Offroad driving myths busted
There are plenty of myth-conceptions when it comes to driving off-road. here are some offroad driving myths, busted – Bet you’re guilty of at least one…
RECEIVED WISDOM is advice passed down and then along. And almost nobody ever questions it, and more often than not the advice actually, kind of seems to make sense. Only mostly it’s total rubbish, or stuff that was true during the middle ages, but not now…
Here’s a few things that you often hear bandied about in off-roading circles that are wrong:
- High tyre pressures help the tyre ‘cut down’ through mud to find traction – in some very specific cases that may be true, but mostly it’s not. High (road) pressure tyres will sink into the ground, which increases resistance to vehicle movement. Reducing tyre pressures will increase the effort required to turn the tyre as there is more tyre deformation, which is why high tyre pressures are used to reduce fuel consumption when driving on bitumen. However, reducing pressures will increase the contact patch which will mean the tyre doesn’t sink in as far when on soft ground. That will outweigh the extra effort to turn the aired-down tyre, so in soft conditions air down to reduce rolling resistance. All this is explained by the science of terramechanics.
- Don’t drop tyre pressures for rocks – the rationale here is that the tyre sidewall bulges out and will get damaged. In fact, the bulge is tiny (I’ve measured it, see the 4WD Handbook for the results) and thus the increased risk of sidewall damage is tiny. On the other hand, reducing pressures makes the tyre softer so less prone to punctures, there’s less bouncing so better traction, and the tyre grips odd-shaped rocks much better. The tiny loss of ground clearance is well worth these advantages. In short, air down for rocks.
- Wide tyres have a greater contact patch – nope, same as narrow, just a different shape. Narrow tyres have a long and thin patch, whereas a wide tyre has a short but wide patch. Narrow tyres have lower rolling resistance than wide so are generally better for offroad and fuel economy. Wide tyres have better cornering grip, in general, but that’s not because of a greater contact patch area.
Read the rest of the Myths on 4×4.practicalmotoring.com.au.