Off Road Vehicle Modifications

This Article is in response to the questions continually asked every week of every year, by individuals new to off road vehicles, looking to exploit there true potential in a range of operating conditions. This article is in no way definitive, but looks at the most popular modifications and their most popular uses; it is subjective to a large degree as different people require different things from their vehicle, have different capabilities in working on vehicles, and differing budgets to spend. This article is aimed mainly at beginners looking to acquire suitable knowledge on the proven routes to follow when modifying vehicles.

How do I modify my vehicle? Well, how long is a piece of string would be my usual response.

Before any modifications can take place we have to look at the vehicle, is it in generally good condition, roadworthy, and worthy of modification as many substantial modifications can cost many times the value of a vehicle without adding any substantial value to the finished vehicle. Most of us have seen the pimped up off road vehicles covered in bling or glitzy accessories, fitted with the most outrageously large wheels with the smallest profile tyres which will fit, and nothing among these modifications will improve it’s off road performance. Quite the contrary, many of these modified vehicles will get stuck on an ordinary wet road, or certainly slip and slide around, this article simply contains proven advice on off road modifications, the bling and glitz merchants can go elsewhere.

The first questions should be:

What is my vehicle used for!!! It could be the family vehicle used for everyday duties, to carry the wife and children, and tow the family caravan on family holidays; do the school run and the weekly shopping with husband and wife as the drivers. It could simply be a hobby vehicle which can be used as the basis for a project, and it does not matter if it is off the road for long periods for modifications. We clearly see the need to ask this question as it dictates our modification route.

What do I hope to achieve!!! It could be that I want to improve its off road performance capabilities for mild off road excursions while retaining its everyday use as the main family vehicle, or I want it as a pure off roader and the modifications verge on the ultimate.

How much have I got to spend!!! This is the significant factor in modifying vehicles for off road work, if anyone has huge reserves of disposable income then go and buy a Mercedes Unimog or Pinzgauer and save yourself the hassle of modifications. Everyday realities mean most cannot afford to do this and want to undertake such modifications most will have limited amounts of spare cash and will have to phase the works out over long periods as spare cash becomes available.

When we have the answer to these questions we can formulate a plan, this is probably the most important part of the whole process as it gives a clearly defined objective, and a way to attain that objective; it also gives us the capability to structure a financial plan. This is not as daunting as it may first sound, if your objective is to improve off road traction it may simply mean a new set of tyres, so in reality you can look around for the best tyres to suit your application and obtain the best price on them. To a large degree you are really exploiting or unlocking the vehicles true potential by removing some of the constraints imposed upon them by manufacturers who tailor a vehicle to the “majority” or average user.

Compromise is a word you will often hear, it must be remembered that all vehicles and vehicle modifications are a compromise, a gain in one area will inevitable mean a loss elsewhere, so always consider this before any modifications. Building a hardcore off roader, which is virtually unstoppable off road will mean considerably poorer on road capabilities, poorer handling, braking, etc; so this compromise has to consider the vehicles combined usage.

Let’s modify.


Tyres are one of the most cost efficient ways on modifying an off road vehicle, all road vehicles come from the factory with all terrain tyres (AT), these are always heavily road biased as most users never venture off road in their 4X4, this reflects the best compromise. Tyres are classified in their off road ability as a ratio, this is used by manufacturers when selecting tyres for predominantly road going vehicles, this may be expressed as 90/10 or 80/20; the first number is the on road usage, the second the off road usage. Looking at our first figure we see it is 90, this means it is designed for 90% of its time spent on the road, the last figure is 10, this means it is designed for 10% of its time off road; this gives a tyre designed mainly for road use, but with a little off road capability.

Moving from the factory fit 90/10 or 80/20 to a more suitable tyre for your operating requirements will considerably aid your vehicles traction, this is where you need to be very careful in tyre selection as the more off road orientated the tyre, the worse it performs on road. In reality this means poorer cornering and increased braking distances, as well as increased wear rates as these tyres have less area in contact with the road surface due to their more open tread designs. My suggestion would be to move to a 70/30 tyre for a novice looking for more off road work such as green laning, this does not compromise road abilities significantly, but improves off road capabilities by a significant degree.

Many vehicles now come with overly large alloy wheels, these may look good, but they are fitted with low profile tyres, this means the sidewall height is much lower than an ordinary or higher profile tyre, this is a negative for off road work. Forget low profile, they may be a cheap way of improving on road handling but are detrimental when it comes to off road work, and the easiest way of damaging the often expensive alloy wheels. Low profile tyres have much less sidewall flex than a higher profile tyre, a good off road tyre needs sidewall flex to allow it to move to maintain contact with an uneven surface, and to have its pressures reduced to aid traction in a number of circumstances.
Expert opinion is to never go for a tyre with a profile rating of less than 70 for off road work, 75 or 85 series are best, this means the 355x40x20 tyres are really a no no for off roading.

Many vehicles with the fancy, overly large wheels and low profile tyres often have a variety of wheel sizes fitted to them by the manufacturer; it often means that to maintain the circumference of the tyre, but increase tyre the profile, a smaller diameter wheel has to be fitted. I will explain, I own a Mitsubishi Shogun this came shod with the 20” alloys with very low profile tyres, Mitsubishi fit a variety of wheels and tyre profiles, these range from the basic 16” rim shod with a 75 profile tyre, right up to my 20” alloys with a very low profile tyre. My 20”rims look great, but I want to increase the profile (sidewall height) by the greatest amount possible, I purchased a set of cheap steel 16” rims and fitted the highest 75 profile manufacturer fitted off road tyres, this increased the sidewall height for better off road use.
This ensured the manufacturer fitted wheel and tyre sizes were maintained, but benefited my off road capabilities; it ensured my speedometer remained accurate, beneficial with all the speed cameras, and the cost of five off road rims and tyres was less than one replacement alloy. Mitsubishi charges £549+VAT for a replacement alloy rim, minus its tyre; my cheap steel rims were £32 each (£160) and the Cooper 20/80’s off road tyres were £87 each (£435); the total cost of steel rims and tyres are £595 as opposed to £631.35 for a replacement alloy.

Tyres come with a variety of names and anachronism’s which can confuse many people, these will be explained.

R/T - Road terrain, this usually means it is a radial tyre as fitted to an ordinary motor car.

A/T - All terrain, this is an all terrain tyre suitable for many uses, check its usage ratio to find its degree of road, and off road usage. A/T’s are the most commonly fitted tyre for off road use as they are a good all round performer.

M/T - Mud terrain, these operate best in muddy conditions.

M&S - Mud and slush, these are something of a misnomer as any predominantly road biased tyre outperforms these in muddy and slushy conditions, some manufacturers prefer this term as it is a useful term to confuse an uneducated public.

Specialised tyres – these are tyres designed for a specific use, these may be the excessively knobbly tyres designed for one specific purpose such as ultimate competition use in deep mud, or rock climbing, and are generally of little use outside their specific use.

Many myths and misconceptions are rife among the less educated on tyres, this often leads to the incorrect advice from many amateurs, this can be costly to newcomers entering the world of off roading, again, we need to look at our vehicle usage. If our main vehicle usage is as the main family vehicle which will venture off road occasionally for a little green laning we need to stick to the 90/10 or 80/20 tyres, these operate better at higher road speeds and give a good tyre life. Grip levels are significantly better, handling and braking are better, and their winter use on ice and snow are the best of all the classifications, this is often disputed, but testing and operational use has proven these to be the best. Moving to a 60/40 or 50/50 for general road use with occasional off road use means worse handling on road as unlike our 90/10’s, these more open, aggressive tread patterns actually dig through the surface. Their design means they are designed to dig through the slippery surface layer to find a more solid sub layer, they grip onto this more solid sub layer to provide traction and give forwards movement, they tend to be softer compounds which decrease tyre life on solid surfaces such as roads and rocky surfaces.

Moving onto the really aggressive A/T’s such as the 20/80’s and M/T pattern tyres, these really dig through the surface which explains their use, they operate best in heavily mudded areas, but have a very short road life, they do what they do, well.

Many novices will now have an idea of tyre types and selections, but this raises another often asked question, and quandaries; what can I do as my vehicle comes with large alloys and very low profile tyres.
The answer is simple, decide what tyres you need for normal everyday vehicle operations and fit them to your alloys, and purchase a cheap set of aftermarket steel rims and fit tyres to suit “your” off roading conditions. These, save your expensive alloys and allows your road tyres to offer the best performance and tyre life, swapping to your cheap aftermarket steel rims and chosen off road tyres works out safer and cheaper.

Optimum wheel sizes are currently 15”, these have the greatest availability of tyre types and styles available, this means the greatest choices for off roading, and the most competitive pricing, this, is followed by 16” rims which are becoming popular.

Recovery Equipment:

Recovery equipment becomes essential for anyone venturing off road, the amount of recovery equipment varies with the conditions you intend to operate in, most basic equipment can be found around the home, but some will have to be purchased.

Shovels are the most basic, even the most extensively modified vehicles become stuck, a basic shovel will allow you to dig out a vehicle, even if it takes several hours to do so, my preferred type is the military folding type as it is a combined pick and shovel. These are readily available, and come in a variety of styles and qualities, as with most equipment, buy the best quality you can afford.

Tow ropes are essential, forget the garage types which are cheap and nasty, these are designed purely for the occasional recovery of road vehicles, on the road; a bogged off road vehicle will often need in excess of three of four tons of constant pull to free it. Many types of towing equipment is available, specific recovery ropes for off roading are available in a variety of lengths and capacities, as a minimum aim for a capacity of 8 tonnes minimum with a length of 8 metres or longer, these are cheap to purchase.

Towing straps are also available, these are similar to the often seen ratchet straps in appearance, but unlike ratchet straps, are specifically designed for vehicle towing and recovery, again aim for 8 tonnes minimum, and a minimum length of 8 metres.

Kinetic recovery straps are similar in appearance to ratchet straps, they operate in a different way to the towing straps; they operate much like an elastic band as they are connected between the two vehicles, but not tightened. Being left loose means the first vehicle drives off, this tightens and stretches the kinetic strap, the first vehicle stops and the strap contracts, pulling out the stranded vehicle. Kinetic straps have built in wear indicators, and limitations to the amount of operations they can perform, they then have to be left for 24 hours to normalise themselves before they can be used again.

Anyone looking at this type of equipment should always buy two of each, they can be connected together to double the operational length, or doubled up to give a higher puling capacity without, or minimising breakage or damage.

Saws/Axes are often very beneficial; a good all round wood saw has saved many off roaders when trails become blocked by falling tree branches, or to allow a stranded vehicle to be recovered by cutting up fallen branches to pack under wheels. Axes allow timber to be easily split to use as packers under the wheels of bogged vehicles, the flat rear face also doubles up as a hammer.

Pruning equipment is beneficial during the summer months, a decent set of pruning shears will allow the years growth to be trimmed where it impedes a lesser used track.

Hydraulic jacks, plywood squares and plywood strips are often better then the standard vehicle jack, buy a 6 tonne model or higher, the plywood squares should be in a variety if sizes, these are placed onto soft ground to stand the jack on. These squares prevent the jack from sinking into the soft ground; strips are to pack the base squares on uneven ground to provide a flat, stable surface to jack from. Lift is essential; the capacity is worthless if the jack does not lift a vehicle high enough to allow packing to be placed under a slipping vehicle, this can be compensated for by carrying more plywood packers of squares to add to your firm base to raise the height.

Hand pulling winches, these are available cheaply in a variety of styles and capacities, go for the slightly more expensive types designed for off road vehicular use, these operate at higher capacities then the often marginal 2 tonne cheaper units. These will pull a vehicle out, but will require considerable operator input as well as a range of accessories to allow then to be used to extract a stuck vehicle.
Tree strops are an essential for any winches, these wrap around a suitable object such as a tree to allow the winch to connect to it without damage, the towing straps can be used as extensions, a variety of appropriately rated bow shackles or “D” links will also be required.

One word of warning, do not use the manufacturer fitted recovery points, or the manufacturer supplied screw in type towing eyes for recovery work, they are simply not strong enough and will often tear out when under heavy loads. Proprietary aftermarket items are available; these should be correctly mounted, and are designed to take the high loads imposed upon them, the original items are designed mainly for lashing the vehicle during transportation only. Many people have failed to heed this advice and become severely injured during recovery operations where these manufacturer lashing eyes have torn loose and hit them.

Tool boxes are necessary to store and house this equipment, which should be considered a minimum unless you’re off road routes are confined to solidly surfaced routes which are well known to you. If you have a restraint system or tie down hooks in your vehicle, use them; ensure your tool box has external fixtures to allow them to be fastened down in your vehicle, do not put loose tools in the vehicle as they can do considerable damage to your vehicle, or you.

It is assumed that you will carry a basic set of vehicle spares as well as a basic toolkit to perform basic trail repairs.

Vehicle Protection:

Many off road vehicles come with some form of off road protection; many others do not offer any form of vehicle protection, most which do offer protection manufacture it from the thinnest, cheapest plate they can fit, for real off road work, is useless. Upgrading it to a more suitable type is beneficial when off road work of most types is undertaken; the sole purpose of underbody protection is to protect the vital components of the vehicle such as the engine sump and gearbox/transfer case. Enclosing these components also protects other vital vehicle components such as the throttle/clutch cables, brake pipes, rear heating pipes, and air conditioning equipment, these are all more expensive to replace than the correct underbody protection. Two options exist for underbody protection, buy a basic kit and add to it as your off road experience grows, or; if you have the capabilities and equipment, manufacture your own bespoke items to suit your purposes.

Basic kits will cover the engine compartment underside and the gearbox/transfer case assembly, this must be considered a minimum requirement, and must have no protruding items such as mounting bolts on or below the lower face. Additional protection such as axle protectors, suspension protection can be added at a later date.

When looking for underbody protection it is prudent to know what to look for, the plates must be a minimum 4mm thickness for steel and 6mm for aluminium; obviously, thicker offers better protection but weight must be considered and balanced against the vehicles use. Other things to look for are airflow, the engine needs a reasonable amount of airflow to cool the lower parts of the engine and gearbox, these rely upon this air to cool them, another important aspect is the exhaust, this needs plenty of airflow to cool it. Cleaning is another important consideration, many using there vehicles in muddy or heavily grassy conditions will find this builds up over time, mud obviously clogs everything up and causes rust, dry grass in contact with the exhaust can ignite with obvious consequences. Reinforcing members on large expanses of flat plate are necessary to stop it deforming during contact with the ground, and ease of removal is an important consideration for vehicle maintenance.


Many ask why lighting is so far down the list, well; most of this is for the image conscious, the big names exploit this into sales of their often considerably expensive products. Let’s ask what good lighting a route up two miles in front is when you have road tyres fitted, and you are stuck in deep mud, or your sump has been ripped out and the engine is seized because you have no underbody protection, this puts it into context. Very few people off road at night, many may be there after dark because they have become stuck, or misjudged the time taken to drive a route because they may have had to clear a blockage from a fallen tree, so the majority of aftermarket lighting is pure vanity.

Before we look at lighting we need to know what types are available, and how they work in an off road situation; most lighting can be defined as two basic types, these are spotlights and fog lights, we now need to understand the differences.
Spotlights are as their name suggests, spots of light designed to have a very narrow beam of light focused over a very large distance, fog lights are a totally different, they, throw out a very wide angle of light over a very short distance.
Both sorts are best fitted to an off road vehicle, one pair of each means a concentration of light directly in front, and to the sides of the vehicle from the fog lights, and long range from the spotlights, so we use both.

Most off road driving involves considerably more reversing than normal road driving, the reversing lights on most vehicles are very poor in terms of light output in most conditions, and offer no visibility when reversing off road, with its many obstacles. I prefer to upgrade the reversing light by wiring in a fog light, this gives considerably more light over a short distance, but illuminates a very wide angle either side of the vehicle, wide angles are very beneficial where there are trees or ditches. This is always my first upgrade to any vehicles lighting system, the next is the handheld light, the type which fits into the cigarette lighter, these have the advantage of being aimed wherever anyone wants, and are more flexible than fixed lights.
I prefer not to use the cigarette lighter socket with these, they make a poor contact and heat up the plug and socket rather quickly, many are fitted with an inbuilt fusible link, this often blows and means the cigarette lighter becomes inoperable. I cut the plug off the light and buy bulkhead mounting sockets, I mount one in the dashboard, one in the rear of the vehicle, and one under the bonnet, and one plug which is fitted to the light, these sockets come with waterproof covers. Using these sockets mean once plugged in, the light plug is locked into the socket, this gives a much better electrical connection with no heating or temperamental flickering light, these types of sockets can be upgraded to any power output requirement.

Using these types of handheld lights and modified sockets means the lamp can be used anywhere around the vehicle, including underneath it if you become stuck, or even have a flat tyre, the additional light is much safer to work under. These are a much better option for the novice or beginner, and make them less vulnerable when working underneath a vehicle when cleaning debris, or jacking up the vehicle.

Many newer vehicles come with fog lights fitted as standard, if your vehicle has them, great; if not you will need to fit a set, I prioritise these over spot lights as these are again, the most flexible when used in conjunction with the vehicles headlights. Finally I fit spotlights, these are usually mounted in front of the radiator, the roof bars may look nice with lights on, but are impractical when entering low level car parks, and are often subject to off road damage from low level tree limbs or bushy growth.

Fixed work lights are another option, these are purely subjective and it depends upon your vehicles usage as to whether you decide to fit them or not, my opinions are than the hand held lights are a lot cheaper and more flexible, I actually have two hand held lights.

Finally; before venturing off road, know your vehicle; ensure you know where your jack and wheel brace are, and if they are even with the vehicle, and there the jacking points are located, study the handbook so you know your vehicles clearance or wading depth.

This concludes the basic modifications for anyone wanting to modify their vehicle for off road use, much of it is a little knowledge and gaining experience; always remember one golden rule, protect your vehicle at all times.

Off Road Modifications – Intermediate