Tyres for powerful SUVs and 4WD models have to master more challenges than their counterparts for “normal” cars. “When we compare the vehicle data, we see that the big, fast models ask more of their tyres,” explains Continental tyre development engineer Andreas Schlenke. “In terms of weight alone, an SUV tips the scales at one third heavier than a normal car, so the tyres need a higher load capacity. These are XL tyres (XL = Extra Load), a load range developed to offer higher load capacity than standard, not least with SUVs in mind. Then we have to allow for the vehicle’s higher center of gravity, longer suspension travel and a greater track width than in smaller cars. So when we’re developing these tyres, we need to invest more time and effort to ensure safe braking and precision handling. After all, in the more powerful SUVs we’re talking about top speeds not far below those of high-end sports cars.”
According to Schlenke, “it’s a bit of luck for developers” that only a small proportion of SUVs and 4WD models are actually driven off-road. Just delivering the safety-relevant properties, low rolling resistance and good ride quality is challenging enough. “On top of that, off-road driving calls for a chunkier tread pattern with good self-cleaning properties, plus cut-and-chip protection and strongly reinforced sidewalls,” he says, describing the tyres. This type of construction is less than ideal for fast highway driving because, out on the road, the chunky lugs that interlock with scree and stones on rough terrain cannot put down enough grip to handle fast cornering and braking from speed. “That’s why real off-road tyres bear the M+S symbol,” says Schlenke. “That’s the hallmark of a specialist – after all, M+S stands for mud and slush.” So before buying tyres, owners of SUVs and 4WD models should think carefully about where they are going to be driving their vehicles and choose their tyres accordingly.
Schlenke also warns against winter driving on chunky M+S tyres that do not bear the three-peak mountain snowflake symbol: “Four-wheel drive tends to suggest strong grip when moving off on wintry roads,” he says, “but with off-road tyres that deliver inadequate braking distances and poor lateral guidance on snow and ice, you will only put yourself and other road users at risk.”