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 Post subject: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Mon Aug 20, 2012 9:24 pm 
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Joined: Fri Jul 23, 2010 8:35 pm
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Hi all,

Seen the post about the "terrible state the gravel roads are in" and wondered why it shouldn't be mandatory to deflate your tyres:
* Less corrugation
* people will drive more carefully as not to damage their tyres
* people will generally drive slower

Except for the enforcing part it seems like this is an easy win. Or do I miss something?


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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Mon Aug 20, 2012 9:39 pm 
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I am no expert, but what wouuld we then do on the tar roads, because the air for the tyres is at the camps, and the camps all have tar roads around them, before you can turn off on to a dirt road...............or am I missing something. :whistle:

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Mon Aug 20, 2012 10:08 pm 
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There is no problem driving on tar roads with deflated tyres (f.e 1.5 bar). They might wear out a little but it is perfectly safe. So you can inflate them again when leaving the park


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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 9:25 am 
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MM,

The best tyre pressure depends on the type of tyre (Side wall thickness and flexibility).
The tyre size (Deflating low profile tyres will damage your rims before it helps to soften the ride).
The load you are carrying or if you are towing (The standard tyres on a land cruiser, the marie biscuits, can be pumped to 3.5bar if loaded so 2bar is deflated on those tyres). Other tyres you can drop down to 1.5 bar or even 1bar and still be fine while driving slow. On sand, I have deflated to 0.8 bar before.
The speed you want to drive once you are back on tar. Dont deflate your tyres for the day you are leaving the park. It is extremely unsafe to drive with deflated tyres at highway speeds.

Sorry for making your question more complicated :redface:

Deflated tyres will also increase fuel consumption.

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 9:28 am 
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I agree with MM. There are many differences between Kgalagadi and Kruger Parks.

Kgalagadi has one "main" gate at TR and a petrol station with facilities to deflate and inflate tyres. The other gates are not used by many vehicles (MataMata also has a petrol station). There are far fewer vehicles per day and very few day visitors in KTP. All the roads are sand, so no worries about tar roads - you just deflate on arrival and inflate on departure.

KNP has 9 gates and not all of them have petrol stations nearby. With the sheer number of vehicles per day it would, as MM says, be a nightmare to provide facilities for deflating/inflating tyres and policing it. Also - what about delivery, staff, police, army vehicles etc.? Also some vehicles won't be going on the sand roads and will stick to the tar - how do you decide which vehicles must deflate and which not?!

Nice idea noeg, but probably too difficult to enforce.

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 1:23 pm 
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Joined: Sun Aug 23, 2009 11:43 am
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Location: Israel
hi,

deflating tyres is used mainly while driving on sand dunes and sandy roads and while returning to dirt or tar roads one must inflate back the tyres. deflating tyres has no affect in regard to firm dirt roads or tar roads.

On the contrary - on tar and dirt roads the tyre may over heat and even explode if used in this way for a long time (if someone is visiting the kruger for more than a few days).

in addition in small and regular cars the steering may became more difficult which may cause new or unskilled drivers problems in steering, which may also be unsafe for other drivers or padestrians.

in addition, no one can make me or any one else to wear out the car tyres and cause damage to the car. also note that alot of the cars in KNP are rented, and if returned with wear out tyres the agencies might demand fines and stuff...

to some up - if the purpose is just to make drivers drive more slowly - there are other more safer ways than causing cars to wear out their tyres - with no real need.

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 2:11 pm 
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Thanks homer.s . Iagree, the type of road surface in Kruger would not benefit from deflating tyres, while in the KTP they do make a huge difference. :thumbs_up:

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 2:23 pm 
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Does anybody know how corrugations on dirt roads are formed? It was in one of the quizzes a year or two ago.

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 2:39 pm 
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I have to disagree slightly. If you have the type of vehicle with tyres that allow tyres to be deflated it is definitely a good idea to do so for the corrugated roads in KNP. I deflate my bakkie tyres down to 1.6bar in the park and then I hardly feel the road. On a car I will probably go down to 1.7 if it is not a low profile. Deflating a tyre can improve the ride comfort significantly, especially if the road surface is badly corrugated.

For a tyre to blow out at 30km/h you have to deflate it way too much and probably to about 0.7 bar and drive all day without stopping. The heat comes from the constant flex in the side wall, so just dont over-deflate they all should be fine while driving at low speads.

I do it to improve ride comfort and it definitely makes a big difference. When I leave the park and return to driving at speeds exceeding 50 km/h I inflate my tyres to what it should be. I do carry my own compressor for this so I dont have to wait at the filling station. :thumbs_up:

Thread wear is not something I would worry about as it will only become a problem if the wheel alignment is off and then the tyre pressure is not the real problem. Fuel consumption is however effected when driving with deflated tyres.

A good rule of thumb to make sure you are using the correct tyre pressure for the load being carried is a difference of 0.3 bar between cold pressure and hot pressure.

Rooies,

Here is a good explanation to your question,

http://www.abc.net.au/science/k2/trek/4wd/Overcor2.htm

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 4:37 pm 
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It would seem that the tail is trying to wag the dog :doh:

Corrugations on a sand and/or gravel road are more often caused by poor shock absorbers than inappropriate tyre pressures. While tyre pressures may make a difference to the COMFORT of people in a vehicle, they will make little difference to the damage and further corrugations created by poor shock absorbers / weak vehicle springs AND relative vehicle speed.

This is a rather obscure discussion, and a greater understanding on the theory of "waves" is required to fully understand the reasoning behind the creation and further development of such corrugations on sand and gravel roads. The creation of corrugations on such roads is a function of shock absorber efficiency, spring tension, tyre load, tyre pressure, tyre "give" and tyre size, and most importantly, SPEED of vehicle. By simply altering your own vehicle's speed on any corrugated road, you will alter the characteristics of your vehicle on these corrugations, and either increase the damage already caused to the road or not. However, finding the happy medium where no further damage is caused is not an easy feat.

Simply lowering the tyre pressure may create more comfort but is unlikely to reduce the damage being caused by all the other factors mentioned above.

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Tue Aug 21, 2012 6:01 pm 
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I drive a Landy Defender , and under normal circumstances , it has a general " rough" ride , even sometimes on a poorish tar road. Generally , I drive about 3500 km per month , of which up to 40 % can be on dirt roads . I therefore do not as a general rule deflate my tyres for every old dirt road , but for better grip , would rather use the dif-lock , and unlock again when back on tar .
Now , in Kruger , the dirt roads are quite often quite corrugated , and at slow speeds , you certainly feel it in that Landy . I therefore on arrival in Kruger , deflate my tyres down to about 1.8 bar or so , and find that , especially early morning , when tyres and road is still cool , it does improve the ride . Later in the day , it becomes more bumpy again , but still not as bad as when tyres are not deflated .
The reason for the easier ride , is because the contact surface between tyre and road is much bigger/ larger with deflated tyres , and as such then gives a softer ride .
I therefore deflate my tyres because of the general bumpy ride , but there is no real reason why you should deflate your tyres when driving a normal " soft-roader " or sedan car . Modern suspension sytems are specifically developed to take those bumps out for you , and therefore make the ride easier .
There is however also a downside to the modern suspension system . It allows the wheel itself to move up and down whilst at the same time the car's chassis remains level - that's why it is called " shock-absorbers " , and it works in combination with springs , which again allows the body/chassis to move up and down more gently than the wheels itself .
Now , the downside is , the bouncing/spinning wheels , causing the road-surface to wear out in bumps .Up-and-down , up-and-down ....... This is made worse by the air-movement , or air-suction by the vehicle , which sucks up the fine dust behind it , and exacerbates the corrugation ( Think of the ripples made by wind on desert sand or beach sand ) .
So , high speeds do worsen corrugations .

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Wed Aug 22, 2012 3:05 pm 
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The nature of a internal combustion engines functioning creates corrugations due to the reciprocating combustion cycle - this is aggravared by road undulations and the resultant increases and decreases in vehicle speed assisted by driver initiated acceleration and deceleration .

Were all cars electrically powered there would be very few corrugations .

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 Post subject: Re: Why isn't it obligatory to deflate your tyres in Kruger
Unread postPosted: Wed Aug 22, 2012 3:12 pm 
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Txs Ndloti
(btw lectrical cars would be a blessing in Kruger)

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