4WD offers improved traction and handling in slippery driving conditions such as mud, ice, snow, and rainy weather. Since all 4 wheels are driving the vehicle forward, it will be more stable on slippery surfaces.
BUT WAIT!!! Unfortunately, there are limitations to the level of traction you can expect from your 4WD when road surfaces are slippery. This article will discuss the pros and cons of driving your non-permanent 4WD on wet highways and if there is a risk of damage in the long term.
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Does 4-Wheel Drive Help in Rain – TRACTION
I remember my first wet road experience when I drove my first 4WD in the rain, I was not sure if the road surface was slippery enough to warrant me safely engaging the 4WD function in the rain. I remember wanting the road to be as slippery and wet as possible because I was so paranoid about drive-train binding. Being a newby 4-wheeler at the time I didn’t quite understand how the drivetrain binding occurs and which situations could bring on this effect. So, I just never engaged 4WD and drove super carefully.
Fast forward to today and, as a matter of fact, I still don’t engage 4WD in the rain since I’m driving a non-permanent 4WD. When you have a permanent 4WD or AWD you have the advantage of having all 4 wheels being propelled by the drivetrain and transfer case. This is one massive advantage of an AWD and a permanent 4WD over a non-permanent 4WD truck. But, more about that later.
So with a 4WD, you can engage 4H in the rain, which will greatly assist with traction, however, you need to determine if the added improved traction warrants risking damage to your drivetrain if you are driving a non-permanent 4WD. The way I see it, yes you do have the functionality to improve safety through added traction, but won’t it be better to adjust your driving style in the rain instead?
As mentioned from the outset, many 4-wheel drivers have found themselves in a situation where, because they have a 4WD, they fail to adjust their driving style in the rain and end up causing an accident. You are better off slowing down and increasing your driving speed and following distance than engaging 4WD in the rain. Why?
How Does 4WD Drivetrain Work in Rain?
So when you engage in 4-wheel drive, the vehicle doesn’t know it’s driving in rain or snow or mud or sand. These are all low traction, slippery driving surfaces but they all need to be driven on differently. A rainy day creates a lot of slick and greasy road conditions.
Now with 4WD engaged on a highway or dry pavement, you expect the traction level to improve, which it does, however, it doesn’t help much with stopping, which is the highest cause of road accidents in winter months when roads are slippery and wet with snow, rain, and ice.
4 wheel drive assists you with pull-offs and does assist with keeping the vehicle more stable. Cornering, however, is not improved by much and if you accelerate in a bend or are overconfident on a windy wet road, it makes no difference if you are driving a 2 wheel drive, All Wheel Drive or 4 Wheel Drive, since once the traction is lost, it’s lost, and you are at the mercy of the laws of physics.
In fact, the only time when a 4WD will prove beneficial in the rain is when you apply the same rules of safe driving to a 4-wheel drive the way you would to a 2WD vehicle. Only then, you can confidently say, yes a 4WD is safer on wet roads than a 2WD. It does not give you a license to be overconfident.
How Does Rain Affect Traction?
One of the biggest threats to drivers on a wet slick road is hydroplaning. Hydroplaning, limited visibility, decreased traction and speed are all reasons why accidents happen in the rain. And when you combine them then it’s the perfect recipe for a crash.
There are a few factors that cause limited traction on rainy days and they are:
|Rubber Compound of the Tires
|Road Surface Traction
This table illustrates how tire pressure, rubber compound, road surface traction, and speed might be related in a hypothetical scenario.
Any one of these can aggravate driving conditions and cause a driver to lose control of a car.
When the tire pressure, for example, is pumped up too high on a wet road, you are decreasing the ability of the tire to make maximum traction with the road, resulting in only the middle section of the tire providing traction. An overinflated tire will behave like a narrow tire with limited traction. The surface area of the tires, which Is meant to provide traction is decreased, thus limiting the surface area between the tire and the road.
This can also cause your tire to behave differently by feeling rather bumpy and not absorbing any differences in an uneven road, but rather bumping over them. When a tire is not making solid contact with a road, traction is lost easily, combine this with a wet road and you have yourself a disaster in the making.
The Rubber Compound of Tires
This is another reason why traction can easily be lost on a wet road, and that is if you are driving with a very hard compound tire. Hard compound tires are not designed for comfort or superior traction, but rather for longevity and high mileage. They do offer adequate levels of grip for general driving conditions however when the rubber compound is hard, it does not bend, grip, or flex as well as a soft or medium compound tire.
Road Surface Traction
This plays a major role in the extent of traction your 4WD has in both wet and dry conditions. A smooth surface will create a slippery low traction condition for any vehicle, 2WD, AWD, or 4WD. Highways are usually made of a coarser tarmac to provide maximum grip under most conditions.
Speeding on a rainy day is just asking for trouble. It’s the number one killer in the winter season yet people fail to adhere to all the warnings. When the weather deteriorates and road surfaces are wet, decrease your speed immediately. It’s irrelevant what the maximum legal speed is at that time since that could even be too fast for safe driving under challenging driving conditions.
Increase your following distance and switch on your headlights when visibility is limited. Obey the guidelines from the traffic notices and listen out for any announcements about hazardous situations to avoid. Never speed in the rain.
Does 4-Wheel Drive Prevent Hydroplaning?
When it rains, the water on the road surface makes the road slicker and more slippery. The tarmac used in highways is designed to provide adequate levels of traction under most driving conditions i.e. wet weather, dry weather, and snow. Also, most highways are designed at a slight angle to allow drain-off and prevent water build-up and dams of water collecting on roadways. Engineers are constantly coming up with improved methods to improve water drainage from highways.
However, hydroplaning is still a realistic hazard, so let’s look at how we can avoid it and what to do when it happens to us.
So when you are affected by hydroplaning your vehicle will simply continue moving in the direction it was going at the time of the hydroplaning happening. This is because the inertia will simply cause the vehicle to skid in that direction until traction is regained or until the vehicle stops. This effect happens within seconds and usually lasts for a few seconds. A few seconds could, however, prove long enough to cause you to lose complete control of the vehicle if you don’t react correctly. You could be sent careering off the road into a barrier or worse.
When You Should Use 4-Wheel Drive
4WD should only be used when road conditions are bad and traction is low. This can be any surface ranging from:
- Sleek roadways caused by ice build-up
- Snow packed roads
- Water Crossings
- Muddy tracks
- Sand roads
- Dirt roads
Any of the above-mentioned environments are perfectly safe to engage in 4-wheel drive. You as the driver need to learn to read the road surface when you own a 4-wheel drive.
Yes, I am well aware that you are not required to select neutral and lift off the gas first, but this is the safest way to engage 4H from 2H if you intend on keeping the 4-wheel drive for a long time.
Safety is improved with a 4WD on low traction surfaces and you have the added capability to explore unchartered terrain with confidence. Driving on the roadway with 4H engaged is done at its own risk since the driver needs to determine if the surface is slippery enough to truly warrant 4WD mode on a high traction surface such as a tarmac road or a dry pavement.
If you have 4A, use that instead, I would rather err on the side of caution and adjust my driving style, decrease my speed, and increase my following distance instead.
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