In recent years the 4x4 market has expanded to become the fastest growing sector of new vehicle registrations, in 2002 the demand for 4x4 tyres was 250% of that for 1997. Gone are the days when a 4x4 vehicle meant driving an ex-army vehicle with no heaters / wipers / performance etc. Today's 4x4 vehicles are some of the most sophisticated on the road.

Even manufacturers that many years ago may not have considered a 4x4 vehicle in their model line-up are selling as many as they can build - BMW X3 and X5, Porsche Cayenne to name but a few. Most of these "new generation" 4x4's come equipped with equipment such as cruise control, climate control, active suspension (to name but a few) as standard. Probably the biggest improvement is to be seen in the vehicle performance - for instance the Porsche Cayenne Turbo puts out 450bhp with 620 nm of torque, and will easily outperform the vast majority of cars of the road.

To cope with the extra power and performance of these new vehicles the tyre requirements have changed dramatically. In the past most 4x4 vehicles were equipped with either 15" or 16" wheels and fitted standard (80 series) or possible 70 series tyres with either "S" (113mph) or "T" (118mph) speed rated tyres. Again if we take the Porsche Cayenne Turbo as an example the standard wheels fitted are 8Jx18 with 255/55R18 Y rated (186mph) tyres. Again with these vehicles there is always the option to upgrade wheel and tyres to 20" or even 22" and above.

In order to accommodate the extra requirements of the vehicle manufacturer in relation to the performance of these vehicles the tyres have had to change dramatically. Most manufacturers break down their range of 4x4 tyres into different categories dependant on the type of vehicle and also the usage of the vehicle. For instance, a high performance 4x4 used predominantly for on-road application will require a relatively quiet, comfortable tyre compared to an older type 4x4 that spends the vast majority of its life working off-road. Categories can usually be described as follows:

• On-Road
• Off-Road
• Winter

The development and diversification of the 4x4 tyre market requires that these 3 main categories be further split into sub categories as below:

• Performance - high performance, 100% on-road use
• Luxury - Top end luxury 4x4 vehicles
• Terrain - On/Off-road use

Winter tyres are specialist tyres designed mainly for the European market and are not usually in great demand in the UK. Winter tyres are designed to run at very low ambient road temperatures and will have very different characteristics and technologies to "normal" 4x4 tyres including ice compound tread rubber, special sipe arrangements and even holes in the tread to allow for studding of the tyre for ice use. Below are typical examples of winter tyres (Bridgestone and Michelin) specifically designed for snow and ice conditions.

The market tends to split 4x4 vehicles into 4 categories:

• SUV's (Sports Utility Vehicles) - Freelander etc
• Sports/Luxury Vehicles - BMW X5, Porsche Cayenne etc
• Pick-ups (Functional/Leisure) - Ford Ranger etc
• Cars/Vans with Off-Road Capabilities - Subaru Forester, Renault Scenic 4x4 etc

Tyre Categories

On Road: Performance

4x4 tyres designed primarily for on-road use are now more popular than ever. Vehicles such as BMW X5, Porsche Cayenne, Volvo XC90 to name but a few are demanding performance from a tyre previously only required for high performance road cars. These tyres need to deliver car-like performance whilst fitted to heavy 4x4 vehicles. Tyres for vehicles such as these now include such features as directional tread, high performance tread compounds and many others.

Below are 3 examples of high performance on-road tyres. You can clearly see the aggressive, directional patterns that give the tyre its excellent dry and wet grip although off road and heavy snow performance will be limited - not a major problem with vehicles used predominantly on-road.

Bridgestone HP680

Michelin Diamaris

Goodyear Wrangler F1

On Road: Luxury

Luxury 4x4 tyres are, as are the performance tyres, designed to be used predominantly on-road. The main difference is that, due to the type of vehicle to which they are fitted, they need to offer a higher degree of performance whilst offering a similarly high degree of comfort - low noise and vibration. Tyres for this sector of the market (Lexus RX etc) will tend to have a less aggressive tread pattern, usually with smaller tread blocks designed to reduce noise and vibration and provide a quieter, more comfortable ride.

Bridgestone D683

Michelin Syncro

Goodyear Wrangler

On-Road: Terrain

Although on-road terrain may seem to be something of a contradiction, these tyres are designed for vehicles that, although used predominantly on-road DO have the occasional off-road experience. They are a tyre that will give a relatively quiet, comfortable ride whilst used on-road but also possess a better off-road ability that the two previous categories.

Bridgestone D684

Michelin 4x4 A/T

Goodyear Wrangler SRA

Off-Road

Performance requirements for an off-road tyre will, obviously, differ greatly than those for an on-road. Comfort and noise, whilst still being relevant, are not the number one priority. Whereas an on-road tyres' main requirement is good dry surface performance and comfort, an off-road tyre will be more concerned with traction in a variety of conditions. These may range from dry, dusty surfaces to deep mud and anything in between. Most major tyre manufacturers will produce a range of tyres suitable for these different conditions. Tyres for off-road use will include such features as heavy, rugged tread patterns, stronger carcass construction (to resist the heavy impact and deflection associated with off-road use) and cut resistant tread compounds.

Off-road tyres are usually divided into two categories - All Terrain and Mud Terrain. All terrain tyres usually have a heavy tread pattern (compared to on-road tyres) and a robust tread construction to resist impact damage whilst working of road. Mud terrain tyres will feature the heaviest tread pattern of all, possibly directional to assist in the self-cleaning capability of the tyre. Obviously with such a heavy, aggressive tread pattern, mud terrain tyres, whilst useable for on-road driving would not be a recommended fitment due to the relatively high levels of noise and vibration - think of a tyre from the rear of a tractor!

Off-road All Terrain v Mud Terrain (Bridgestone):

All Terrain

Mud Terrain

Conclusion:

In order to obtain the best possible performance form a 4x4 vehicle it is essential to determine which tyre is the correct one for your vehicle. If in doubt take a look at what the vehicle manufacturer has fitted from new. They will know what sector of the market a particular vehicle is aimed at and will fit tyres accordingly.

High performance on-road tyres such as those listed previously will perform very well on the surface they are designed for - take them off road into heavy conditions and the off-road capabilities will be put severely to the test. The vehicles that these are designed to be fitted to, although capable of working off-road will be limited in their off-road capabilities.

Off-road tyres, in particular Mud Terrain tyres, perform superbly in all conditions encountered off the beaten track. They are very popular with off-road 4x4 clubs who will use them for leisure and competition days. Drive any long distances on the motorway with these tyres fitted and you will soon be aware of the reasons they are not recommended for regular road going use.

Winter tyres, as previously discussed are specifically designed for very low temperature use and, due to the relatively high ambient temperatures in the UK are not so popular although there is a limited market in the very North of the country.