A tyre suited to sand or normal road use clogs rapidly and quickly loses traction in mud. The large gaps and open, chunky tread of mud
tyres facilitates ‘self-cleaning’. Ideally, as the wheels rotate, any mud embedded in the tread is thrown out. Heavy treads tend to make more noise than fine treads and this is most noticeable on tar at medium speeds. Purpose built mud tyres do not have good wet road performance, so extra care is needed in these conditions.
Mud tyres can work well in sand as the deep tread seems to aid traction here too. Also, many mud-terrain tyres, such as BF Goodrich Mud Terrains have a particularly flexible sidewall, and therefore give better than average mileage and performance when used for extended periods running at low pressures.
Generally speaking, mud tyres with reduced pressures work in compacted snow conditions. Virgin, powder snow requires huge balloon tyres, that would also be good in sand, at very low pressures.
The main feature of a tyre designed for sand is not, as is commonly thought, broad width, but a tread pattern that compresses the sand beneath the tyre instead of penetrating through it – which is what happens when a mud tyre is used on sand. The gaps in the sand tyre tread are narrow and the tread pattern runs longitudinally around the tyre. Good sand tyres flex well when used at low pressures. Sand tyres must also be tough enough to withstand rough tracks and sharp stones of semi-desert regions, since rarely do pure sand conditions last for long before being interrupted by sections of sharp stones and gravel.
Tour operators in the Namib have chosen a BF Goodrich Mud tyre as their first choice. This is a surprise to me, but they explained that traction with this or any other tyre does not seem to make a significant difference in the conditions, but this tyre has the ability, unlike most, to survive long distances running at very low pressures. The sidewalls of other tyres, they tell me, tend to break apart
Not all vehicles are designed for very broad tyres. On some vehicles the tyres may rub the steering arms, brake hoses or the chassis when the steering is on full lock. If your vehicle is blessed with good axle articulation, oversized tyres may rub against the body when the axles are extended during off-road travel. They also put undue stress on transmissions not designed for the use of big tyres.
Broad tyres in sand
It’s a mistake to think that very wide tyres will automatically be suitable for sand operations. That’s due to the belief that it is the tyre’s width that affects its penetration. Although this is to a small degree true, almost all of the advantage gained by a tyre’s width is counteracted by the fact that broad tyres have a much higher rolling resistance than do narrow tyres. This is due to the tendency of a tyre moving over sand to build up a wall of sand in front of it. The wider the tyre tread, the higher the wall. Eventually the vehicle’s progress is halted as the wall becomes higher and higher and the drag overcomes the engine power or traction. Narrow tyres create narrow sand walls, and so have lower rolling resistance.
Broad tyres in mud
I have witnessed occasions when broad tyres have had a distinct disadvantage in mud; and other times (albeit less frequently) when they have been an advantage.
One dry winter on Vaal Dam I was asked to assist a Ford F250 fitted with Yokohama Super Diggers, a common broad tyre better suited to sand. The craft which the Ford was attempting to pull out was a lightweight ski boat with a 30hp outboard. Once the tyre treads had clogged the vehicle became useless. My vehicle was fitted with 205X16 radial mud and snow Michelins at 2,3-bar. Not only did I extricate his vehicle and boat in tandem, but then proceeded to pull a five-ton yacht up the same slip way.
In comparison, consider the case of three Land Rover Defenders fitted with 750X16 Michelin XL mud tyres inflated to 2.5-bar trying to mount a steep muddy slope during a hill-climb. While the Defenders struggled to get up the hill, the Isuzu KB diesel I was driving walked up without so much as the slightest wheel-spin. The Isuzu was fitted with Continental RVT280s, 265/70R15, a broad general-purpose off-road tyre, also inflated to 2.5-bar.
Then there is a case of the Darien Breakthrough expedition where two Range Rovers travelled from Alaska to Cape Horn in 1972. The wide tyres caused major transmission failures in the thick jungle conditions of Central America. When the tyres were swapped for much narrower ones, speed increased and breakdowns stopped.
There seems to be no definite conclusion when is comes to mud tyres and tyre width. What is conclusive though, is that a self-cleaning tyre does make a significant difference to performance in mud.
Don’t mistake a heavy knobby tread for toughness. The thickness of the sidewalls is of as much importance as the thickness of the tread. Tyres of this type have restrictive speed ratings when they become specialised very-heavy-duty types. If your vehicle is operating under constant off-road conditions where resistance to damage is more important than traction, cross-ply tyres may be worth considering.
All purpose 4×4 tyres
The vast majority of leisure off-roaders will require a tyre to handle all theatres of operation: sand on the beach or on safari, mud for the occasional rainy spell that turns the tracks into a slippery mess, and rocks on the family weekend 4×4 outing. No single tyre stands out as being the best for all conditions. The best way to choose a tyre suitable for your needs it to talk to experienced enthusiasts who have been there before, because you can’t tell by just how they look.
How important is side-wall thickness?
Sidewall thickness is important in preventing tyre damage, no doubt about it, but very few radials are made with more than two plies in the sidewall. A few, such as BF Goodrich ATs and MTs, have three plies, but these tyres, as good as they are, don’t necessarily get fewer sidewall punctures than others with two. Why is this? I believe that it has as much to do with the thickness of the sidewall as it does with its shape.
Sidewalls that have a block shape, as opposed to rounded, tend to protect themselves better as the shape deflects obstacles when the tyre rides over them. A rounded crown will permit sharp objects to penetrate or damage the sidewall even from underneath.
I do know that the fact that I now have three plies on my BF Goodrich AT’s sidewalls, gives me more confidence than if I had two.
• Heavy tread far apart: good for mud, mediocre in sand.
• Medium tread close together: good in sand, mediocre in mud.
• Thick tread: good for sharp rocks, often combined with hard compound rubber which will wear well on rough tracks. Will not flex well – a disadvantage in sand.
• Thick sidewall: good for sharp rocks. Good load rating. Less ability to flex in sand. More resistant to damage when at lower pressures due to the strength of sidewall.
• Not all tyres are alike when it comes to staying on the rim when deflated. Ask around as to which models work best.
Speed load and temperature
The maximum permissible speed is printed on the tyre sidewall. Tyre damage will result if this is exceeded. When a tyre is deflated for reduced penetration, the permissible speed rating no longer applies and is significantly reduced.
The maximum permissible load is printed on the tyre sidewall. Tyre damage will result if this is exceeded, particularly if high speeds are attained.
Heat blowouts can occur to inner tubes before the tyre is affected. The result is an inner tube that shreds itself and after such a blow-out it is irreparable. Heat damage to tubed tyres is less frequent but will result in sidewall over-flex and delamination. Again such a tyre is irreparable.
Magnesium alloy rims
Some mag rims are weak and unsuitable for heavy off-road operations, for example the standard mags supplied with the Mercedes-G 463-series. But many are quite strong enough for most uses. Their disadvantage comes when they are bent, when they are much more difficult to repair and a hammer and a tree stump isn’t going to bend them straight: It will just break them more. Steel is the better, but heavier and uglier choice for those wanting uncompromised strength and durability, but in 90 percent of users, it will make little difference one way or the other.
Steel rims are constructed in two parts: A pressed steel center
boss and a rolled circular bed for the tire. These parts are either riveted or welded together, riveted types being the strongest and most reliable. Steel rims are sometimes of inferior quality and in some cases severely warped rims are supplied with new vehicles, making perfect balancing impossible.
Damage and repair of steel wheel rims
Common causes of damage are overloading, running with less than the full number of wheel nuts (See pictures below) or driving over rocks, etc. Make sure that wheel studs are clean and lightly oiled otherwise stud nuts can tighten against dirt and rust. Running with loose wheel nuts can cause severe rim distortion which is irreparable.
Slight damage can be easy to repair, e.g. bending of the outer flange. This can be straightened using a shifting spanner and light use of a hammer. Make sure the flange is returned to its original shape and the distortion has not been transferred along the flange. Because wheel rims are made from high grade steel, welding should not be undertaken owing to the possibility of the temper being altered by the heat and resultant weakening of the rim.
Maintenance of wheel rims
Rust is a bit of a maintenance headache when it comes to wheel rims. Because of the habits of male dogs and the fitting of tires when the rim flange is unclean, tires can weld themselves to the rim making them very difficult to remove. It is a good idea to remove each tire from its rim and then to refit them before going on an extended safari to avoid having to repair a puncture in the bush and spending three hours simply trying to remove a tyre from a rusted rim. One solution is hot-dip galvanizing but beware of deposits on the tire flange requiring smoothing down. Red-oxide paint or sand blasting and powder coating are possible alternatives.
Some older vehicles were fitted with split rims of a two part design. This facilitates the removal of the tyre from the rim. It is imperative that the tire be totally deflated prior to splitting the rim as air pressure remaining in the tire will cause the rim to split with explosive force which could cause serious injury. To prevent tube damage, when a tube is fitted onto a split rim, a protective gaiter consisting of a ring of shaped rubber must be inserted between the rim and the tube.
Tyre design has come such a long way since I first went off-roading and I have come to the conclusion that tubes tyres, for all but highly specialist applications (don’t ask me what these might be) tubeless is the only way to go. As a general rule, tubeless tyres are: as tough, easier to repair (in most situations), are far safer, give better grip, better braking, use less fuel and suffer far (FAR!!!) fewer punctures and are altogether the better choice for overlanding.
Up until ten months ago (mid 2010) if someone had to ask me, what is the best tyre for overlanding use, I could not give a definitive reply. This is no longer the case. During my TV shoot for Take A Deep Breath, season-2, I travelled ±27 000 kms through Namibia, Angola and Botswana. Before this, I had done a trip through Mozambique and crossed the Kalahari. I did all this on a single set of tyres and did not suffer a single puncture or had a single issue with my tyres. I have never known such fantastic service from a set of tyres. The tyres were BF Goodrich, ATs, 265/75R16 on a Toyota Land Cruiser 105 wagon.
The question of tubed or tubeless is much debated.
Tubes versus Tubeless
• A tubed tyre running at reduced pressures for long periods generates more heat and is more prone to damage and punctures.
• A tubed tyre is easier to repair in the bush than a tubeless, when on a split rim or rim with narrow flange because they are easier to remove from the rim. However, tubeless tyres can often be repaired with a simple plug, not usable with tubes.
• Tubes do not strengthen the tyre or help prevent punctures, if anything, the reverse is true.
• If a tubeless tyre is deflated for use in heavy sand conditions that require excessive throttle, the tyre may move on the rim. The result is total deflation.
• Blowouts occur less often to tubeless tyres. In tubed tyres, sudden deflation can be caused by excessive heat that is aggravated by friction between the tyre casing and the tube. This is especially serious if the tyre is under-inflated or overloaded where tyre distortion increases this friction tenfold.
• Damage to tyres is common in outback travel. If you use tubeless tyres, carry a suitable tube to enable you to effect a repair should the damage be sufficient to render the tyre useless for tubeless operation. It is very unlikely that you will find the tube of the correct size when you need it and even if you do not intend to go into very remote areas, carry a spare tube.
• Blowouts can tear a tube to pieces rendering it useless, so if you use tubed tyres, carry several spare tubes.
Fitting inner tubes
When fitting tyres with inner tubes it is imperative that once the tyre is inflated it should immediately be deflated and then re-inflated. This will remove twists in the tube. If a twist remains, the tube may split. Evidence of tube failure of this nature can be detected as the tear begins at the point of highest stress, normally the valve. Many tyre fitting workshops do not know this, so you should keep and eye on the fitting operation and make sure that this operation is carried out correctly.
Radials are superior to cross-plies in almost every respect except price. They offer superior traction, safety and comfort, both on a paved surface and off-road.
Radial tires are made by laying strips from flange to flange (the flange is the point where the tire meets the rim). The advantage of this design is that flexing of the sidewall does not affect the tread. They flex independently of each other. So, decreasing pressures will flex the sidewall and tread area, while keeping the tread pressure evenly spread and increasing the tire contact area with the ground, thereby decreasing the ground pressure and the tyre penetration.
These are constructed by laying strips of fabric over each other at 90° angles, forming a wafer effect. These strips are called plies and the more plies a tire has the higher its load carrying ability will be, while its flexibility is reduced. They were first used in the 1860s and apart from improvements in the materials used they have changed little in design. When the side wall of a cross-ply expands with deflation, the ground pressure in the middle of the tread decreases. At the same time the ground pressure on the outside of the tire increases. The lower the inflation pressure the more marked the effect.
When the tread bar of a cross-ply meets the ground it bends. This causes the weaker area of casing behind to distort, allowing the tread bar to move backwards. As the tire rotates and the tread leaves the ground, it flicks back to its original position. This movement, combined with the distortion of the tread described above, causes trauma to the surface over which the tire is passing. In sandy conditions, this trauma, exaggerated if the cross-ply is under-inflated, will cause the tire to dig in. Cross-plies are therefore unsuited to heavy sand conditions.
Cross-plies also have a higher rolling resistance than radials and this will affect fuel consumption. Perhaps the only time that cross-ply tires could be advantageous is when the vehicle spends most of its time carrying heavy loads at low speeds over hard rocky ground that could cause damage to more expensive radials.
The location of spare wheels carried by 4×4 vehicles varies, and each position has its advantages and disadvantages.
Inside the vehicle
A spare wheel carried inside the vehicle means that you may have to unpack your luggage to get to it. It takes up valuable load space that could be used for more delicate articles. Because it is heavy, it is important that it is well secured.
Under the rear overhang
A spare wheel hanging behind the rear wheels in many cases reduces ground clearance, sometimes seriously (e.g. Toyota Land Cruiser SW). In this position, it is vulnerable to damage, sticks can puncture it, and should the vehicle bog down, the spare wheel can make things worse. A spare wheel makes an excellent base for a jack and even a good anchor if it is buried, but can become inaccessible when mounted here. In addition, if it is stolen or falls off, it is unlikely that anyone will notice until it’s too late.
On a roof-rack
While only light bulky objects should be carried on the roof, a spare wheel carried here is ideal because it is easily accessible, can be secured well forward to aid weight distribution, and the bowl of the wheel rim can be used for sitting in when game viewing and is the ideal location to carry a three-legged pot. Keep in mind the average steel rim and tire will weigh in excess of 35 kgs, so it may take two people to lift it on and off the roof-rack.
On the rear door and purpose-built spare wheel carriers
A spare wheel carried on the rear door is without doubt convenient but negatively affects weight distribution and on some vehicles not originally designed to have it there, has odd effects on handling. Some door mountings are not strong enough to take the constant vibrations in rough country and eventually break. The Land Rover Defender’s rear door is notorious for cracking and so a purpose-built spare wheel carrier must be fitted. If the wheel is attached directly to the door, the hinges and clamps should be periodically tightened and the door jam set so that there is no free play.
Purpose-built wheel carriers are available for a range of vehicles. Being separate from the rear door they can also be a useful place to carry other equipment such as a spade, jack and even a cooking grid.
On the bonnet
Looks really cool on a Defender, but putting a spare on the bonnet isn’t very practical and is only really possible with the Defender. Problems can arise when the bonnet release knob is pulled from inside the vehicle as the bonnet often does not release due to the added weight. It can therefore be difficult for a single person to open the bonnet. Forward vision is also restricted and safety in a head-on collision is seriously compromised. Removing the wheel and replacing it requires some physical strength and will scratch the bonnet’s paintwork. The only advantage of this position I can think of is that it offers excellent weight distribution.
12-volt electric tyre pumps
Electric pumps available vary greatly: Some are quick, efficient and costly and others are simple devices more efficient at converting noise into heat than inflating a tire.
When selecting a pump, the volume of air pumped is the issue, not the pressure. Look for a high cfm (cubic feet per minute) or lpm (liters per minute). Most imported pumps indicate cfm. Anything under 1 cfm is going to be slow. Anything over 1,3 is going to be reasonable. Not many perform better than 2 cfm. The pressure rating is not important as long as the pump can reach 4-bar. Note: The volume of air must be measured under pressure. Some pump’s specifications look outstanding until they are applied to a half-pumped tire and then they fall off dramatically.
Electric pumps are fairly reliable, but if they break down they are not easy to repair. It’s therefore advisable to carry a foot pump as a backup. Foot pumps are perhaps a little less strenuous to use than hand pumps, but their use in sand can be awkward. They should be placed on a plate or tarpaulin to keep sand from entering the mechanism.
Solutions to the dilemma of letting tyres down quickly have plagued mankind for oh, at least 25 years. Tools range from the long fingernail, a twig or matchstick, the tip of a Leatherman or penknife and recently auto deflators like the Staun, which is the best of them. Screw them onto the valve of each tire and they deflate each to a preset pressure. But I have found something I like even more: The ARB EZ-deflator. It is very fast, very convenient and safe: there is no guesswork that each tire is at the desired pressure (pictured left).
The most accurate and reliable pressure gauges are not digital. The best ones are the more expensive analogue gauges that have a clear gauge measuring in a wide arc, pressures up to but not exceeding 4-bar. The reason for this is that gauges designed for trucks will measure accurately at high pressures, but inaccurately at low pressures. Off-roaders need accuracy between 0.2 bar and 3 bar.
Repairing a puncture
Tyre maintenance tool kit:
• Electric tire pump
• Foot tire pump
• Tubeless repair kit/Tube repair kit combination
• 2x tire levers
• 2nd spare wheel
• Spare inner-tubes
• Jacks and tools to remove and replace wheels
• Spare valves and valve tool
• Pressure gauge
Carry a second spare wheel and tube
By carrying a second spare, a puncture need not be repaired immediately. If the second spare is required, this is the time to make a repair. Do not wait until your vehicle is immobile before you make a repair or you may find your vehicle immobilized in a position which makes it difficult for you to work. Change to the spare, drive to a shady place or set up camp and then repair the puncture in a relaxed, unhurried fashion. It may even prove enjoyable and will feel like part of the bushwhacking experience.
These instructions are for repairing punctures while the tyre remains on the rim. As these plug repair systems differ slightly, read the instructions that came with your kit.
Locate the item causing the puncture and draw a circle around it. Do not assume that if you find what seems to be a nail/thorn in your Tyre that this is the only cause of the puncture. Look carefully at the entire tyre including the inner and outer sidewalls marking all irregularities. Remove the nail/thorn. Insert the plug into the spiker and apply cement (some systems do not require cement) to the plug. Insert the reamer into the hole and move it in and out a few times to roughen the edges so the adhesive will stick. Insert the plug and withdraw the spiker according to kit instructions. Inflate the tire and splash water over the repair and over any other suspect areas checking for bubbles.
These instructions are for punctures that cannot be repaired with the tyre on the rim, making allowances for the fact that the tire patch (tube patches do not work on tires) will be cemented (solution for tubes may not work on tires and tire patches) onto the inside of the tire. Read the literature that comes with the repair kit and follow the tire removal procedure below.
Inspect the tyre and mark any objects which could have caused the puncture. Do not remove the object at this stage. Place the flat under your vehicle and use the jack and the vehicle’s weight to break the seal between the tire flange and the rim. Breaking the flange (separating the tire from the rim) is the first and often most frustrating task when repairing a puncture in the bush. The problem is that when the tire is driven over, or crushed using a high-lift jack, the opposite side kicks up. To prevent this, two high-lift jacks placed opposite each other and worked together works well. If you only have a single high-lift, use a bottle jack or similar to prevent the wheel from lifting.
Once the seal is broken, place the wheel on a ground sheet (it is important to avoid dust) and remove the valve. With a basin of slightly soapy water at hand, wet the tire levers. Stand on the edge of the tire and insert the levers between the tyre and the rim. Work your way around the tire until the flange is over the rim. NOTE: Not all wheel rims are symmetrical. Start with the outside (the side with the valve). If you have difficulty removing the flange, try the other side of the rim. Then with the wheel standing upright, remove the tube where
you think the puncture has occurred and mark it. Then remove the rest of the tube, replace the valve and inflate it. The puncture should then become easy to find. Immersing the tube and watching for bubbles is another way of locating the puncture, and may also reveal other defects such as a leaking valve. Mark the puncture and deflate the tube completely.
Repair kits come with a scraper which is then used to roughen around the puncture site after the tube has been dried. Clean away any rubber particles and apply the rubber solution. When it is touch-dry, remove the backing and apply the patch. Rub over the patch with the round end of a screwdriver handle or similar object until
you are sure that a good bond has been made. Clean out the inside of the tire and remove the object that caused the puncture. This is a good time to inspect the outside too, and remove any thorns, stones or nails that may be working their way through the tire. Dust the tube with talc and fit it inside the tire with the valve intact. Soap the tire flange and, with the tire levers, work your way towards the valve, pushing the tire over the rim. Be careful not to pinch the tube with the tire levers.
The final stage is to inflate the tire. Roll the wheel looking at both sides checking that the tire is seated uniformly on the rim. Then deflate the tire and re-inflate it. If the tube is not correctly aligned it may split when it is run.
Getting a puncture on a steep slope
I have on two occasions needed to replace a wheel while my vehicle was pointing skyward at about 20°. This is no easy task. Preventing the vehicle from rolling off the jack is the first priority.
These are the steps:
• Wedge all wheels with rocks or chocks.
• Anchor the vehicle using its winch cable or a chain to another vehicle. Do not use stretchable rope or a kinetic strap.
• The winch cable must be fully stretched before jacking can begin.
• Engage low-range first gear and lock all differentials that you can.
• Firmly apply the hand-brake.
• Remove the spare wheel from the vehicle before jacking.
• Have all occupants leave the vehicle before jacking and have them stand to the side. Keep bystanders from walking behind the vehicle.
• Make sure the vehicle remains stable as jacking begins and jack slowly.
• Only remove the rim once you are confident that the vehicle cannot roll further and fall off the jack.
Advice when fitting tyres
I rotate tires every 15 000 kms to even out wear. Balancing should be done every 35 000 kilometers or thereabouts. With heavy 4x4s, only when balancing is radically out is the vibration serious enough to be transferred to the driver. I always oversee the operation when tyre fitters replace or rotate my tires. I make sure this is done properly: All the tires, including the spare, are fitted with metal valve caps to keep out mud and dust. I make sure the wheel nuts are not over-tightened. This is very common. If you are concerned, do the final tightening yourself. The average 4×4 wheel nut should be torqued to approximately: 66 – 74 ft/lbs equivalent to 90 – 100 Nm. The good fitment centers set theirs to 120 Nm, which I think, is too high.