During the really cold snap we had, you may have heard people discussing the merits of four wheel drive and the potential for an 4×4 to really shine in bad weather. However, do you know how it works or have the merits been advocated to you without an understanding of the technology? It’s not perhaps quite as simple as that due to the fact that no two manufacturers seem to fit the same system, however, we will look at the ‘basics’ and consider manufacturer specific developments in later articles.
Engineering it in
Taking an example of a front wheel drive car because it is most common on our shores, your car is set up with an engine, a transmission, a front differential and a front drive shaft. These are all key components in sending power to the ‘driven’ front wheels. In four wheel drive, there’s a transfer case (the important thing – this transfers power to the rear wheels), a rear drive shaft and a rear differential. This further engineering allows the rear wheels to also be driven, thus the engine is making all cars rotate with power.
Why does it help?
This is the simple part. Sticking with the front wheel drive example, if you try to put power down and you have no traction, the front wheels will spin. Because the rear wheels are not driven at all in our example, they won’t move an inch. If they were driven, you have an extra chance to gain traction on the ground and drive away.
Is it on all the time?
This tends to be manufacturer specific. Some systems operate permanent four wheel drive, however others will activate only when they feel slip. The car will try to regain traction by sending power to the normally non-driven wheels (probably the rear!).
When does it not help?
Four wheel drive will not help at all when it comes to stopping. The best way to ensure you have optimal stopping power is regularly servicing your brakes to ensure they are in tip top condition and having tyres fitted that are most suited to the conditions you are driving on.