating ‘down there’ - they have to cope with this rotational mis-match.

There are viscous couplings and clutch packs, hydraulic actuators, servo motors - it’s mechanically complex.

And these systems do cope with turning at different rates. Up to a point. But if you throw in different rolling diameters on the tyres, by mixing them up - two new tyres of Brand A with two semi-worn tyres of Brand B. That can be enough to tip the driveline over the edge and break something prematurely.

Think about it like this: There’s about 6.5 millimetres of available tread between brand new and worn out, on an average tyre. That’s 13 millimetres on the diameter - just over half an inch.

So if you’ve got the car at 110km/h on the freeway, with two new tyres and two worn tyres, the new ones are rotating two per cent slower than the old ones, for hours on end. And this is a recipe for accelerated wear and tear. According to carmakers.

More on AWD systems & tyre replacement >>

How carmakers sidestep warranty claims

It’s a systematic vulnerability - an easy way to break something expensive. Rebuilding a limited-slip diff in a transfer case is a big job, and the manufacturer may well point you to page 783 of the owner’s manual where it says: ‘All four tyres must be replaced at the same time’.

And, I sympathise: if you are the unwitting victim here, it just doesn’t seem very fair.

This process, from the vulnerability to the breakdown to the manufacturer’s denial of a warranty claim leaves you - kinda - out in the cold legally. Because, hey, you failed to comply with the owner’s manual.

It’s unfair, in my view, because who reads every page of the manual? If this is so important, why aren’t you told in a more proactive way? Why isn’t there a training course, if vehicles are that complex, or at least an instructional video online to help you out here?

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The answer is - clearly - because the sales guy wants to sell you the vehicle, not give you a bunch of reasons to be terrified of owning it.

They do the same thing with diesels. Hardly any dealerships will spell out the operational prerequisites for regenerating a DPF. You have to get out on the highway once a fortnight, otherwise this fine vehicle might shit itself.

Salesmen generally don’t say that.

Not when the mother ship demands that they sell ‘X’ number of diesels every month.

So it seems to me that many carmakers are doing owners a disservice by not getting these kinds of serious operational imperatives front and centre before purchase.

And of course I hate them engineering a convenient out for themselves by telling you, hey, it’s in the fine print in the manual - which statistically, nobody reads.

They know this. But it works for them, bureaucratically. I mean, ‘Here it is, in black and white, your worship.’ Case closed. Next!

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The solution: regular tyre rotation

So, here’s what you do to sidestep this particular mechanical takedown:

It’s dead easy, too. Every 5000 kilometres, have your tyres rotated. And don’t get cute with me here: I know tyres rotate. What I mean is, get your mechanic to change each tyre’s position on the vehicle. In a systematic way.

This is going to depend on the kind of tyres you’re running (because, for example, directional tyres cannot be changed side-to-side without removing them from the rim and turning them the other way around. Trust me on this.)

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So, unless you know exactly what you’re doing and you have too much spare time, get the mechanic to do it for you. It’s a small expense. He’s got a hoist, and all the right tools. It only takes a few minutes.

What this does is even out the wear - because different positions on the vehicle wear more severely than others. Fronts generally wear more than rears, because they drive and steer and scrub more, and in right-drive markets like ours, front left tyres wear faster than front rights - especially in cities.

Details on tyre rotation at Wikipedia >>


This way, at the very least, all four tyres will be essentially wear evenly, and all be worn out at the same time, and you won’t be tempted to replace only two because the other two seemingly still have some decent life left in them, opening the door to transmission meltdown.

Which is like sailing to that part of the ocean labelled: ‘Thar be dragons’. Don’t go there. You wouldn’t like it there.

It’s prevention versus cure. And remember: This report applies to vehicles with all-wheel drive - the softer kind of SUVs, generally. They can be Symmetrical AWD like Subarus or on-demand AWD like most of the rest of the competition.

It’s generally not such a big deal for most utes and other agricultural, hard-core off-roaders with serious, hardcore off-road ability. These are generally 2WD on high-traction surfaces.

So if you select ‘2H’ for normal driving, this is not so important.

But simple tyre rotation can save you thousands in broken whatever on an AWD vehicle - and it’s not a bad idea to rotate the tyres on most other vehicles as well, if you want to maximise the life of any given set of tyres.

So make friends with your local mechanic. He’s a real asset here.

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