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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:

  1. 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.
  2. 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.
  3. 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.


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Ziggy
Ziggy
5 years ago

TC in sand: I’ve read differing views on this but now have done quite a lot of sand driving inc in some very soft stuff at Robe, leaving it on. Rarely had a problem.

Robert Pepper
5 years ago
Reply to  Ziggy

I’ve read differing views on it too. And I’ve got the experience across different sands, countries and vehicles to back up my opinion so I wrote what I wrote 😉

Elliot Cook
Elliot Cook
5 years ago

100% using snatch block changes the load on your Winch. Correctly set up, the Winch will pull on its rope twice as far with half the resultant force vector on the anchor point. It’s a simple concept utilised for hundreds if not thousands of years. Research the block and tackle. I can’t believe you’d assert that it doesn’t. I’m dumbfounded haha. Yes there are ways to use it where it doesn’t do so, but these are different utilisations of the tool

Robert Pepper
5 years ago
Reply to  Elliot Cook

The point is it doesn’t always give mechanical advantage. “Correctly set up” may also be a simple redirect with no MA by intention.

Elliot Cook
Elliot Cook
5 years ago
Reply to  Robert Pepper

my bad i had to double check this. i thought it mean never gave the MA. Its simply saying what im saying, that there are way that it will and ways that it wont. myyy badd… skim reading haha. (still a stupid thing to put in the list, its a sorta obvious fact)

Robert Pepper
5 years ago
Reply to  Elliot Cook

That’s ok, most people comment first read later (if at all).

If you know how pulleys work it is obvious but I can assure you many do not. Hence it’s here as a myth.

Clark McConachy
Clark McConachy
5 years ago

I agree with most of these if you are just talking about weekend off roading. I would never go touring in a petrol automatic however. 2 points I disagree with strongly were not points but comments in them; Skinny tyres are shocking offroad and even worse on dirt roads, speaking from plenty of experience. Leaf springs are NOT cheaper than coils, not even close. Don’t believe me? Ask the owner of a 40, 60 or 75 series. They’ll back me.

Robert Pepper
5 years ago

Petrol automatic 4WD drivers…chime in. Can be done.

We’ll need to agree to disagree re tyres. 235/85/16s on Defenders…nice rubber.

Leaves – meant to manufacture/design not aftermarket. Remember the leaf spring is both an axle positioning system as well as a spring. For a true comparison of manufacutre cost you need to include whatever systems are used to locate the coil spring. I will clarify that point.

trackdaze
trackdaze
5 years ago

Whilst its true in dependant suspension will have higher static clearance. But the ground clearance is variable and will tend to bottom at less than optimal moments. It also doesn’t allow for leverage across the axle which will keep the body much more level.

Leaf springs tend to be more expensive to buy.

And I leave my traction controlled centre diff open( torsen) on easy going sand. Lock it for heavy going

Robert Pepper
5 years ago
Reply to  trackdaze

*may* bottom at less than optimal moments…and typically doesn’t get any worse than a live-axled equivalent. Refer below on comment for leaf cost.

Noreen Reeves
Noreen Reeves
5 years ago

Hmmmm Im the wife and I drive my FJC every day. 100km every working day and longer on the weekends. I wonder what bad habit I AM supposedly teaching my adaptive gearbox? :o) (Mind you, Ive been teaching it those same bad habits for the last 4 years….)

Robert Pepper
5 years ago
Reply to  Noreen Reeves

Exactly Noreen! I’ve never heard a wife say her husband teaches a car bad habits. Doubt I ever will either, seems to be a male to female thing.

Chris
Chris
5 years ago

Why do you recommend not using nitrogen it the tyres?

fouros
fouros
5 years ago
Reply to  Chris

waste of time when airing down for soft sand or off road

Robert Pepper
5 years ago
Reply to  Chris

Chris there is a link to the full explanation in the article above. Basically fouros is correct, but even if that wasn’t the case the returns on investment are negligible. Just don’t bother.

Tony
Tony
5 years ago

I’d like to take you to task on the track / offset issue Robert. Most 4wd vehicles have a non zero offset. As an example a Toyota IFS Land Cruiser has a +60mm offset. I.e. near the outside of the wheels. If you widen the rims, then the track, being in the center of the wheels will narrow. For a negative offset wheel the opposite is true. Your statement is only true for vehicles that have a zero offset, and they are the exception rather than the rule. I did love you off road towing article though.

Robert Pepper
5 years ago
Reply to  Tony

Tony if the rim is made wider for the same offset then it gets equally wider on both sides leading to no change in track (but a change in width).

Tony
Tony
5 years ago
Reply to  Robert Pepper

Hmm, you are right.

Apologies….

Dan
Dan
5 years ago

tip 1 and 3
ok so if two cylinders have the same radius and length than they will both have the same contact patch (surface area touching the road), change either dimension and you change the contact patch if the contact patch increases than so does the friction caused by that contact. now we have that out of the way lets change cylinder with tyre. Now where talking tyers we have another element to include which is pressure. So for now we will keep the pressure the same on both tyres keep the radius the same but we will change the width of the tyre. The width of the tyre does not effect the front to back contact width dimension on a tyre but the the width of tyre will increase the length of the contact patch (same distance front to back but now longer therefore larger surface area). changing pressures in a tyre changes the size of the contact patch (less pressure = more contact area) hence increasing friction therefore increasing rolling resistance which leads to more energy needed to free that friction and get the said tyre rolling.
More rolling resistance means you have more friction this is great when 4X4 is selected as traction rules! not so good when on the black stuff as this means more power needed to break the friction and get the tyre rolling not to menchin more wear on the tyre. when driving sand you want to lower pressure to get a larger contact patch to stop the tyre cutting down or sinking into soft sand and instead act like a balloon and float over the sand.

Robert Pepper
5 years ago
Reply to  Dan

Dan – I think we agree but not entirely sure. Anyway thanks for posting!

ezytrail
4 years ago

If doing the exact amount of taking some radius and length with the present radius and length, what would happen then?

Robert Pepper
4 years ago
Reply to  ezytrail

I don’t get this ?

ezytrail
4 years ago
Reply to  Robert Pepper

I mean if you have put 5000 kg in this 4×4, is there any risk that can get?

Robert Pepper
4 years ago
Reply to  ezytrail

Still don’t get it sorry. What exactly is the question?

ezytrail
4 years ago
Reply to  Robert Pepper

Okay my question is, is there any risk if you get to load a very big weight in the 4×4?

Robert Pepper
4 years ago
Reply to  ezytrail

Yes. What Ern said – vehicle wil break.

Ern
Ern
4 years ago
Reply to  ezytrail

Yes. It will break the vehicle.

Fernando
Fernando
3 years ago

I disagree about the traction control is better in sand. I was. Lam digging and came back to my truck to find it had sunk down. I thought it wouldn’t be a problem especially since I have a rear locker. I got in tried it in 4×4 high no good. Now with the rear locker still no good then a guy trying to help said is the traction control on? I turned it of and hopped right out of the sand . The traction control was keeping the rear locker from working and holding back the torque. I never would have even thought about it. It was super fine wet sloppy sand not dry but not wet and packed. I thought I was going to loose my truck to the ocean. Fuck the traction control. I never got stuck in my 02 f150 that did not have traction control or a rear locker

Robert Pepper
3 years ago
Reply to  Fernando

What vehicle was this?

Make a differentiation between stability control, brake traction control and engine traction control. Stability control will activate engine traction control which is what will hold back the torque. Brake traction control just doesn’t do that.

I’ve also never seen a vehicle that doens’t disable engine traction control and ESC once a locker is engaged. So strange behaviour there.

Huw
Huw
2 years ago

The ‘Read the rest …’ link is broken – can it be found?

Robert Pepper

Robert Pepper