Change the tyres on your 4×4 and enjoy a whole new experience!! So what is wrong with the standard tyres on your 4×4 vehicle? Nothing at all is the answer. The manufacturer of your vehicle has worked closely with the tyre manufacturer to ensure the best level of performance and comfort is achieved to appeal to the demands of the average motorist.
The average motorist spends most of their time on the road, so the tyres fitted to a vehicle at the factory are intended to provide a small amount of off-road ability, with the main priorities being stability at speed, good steering and low noise on the road. Some off-road tyres can perform very well on the road but they are by nature slightly noisier and the ride can be less comfortable. This varies according to the specific tyre and the technology used in the tread design.
So these perfectly good road tyres are not the ideal product for those motorists who have more individual needs. This includes owners of ultra high performance vehicles who need the highest levels of grip possible, or 4×4 owners that need to venture off road.
Whether you are venturing off road to enjoy leisurely jaunts across green lanes or scrambling across specific terrain, for work or sport, correct tyre selection suddenly becomes very important and a whole host of new factors need to be considered. Remember that road surfaces are tarmac. Off-road surfaces can be hugely different, from damp fields, peat bogs to chalky ridges.
MAKE SURE YOU GET IT RIGHT
Selecting the wrong sized tyre with an unsuitable tread design can spell danger as well as being costly on your wallet and will reduce tyre performance. For example fitting a mud terrain tyre to your vehicle will give excellent levels of grip in extreme off road conditions, but will cause a massive increase in braking distances and reduce steering responsiveness.
It is not always possible to fit the most appropriate tyre for your needs by using the original tyre size fitted to the vehicle. There are certain proven conversions for 4×4 vehicles that our experienced 4×4 technicians can advise you on. If you need help with tyre selection then allow our technical team help you make selecting the right kind of tyre a painless job. We can also source your chosen tyre and arrange fitting at a trusted independant tyre dealer.
It is strongly recommended that tyres on 4×4 vehicles are used in identical sets of 4, (same size, make, pattern, load index/speed symbol). The vehicle manufacturers’ recommendations should also be followed.
Off Road Grading Index (ORGI):
Choosing the right tyre can be difficult. Every tyre a manufacturer makes is designed with specific strengths in mind. How well it performs to these strengths depends on the construction methods, materials used and the technologies applied in the design and testing process. 4×4 tyres by definition introduce even more variables than these into the mixing pot.
To make it a little easier to select the right tyre, a good place to start is to think about what you intend to use your 4×4 for. If you are intending to use your vehicle off road then you need to determine just how extreme the terrain is likely to be and how much time you are likely to spend on it. The ORGI guide assigns every 4×4 tyre we feature with an off-road competency rating between 1 & 10. From here it is possible to disregard certain tyres as unsuitable and narrow the field of selection down.
Note that this is a subjective rating. Each tyre is assigned its level of off-road ability according to a combination of our theoretical and practical experience, coupled with manufacturer and consumer feedback.
Also, note that generally the more aggressive the tyre, the less competent it is on the road. Although the very best tyres like B.F.Goodrich will still have good road manners, you will find that tyres generally become noisier when they are more off-road biased.
Understanding Tyre Sidewall Markings:
1. Tyre Size Designation
On all 4×4 tyres there will be an LT in front of the tyre size if the tyre is of a reinforced construction. LT means light truck (reinforced). If there is a ‘P’ or no lettering at all, then it will be a Passenger tyre type. We strongly recommend fitting the same type of tyre on all four corners of the vehicle, fitting different types of tyre on the same vehicle can cause issues with the vehicles handling characteristics. The ‘235’ is the nominal width of the tyres cross section in millimetres. The ‘85’ is the ‘aspect ratio’ – the ratio of the side wall height to the cross-section width. The ‘R’ stands for radial-ply construction. The ‘16’ stands for diameter (in inches) of the wheel that the tyre is designed to fit. Always ensure that the tyre fitted has the correct or higher load/speed rating as specified for the vehicle. It is not recommended to mix tyres with different load/speed ratings on the same axle.
2. Indicates exterior sidewall on asymmetric tyres for fitting purposes.
3. Load Pressure Information
(Not required in the UK).
4. Brand Name
5. Tyre Construction Details
(Not required in the UK).
6. European ECE Type
Approval mark number.
7. Load Capacity Index
Shows the maximum weight the tyre can carry at the speed indicated by its speed rating.
8. Speed Category Symbol
A letter which indicates the speed at which the tyre can carry the load corresponding to the Load Capacity Index. Common speed ratings are ‘Q’,’S’, ‘T’, ‘H’, ‘V’, ‘W’ ‘Y’, and ‘Z’.
9. Country of Manufacturer
10. Commercial Name & Identity
11. Location of Tread Wear Indicators
(Markings not on all tyres) Tread wear indicators moulded into the base of the the tread are set at the minimum legal depth of 1.6mm.
Off Road Driving Guide
Four-wheel drive vehicles can master seemingly impossible terrain with consummate ease. Conversely, they can get hopelessly stuck in a flat field of grass. Whilst the vehicle and the choice of tyre are absolutely critical to successful off roading, it is ultimately the skill and competence of the driver that decides between an enjoyable drive and embarrassing failure. Here we explain the essential basics to put you on the right track to tackle routine off-road situations with confidence and in safety.
KNOW YOUR VEHICLE
The starting point is to thoroughly familiarise yourself with the vehicle by consulting the owners manual. Some vehicles are permanently in four-wheel drive mode, others have the option of selecting two or four-wheel drive according to the terrain. For fuel economy reasons alone it is preferable to select two-wheel drive for everyday road driving if possible, unless weather conditions dictate otherwise. Check if the vehicle has free wheeling hubs, and thoroughly understand the procedure for engaging, if applicable and selecting low ratio transmission.
DRIVING STEEP HILLS
Steep inclines are the most common off-road hazard and are potentially the most dangerous. Always travel in a straight line up or down a steep hill and check in advance to ensure that there is a clear exit at the top. When tackling an uphill section, select second gear, low ratio, and use a short run up to gain a little momentum. Try to gauge it so that you crest the hill at walking pace, no faster. This is the speed you should adopt for general off-roading in the interests of the vehicle, comfort and safety. Never try to change gear or direction once committed to a hill, and be prepared for the loss of vision as the sky fills the windscreen on a steep climb – it’s the reason you checked the hill beforehand. If you lose forward momentum, hold the vehicle on the brakes, quickly select reverse gear and let the engine braking control the descent while you look over your left shoulder holding the wheel with one hand to avoid over-steering. Do not use the accelerator.
Driving a steep downhill section needs first gear, low ratio. Once again, check the terrain in advance; making sure the hill isn’t so steep that the front of the vehicle will bury itself in the ground at the bottom. Take your feet off the pedals and let the engine braking take you down the hill at a constant speed, keeping in a straight line. Try to avoid travelling along a side slope. If you have to, keep as low down the slope as possible and be prepared to carefully turn downhill at the first hint of a problem, if in doubt don’t do it.
TACKLING DITCHES AND MOUNDS
Approach ditches or mounds at an angle to allow each wheel to tackle the obstacle individually, making the best use of the available ground clearance. Note that if the obstacle is too severe, it can cause the vehicle to become cross-axled, with the diagonally opposite wheels coming clear off the ground, resulting in no drive, the necessity of a tow or a long walk home. This is one occasion where the axle differential locks come into their own; as they put power to the two wheels that still have traction.
TRAVERSING MUD AND RUTS
Ruts deeper than the clearance under the vehicles axles will quickly have you stuck, so try to straddle them. If the ruts are shallow it is as easy to follow them. Avoid the temptation to fight the steering wheel and always keep your thumbs clear to avoid injury if the wheel spins suddenly. Deep mud is one of the few conditions when a little speed is called for. Build up speed gently before entering the mud and be prepared for sudden deceleration on contact. Stay in gear and take as straight a line as possible to firmer ground. Always attempt to gauge the depth of the mud and be prepared for the worst. If in doubt, reverse before it’s too late. If on exiting the mud, the tyres are clogged drive gently to clean the tread and restore traction.
4×4 vehicles can frequently tackle water several feet deep, but always try to judge the firmness of the underlying surface before crossing. Water should never be driven through fast. A steady speed that creates a gentle bow wave is the correct method, in order to minimise drag and avoid flooding the engine. Always remember to drive a short distance with the footbrake lightly pressed on leaving the water in order to restore braking efficiency.
TYRE PRESSURES – OFF ROAD
In most conditions the vehicle can be driven off-road at the same recommended tyre pressures as on tarmac. However in really muddy, low-traction conditions it can be beneficial to lower pressures slightly to achieve better grip. It is vital that extreme caution is used in these circumstances, as it is possible the tyre can demount the rim if pressures are too low. Always re-inflate the tyres to the correct pressure immediately on returning to tarmac. Serious injury may result from under inflation.
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