So it’s snowing – so what? Many drivers still stick with their summer tires through the winter as well. In an interview with VisionZeroWorld, Continental tire expert Denise Ewald explains the importance of seasonal switches, analyzes the case for all-season rubber and looks at why tires are getting smart.
Ms. Ewald, many drivers still aren’t switching over to winter tires in the fall. They’re thinking “It won’t snow all that much, I’ll be alright.”
I can only advise against this as a course of (in)action, unless you really are planning to put your car into hibernation over the winter months. Driving on summer tires in wintry conditions is against the law in some countries. And the fact is that summer tires cannot work to their full potential in winter, which means drivers are subjecting themselves and other road users to needless danger.
But as the person responsible for development of summer tires at Continental for the key European market among others, shouldn’t you actually be happy that people trust your summer tires?
Of course I’m pleased there are such high levels of trust in our summer tires, absolutely. But only when they’re used in summer. In winter we need to let our colleagues in winter tire development take the plaudits (laughs). Seriously though, driving on summer tires in cold winter temperatures is hugely negligent.
What are the telltale signs of a wrong tire choice in winter?
Using summer tires in winter significantly increases braking distances and cannot generate enough grip in snowy or icy conditions. That obviously goes hand in hand with a sharp drop-off in safety. When the subject of switching tires comes up, we often talk about “wintry conditions”. That doesn’t necessarily mean the roads are covered in ice or snow, but quite simply that the temperature is below seven degrees Celsius. At that point, winter tires become the better option, the safer option. Winter tires have a different rubber compound that retains its elasticity in cold temperatures. That’s what allows them to deliver their full braking effect.
On the flip side, what are the drawbacks of continuing to drive with winter tires in summer (saving the hassle of swapping tires again)?
That’s not a good idea either. The tread on winter tires has more sipes and a softer rubber compound. When you’re driving on dry, warm road surfaces, this has an extremely adverse effect on braking distances and handling characteristics. And your vehicle will also burn more fuel. It’s not hard to remember the basic rule: summer tires in summer, winter tires in winter.
And what about all-season tires?
All-season tires are a compromise. They have to work well on both dry roads in summer and on snow or ice in winter. That’s a conflict of interests which can only be partially resolved; all-season tires cannot offer all the positive attributes of summer and winter tires in full. Having said that, there are circumstances in which the compromise that all-season tires represent can offer a genuine alternative – if you spend the year driving mostly in urban areas in regions with temperate climates, for example. But when a spell of seriously wintry weather arrives, winter tires are a must. If you’re using all-season tires, you should leave the car at home when road conditions get tricky.
For many drivers, the design, equipment level and performance of their car are what counts. Tires come further down the priority list.
As a tire developer, that’s not what you want to hear, of course. It’s true, though; tires are a frequently under-appreciated part of a car’s make-up. And yet they provide the sole point of contact between the car and the road, which means they are a key contributor to occupant safety. Many users are not really aware of their tires because you can’t see them when you’re on board.
Continental has set its sights on an accident-free future. What part do tires play in this vision?
Tires have an absolutely critical part to play here; as I said before, they are the only part of a vehicle that’s in contact with the road. All the safety systems in the world will be no use if the tires can’t effectively transfer the forces generated by the anti-lock braking system, for example, to the road. But of course turning Vision Zero into reality involves more than just the tires.
So when you’re developing tires, do you liaise closely with colleagues developing driver assistance systems, for example?
It goes without saying that we design our tires to interact effectively with safety systems such as ABS and ESP. So we naturally work closely with our colleagues in other divisions who develop the driver assistance systems. Road safety obviously benefits if the tires and driver assistance systems are geared to one another from the development stage and then interact to perfection.
What makes a tire a good tire?
There’s no such thing as the ideal tire for all eventualities. A tire is good if it meets the requirements of a vehicle and the customer. But these requirements can be very different. In a small compact car, a more sporty vehicle or a hybrid or electric model, the different applications mean different demands on the tire. And it’s the ability of a tire to fulfil its specific brief that determines whether or not it’s doing a good job. But there is, of course, a rule of thumb: Good tires offer good braking attributes on all surfaces as well as precision handling. And looking ahead, the intelligence of a tire is also set to become more important.
By that I mean that sensors in the tires will tell the vehicle what sort of surface it’s driving on, for example – and adjust the tire pressures accordingly. Last year Continental presented two innovative tire concepts. First there is ContiSense, where tire sensors measure the tread depth and temperature, and warn the driver in the event of danger. Interestingly, the data transfer here is via electrically conductive rubber. The second concept is ContiAdapt, which enables tire pressures to be adjusted while on the move to modify the size of the contact patch. This way, the tires can adapt very effectively to the different challenges of driving on slush, snow or ice.
What kind of “super-ingredient” would need to be discovered or developed to create the perfect tire for all scenarios?
I don’t believe in super-ingredients. But if I did, and I knew what the super-ingredient was, then we’d already be using it (laughs).