Unsurprisingly, for most Irish drivers, all tyres are the same, right? It’s a common misconception, since, at a glance, they can all appear the same as each other. But the reality is somewhat different, and important to be aware of. Why? Because if you inadvertently mix tyres, you could not only end up on the wrong side of the law, but also endanger your driver safety.
So how do tyres differ from each other?
There are two distinct differences between tyre types. The most obvious – because it can be seen if you look carefully – is tyre tread design. Different premium tyre manufacturers, such as Continental, create different tyre tread patterns. Each has its own view on how best the tread grooves can clear water from the road surface.
The other, more significant difference is tyre construction type. There are two main tyre build variations that car and van drivers can typically choose to fit – cross-ply and radial-ply. Each has its own benefits and strengths, but these characteristics should never be mixed and fitted together. And don’t forget, just as different tyre makers create their own tread pattern designs, the same is true of the compounds their tyres are made from. These differ significantly from manufacturer to manufacturer.
So what’s the difference, and why shouldn’t you mix cross-ply and radial-ply tyres?
A tyre is made up of many plies – layers – including rubber and cords of polyester, steel, or other textile materials – that, when fused together, give it the strength and resilience it needs to support your vehicle and let you drive safely.
Cross-ply tyres are diagonally overlapped along the length of the tyre crown (the top of the tyre), all the way down to the sidewall (the side of the tyre). This creates a solid, integrated unit, but means they are dependent on each other for structural integrity.
Radial-ply denotes that instead of forming an integrated crown and sidewall, the plies are arranged at 90 degrees to the direction of travel, or radially – in other words from the centre of the tyre, along its length – separate from the tyre sidewall. The two tyre elements are independent of each other, offering more flexibility, and also reducing the build up of heat within the tyre.
Each tyre has its own benefits, depending on the vehicle they’re fitted to, and the stresses from speed and weight loads they’re anticipated to experience. If you mix them, you won’t have a single, dependable stress tolerance across all your tyres, and this risks incurring tyre damage and having a blowout – increasing the chance of an accident.
For this reason, mixing cross-ply and radial-ply tyres across the same axle is illegal in Ireland.
Advantages of radial-tyres include:
- Improved steering and contact with the road
- Better driving comfort due to flexible sidewalls
- Reduced heat generation at high speeds
- Higher resistance to tread-related damage
- Lower rolling resistance, leading to reduced fuel consumption
Advantages of cross-ply tyres include:
- Significantly improved vehicle stability
- Tougher, more resistant to sidewall damage
- Cost less to manufacture, and subsequently to buy
- Ideal for transporting heavy loads, such as for vans and light commercial vehicles
Can I mix tyre tread patterns?
As with tyre construction types, mixing different tread patterns across the same axle is not permitted. The identical tyre model and tread pattern must be fitted for a single axle, though you can use different tyres (as long as they too match) on a separate axle.
However, tyre experts, including BestDrive and Continental recommend that the same tyres are fitted on all wheel positions of your vehicle. Why? Because then you can experience a consistent, dependable driving experience, without the risk of diminished performance that the mixing of tyres could potentially lead to.
Mixing tread depths isn’t a good idea, either
The same is true of fitting tyres with different tread depths across the same axle. If one tyre has more tread depth than the other, it’s going to clear water faster from the road surface, rather than at a consistent rate you get with two tyres of similar tread depth. This imbalance increases the risk of accident, since your vehicle has to cope with the different handling conditions that irregular water dispersion can cause. For this reason, tyre experts recommend that if you need to change a tyre (typically because of a puncture) do so for both tyres across the same axle.
Nor is mixing tyre sizes
Just as with mixing different tyre manufacturers, and tyre tread depths across the same axle, leading tyre experts like Continental recommend that you do not mix tyre sizes. Here’s why:
- Mismatched tyres can throw off your speedometer, giving you a false reading and making you unaware of how fast you’re driving.
- Having unequal tyres adversely affects steering, accelerating and general handling. There’s less grip and less control because steering feels sloppy.
- Unequal tyres can mean it takes longer for your car to get up to speed – dangerous if you need a sudden burst to evade danger – and, perhaps more importantly, it also takes longer for you to come to a safe stop.
- If one tyre is wider than the others, this will cause serious instability, particularly in wet or icy conditions.
- Long-term, you’ll be at risk of damaging your vehicle’s wheel bearings, and even destroying the clutch.
The exception to the rule
Some cars – for instance, some rear-wheel-drive BMWs and Mercedes-Benz – roll off the production line fitted with wider tyres on the rear wheels. It’s important to note that this doesn’t equate to a mismatch, because the same tyres are fitted on each axel, and the vehicle manufacturers have made a calculated, intentional decision to boost the traction on the rear driving wheels, so as to enhance driving dynamics. “OE” – Original Equipment – tyres selected have been designed specifically for this purpose.
Unsure about mixing tyres? Ask an expert – talk to BestDrive by Continental
Pop in to your local BestDrive branch and talk to our professionals for impartial tyre advice, including the no nos of mixing tyres. Our experienced team can provide you with expert fitting solutions, and more. You can find your nearest BestDrive branch at the top of this page.
BestDrive by Continental – You drive, we care.