The Truth About 4WD Tyres
Ask five different 4 x 4 experts which is the best tyre and chances are you will get five different answers. Most likely it will be something like “Bridgecooper Sandcrunchers” or “Goodstone Rockwrestlers” or some other heavily advertised, high profile product.
Marketing and machismo plays a huge role in selling four wheel drive tyres just like marketing and guilt play the same role in selling tyres for passenger cars - “...a car skids, white knuckles claw the steering wheel and tyres compress against a wet road. The car stops inches from the terrified child clutching her doll. You have saved this childs life because you purchased Michelyear Lifesaver Tyres.”
Tubeless or Split Rim
(diagram shows conventional tubeless rim versus split rim with locking rim)
Once all vehicles were produced with split rims. Cheap to produce and easy to service no one considered putting anything else on their car. There were no options. The deserts and bush of countries like Africa, Australia and the US were opened up and fully explored on split rims and bias-ply tyres.
In 1985 Toyota released the venerable 75 series Landcruiser, one of the most successful working 4WDs ever released. It came out with grey split rims and 750R16 rubber – tall, skinny tyres sometimes referred to as “razor blades”. Before long every man and his dog had ripped this combination off and fitted 15 inch one piece rims and “Desert Duellers” – big fatties.
Everyone that is except the farmers and station owners and the mining industry and the army. They left the standard tyres and rims on their Landcruisers because they really use them for 4WD. They drive over rocks and sand and through rivers and over trees and on the worst corrugated gravel roads. Some of these vehicles spend their whole lives with four wheel drive engaged. True, part of the reason is the ability to resist and repair punctures. Split rims, with tubes as standard, are much easier to repair than one piece tubeless rims. Huge advantage if you are stuck in the middle of nowhere with 3 flat tyres
Fashion or Function
We're not saying that split rims and razor blades are the best solution for everyone. We're simply suggesting that most 4wd tyres are purchased because of trends and fashion rather than need “…and would you like raised white lettering or plain on those tyres Mr Smith?”
Desert trekkers, pastoralists, geologists, doggers (dingo trappers) and the army run split rims and bias-ply tyres so they can be self reliant in the middle of nowhere. Bias-ply or “rag” tyres have varying multiple plies designed with strength in mind rather than comfort. These plies run around the tyre sidewalls and have a generally heavier construction to resist staking. These people need to be able to avoid or repair 20 punctures a day without access to a tyre shop.
Today there is choice. Most 4WDs on the road today are fitted with tubeless rims and radial tyres and for most people a tubeless steel belted radial mounted on a tubeless rim will be the best compromise for 95 percent of 4WD activities. Steel plies beneath the tread supply good high speed highway strength while allowing the tyre to grip and mould reasonably well off road. Thin flexible sidewalls allow for the dissipation of heat and enable you to decrease tyre pressure and use your tyres as a kind of shock absorber on badly corrugated tracks. They will perform admirably on soft hungry beach sand, picking through rocky creek crossings or slipping around on muddy hills. The rest of this article will deal with this style of tyre.
Highway Terrain, All Terrain, Mud Terrain or perhaps Light Truck?
We spend most of our time driving and a large proportion of that time off road and off track. We travel heavy and cover lots of kilometres and wear out lots of tyres and we swap around between split rims and tubeless, depending on the situation.
Here's a rough guide to tyre types
(H/T) Highway Terrain = 90% Road & 10% Off-Road
(A/T) All Terrain = 60% Road & 40% Off-Road
(M/T) Mud Terrain = 15% Road & 85% Off-Road
Any one of these three types of tyre will perform adequately in most 4 x 4 situations. Let me say that again in a different way. A properly maintained vehicle with correct tyre pressure and a reasonably proficient driver will be able to negotiate nearly all off-road situations. Basically a modern 4WD will go anywhere you can walk. If you are able to walk up a steep, snotty, slippery rock 500 metres upwards then chances are your 4WD can drive up it. And chances are that it won’t matter if your tyre is a Highway Terrain or Mud Terrain.
Having said that, if we never took the 4x4 off-road we would probably stick with a Highway tyre and gain a small increase in comfort and wet weather performance.
Likewise if the majority of our time was spent trailering the car to traction competitions or hill climbs we would go with the Muddy’s.
We choose to run All Terrain tyres because we find they are the best compromise between comfort and performance. Dirt can build up quickly in Highway tread and lose a bit of grip off-road, where Mud Terrain tyres can be noisy and fling rocks up, breaking mirrors etc. A/T’s are sturdy, run nicely on the highway and provide good grip off-road.
One other type of tyre often overlooked are light truck tyres which are made to take plenty of weight, generally offer fairly deep and open tread patterns, sturdy sidewalls and their durability can offer great bang for your buck. Sorry, no raised white lettering on the sidewalls.
Fat or Skinny?
A 4WD Troop Carrier we owned came to us with great big, fat, 13inch wide, all terrain, earth munching horrors. We pulled them off and sold them in about 7 seconds to someone who really wanted big fat tyres for the soft white Western Australian beaches. We were heading for the gnarly stakes and rocks of the Pilbara and Gascoyne and opted to revert back to split rims and tubes. We fitted new 235/85R16 tubeless tyres and ran them with tubes.
Basically a 235/85R16 tyre is about 8 inches wide. Well, we marched the new tyres down to the same white sandy Western Australian beach we had driven on the day before. Guess what? The new skinny tyres got up and running in third gear. The fat 13’s could only manage second gear the day before. The car turned easier, and didn’t wallow through the sand like a fat cow, but rather cut down to cooler, harder sand and just hummed along (cold sand tracks better than hot). The suspension reacted faster and the ride was a lot more relaxed and unlaboured. The guy who bought the fatty’s got a bargain. Raised white letters as well.
On deep sandy tracks wider tyres can be problematic, riding high up the wall of the ruts rather than cutting down to the compact tracks at the bottom. Likewise, picking through rocks and around tree stumps or branches. The sidewalls of tyres are a weak point and are vulnerable to staking. Narrower tyres are more agile and adept at driving around things that could cause a wide tyre trouble. Narrow tyres can generally keep more rubber on the ground because they spend less time trying to straddle obstacles. Driving on tyres that are too wide is an exercise in brute force. You wear yourself, your passengers and your vehicle out because you spend the day bouncing off things instead of driving around them.
We are currently running eight inch wide tyres on tubeless rims. Eight inches is the absolute maximum we travel on. It is a comfortable width on the road but still agile enough to dodge the nasty stuff.
And finally to debunk an old myth. Decreasing tyre pressure will aid any situation where your tyres are spinning and you need more traction, whether it is rocks, hills, mud, river crossings and most especially – hungry deep sand. You gain traction because the front to back footprint of your tyre increases as the tyre deflates and begins to act more like the tracks of a bulldozer. Not because your tyre gets wider. Bulldozers go anywhere and it's amazing where a 4WD will go with lowered tyre pressure. We have driven out of truly horrible places with as little as 8psi in each tyre. Normally dropping down to 22psi or so is enough to get you moving along and sometimes 18psi or even 12 psi is required. Driving out of a situation is generally the best way to recover any car.
Decreasing tyre pressure will also make any rutted, gutted, potholed, corrugated track twice as comfortable for you and your car. It usually means you are able to travel in a higher gear about 15km faster. Lower tyre pressures also minimize damage to tracks and bush.
Quality and Price
It is no surprise that building tyre factories and paying wages in Australia, Europe or the USA costs a heap more than making them in Malaysia, India and China. Likewise massive and sustained advertising campaigns are expensive and get financed every time someone buys a new tyre.
Just because a particular brand of tyre is made in Europe or America and costs 30 percent more than its nearest competitor doesn’t automatically make it the greatest tyre for you or us.
We currently run a big name American made tyre on tubeless rims. Our previous tyres were a lesser known brand made in China fitted to split rims. At this stage it looks like the Chinese tyre will do more kilometres than the USA tyre is going to. It is doing it more comfortably on bitumen, with a bit less body roll when cornering and seems to have a bit more bite in the dirt.
Nothing major but the American tyre costs $450 more for the set. I want an improvement if I’m going to pay $450 more. That doesn’t make the American tyre bad it just means the Chinese tyre was great value.
The quality of a tyre can be judged by the sum of its parts. Tyres are made of rubber. High speed race car style tyres are generally made from a soft compound that allows them to get tacky and hang onto the road. They also wear faster. Typically the rubber in an all terrain or mud terrain tyre will be firm enough that you shouldn’t have to worry about premature tyre wear. Check the tread depth of a new tyre. Deep tread and lots of rubber should equal lots of kilometres.
Look for a high ply count in the tread area. Tyres are made by a lamination process from steel and polyester belts. Each layer is called a ply and the more you have the more resistant the tyre is to punctures. I would avoid a radial tyre with less than 6 ply for regular off-road work and aim for something with 10 - 12.
Sidewall ply ratings are important also, although rarely discussed at the tyre shop or promoted by the manufacturers. Buying a tyre with more sidewall plies gives a stronger resistance to staking and can provide a slightly stiffer ride for really heavy vehicles.
Of course, strong sidewalls help to hold up that Big White Lettering.
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