Car 101: how to avoid potholes and what to do if you can’t

Potholes have been causing havoc across the country, with barely a week going by without several stories of chaos and damage being caused by them. But what are they, why do they happen and, more importantly, how do you avoid hitting them? And what do you do if you can’t avoid them?

Well, we’ll get to that, but firstly, potholes begin life when water seeps through cracks in the road. While roads are usually well compacted by rollers when under construction, it is pretty much impossible to compress the asphalt totally uniformly, so water will always find a way in.

In colder climates, that water can freeze and push sections of road upward, with the eventual thaw resulting in unsupported pockets, while in warmer climates, soil erosion under the road results in weak spots. Add to this the continual pressure of traffic driving over these weak spots and they will eventually collapse, giving life to brand-new pothole, all ready and eager to destroy your tyre. Or, at the very least, make your ride worse.

No matter how well a road is made, if the surface is asphalt, the water will almost certainly find its way in. If it is poorly made, then it will get in sooner and far more frequently.

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And in a country like New Zealand that is relatively ‘young’ in a geological sense, the underlying land is far more active and unstable, with the resulting movement meaning more cracks appear. Which means more potholes.

So how do you avoid a pothole?

The same way you avoid any other obstacle on the road – by paying attention to what is in front of you – but even then it isn’t quite that easy.

Potholes are tricky little buggers, being generally the same colour as the rest of the road, they often just look like a wrinkle or other slight imperfection in the road surface, so they do demand that you be on top of your observation game.

They can also disguise themselves as innocent puddles in the rain, making their sharp edges seem far less severe, so there will be occasions when it is simply impossible to see a pothole.

How badly can a pothole damage your car?

It can be anywhere from “not at all” to “not drivable”. The best-case scenario is that your vehicle is totally undamaged, but a big impact can render your vehicle undrivable. Bent rims and damaged tyres are the most likely things that will stop you from continuing down the road – particularly if you damage two of them.

If the pothole is big enough – or your speed is high enough – you may have damaged something more substantial under the vehicle, like bending a tie rod on your suspension or cracking the sump. In which case, you are in for a wait for a tow truck.

How do you minimise the possible damage when you do hit one?

Firstly, if it is raining and puddles have formed, you should have already slowed down for the conditions (generally speaking, if you hit a pothole hard enough to damage your tyre or wheel in the rain, then you were probably driving too fast for the conditions anyway…), but if you are on a stretch of road known for potholes, then dropping your speed even more is advisable.

This gives you a better chance of seeing the hole, as we as minimising the potential damage if you hit one.

Make sure your tyres are properly inflated. While you should always do this anyway, tyres that are under-inflated don’t absorb the impact as well and make it far easier to damage the wheel rim, while tyres that are over-inflated will put more pressure on the tyre sidewall, increasing the risk of a blowout.

Keep your steering wheel straight when you hit the pothole – turning while going through a pothole puts more stress on one side of the tyre and sudden movements can not only potentially throw your car off balance, it could cause other road users to panic too.

If you can, release the brakes just before you hit the pothole. Braking transfers the car’s weight to the front of which compresses the front suspension. This leaves less suspension travel when the wheel hits the pothole, raising the risk of damage and making the impact worse in the cabin as well.

What should you do after hitting a pothole?

If it is a big impact, the first thing you should do is gently pull off to the side of the road and come to a halt in a safe location. Check your instrument panel for any warning lights – if anything has flashed up, that will be your first sign something is damaged.

As you pull over listen for any irregular noises coming from your car – dragging, clunking or the instantly recognisable sound of a flat tyre will all give you a clearer idea of any potential damage.

Inspect the wheel for cracks or dents. Driving on a cracked rim poses a safety risk to you and others road users, with the potential for the wheel to collapse altogether. If the wheel itself has no visible damage, move on to the tyre.

The tyre will have absorbed most of the impact and the sidewall – the thinnest part of the tyre – would have flexed quite dramatically. Depending on how hard you hit the pothole, your tyre ay already be flat, in which case you aren’t going anywhere on it. Listen out for any telltale sounds of air leaking as well.

If the tyre is still inflated and not leaking air, you should be good to go, unless you see a bulge or bubble on the sidewall. This means the tyre’s integrity has been compromised and it could let go at any time. Don’t be tempted to try and drive on it and change to your spare immediately before driving off.

If your tyres and wheels are okay, then you should check under your vehicle for any visible damage. Cracks or damage to anything like the exhaust system or underbody protection are okay to drive with, but if you see anything more substantial – or any visible damage to the suspension or steering – you should wait until help arrives.

Also, if you see any oil or other type of fluid leaking (other than water from your air conditioning, that is), you should not drive the car as you will almost certainly damage the engine by continuing.

If everything looks okay outside the car, then you can hop back in and do a simple check of your steering alignment by centring the steering wheel and (assuming you’re in a safe location) drive slowly straight ahead at around 10 to 15kph with your hands loosely holding the steering wheel.

If it begins to turn in any direction and pull to one side, you will need to take your vehicle to a mechanic. Depending on how bad your alignment is off, you should be able to drive the car to get it looked at, but if it shudders or pulls dramatically to one side, you shouldn’t drive anywhere.