Newsletter - July 2013

Potholes and the Effect On Tyres

It’s been estimated potholes cost Irish motorists hundreds of thousands in repairs annually. But I’ve got some top tips on how to limit damaging a tyre in a pothole and inspecting for potential issues if you are victim of one. To realise why hitting a pothole can have such a serious effect on a tyre it’s important to understand its composition. They’re not just shaped rubber; there are at least 25 structural parts and 12 different compounds inside them. The body ply is made from a fabric such as polyester or Rayon and wraps around the tyre at 90 degrees to the direction of travel. It forms the base that the tyre is built on and gives it structural strength. Essentially it’s the tyre’s skeleton.

Imagine you hit a pothole with just one side of the tyre, which is the scenario that inflicts the most damage. For a split second, the forces going down through the tyre are all focused on the one part of the sidewall that’s hit the furthest edge of the hole as your wheel exits it. These forces push the wheel rim down and pinch the sidewall – we call it a rim pinch. This can result in breaking the cords in the area of impact and causes a weakness in the body ply. People often go through potholes and then immediately stop to inspect their tyre. Very often it is difficult to detect any evidence of damage and they’ll think they’ve got away with it. But a damaged body ply in a tyre is like a weakness in a central heating pipe: it probably won’t leak until the system is hot and running under pressure and even then it may take some time to manifest itself. With the tyre, as you pile on the miles, the ply will keep flexing, and then at some point it may give way.

In the most extreme case there’ll be an instantaneous deflation – a blowout. More usually, you’ll get a bulge in the sidewall first. This is where the body ply has become weak and you just have a thin layer of rubber preventing air loss. Unsurprisingly, bulges make the tyre illegal and an NCT failure point because they can give out at any point. It’s well worth looking out for damage and it’s sensible to inspect your tyres on a regular basis. Remember to look on the inside as well. You don’t have to get dirty: simply lay down a groundsheet or newspaper and turn the steering to full lock, then use a torch to help inspect the inner wall of the tyre. It could save you from a failure at high speed.

And how do you avoid pothole damage? It’s impossible to scan the entire road surface all the time. But if you spot one at the last moment, you can limit the consequences. If your car’s wheel and tyre strike the hole head on, both sides of the tyre will go into the dip and the forces will be spread evenly across the tyre and both its sidewalls, giving you the best possible chance of minimising the damage.

See more at: http://blog.conti-online.co.uk/continental-tyres-tips-for-limiting-pothole-damage