Dear all

I am working in the northern part of Ghana, where we mostly drive on gravel roads. We are driving a Toyota Landcruiser (HZJ 105 L).

My problem is that I'm unsure what pressure to run in the tires. The tire size is 235/85 R16 (Bridgestone A/T) and the manual states 2,6bar (38psi) in front and 3,75bar (54psi) in the rear tyres.

The Ghanians keep telling me that the nature of their roads means you need to run low pressure, and I keep insisting that low pressure is for sand, and that on the hard gravel roads here you should follow the manual. However I am now starting to doubt whether I'm right.

Is there anyone out there who can help me?

Thank you very much in advance
Thor

You're right. Normal convention is high (standard) pressure on gravel/rocky surfaces. This will reduce the damage of pinch punctures/rim damage.

You may need higher than standard if the vehicle is heavily loaded.

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Fraser

As with most questions there are multiple permutations that affect the answer.

Lower tyre pressures can result in fewer punctures due to sharp stones/gravel. Unless of course you are either travelling so fast or are unobservant such that you hit a large rock hard enough to cause a compression cut/puncture or even wheel damage.

You can avoid side wall damage or compression cuts by driving slowly over large rocks with the centre of your tyre.

On gravel I run my LWB G Wagen (no light weight!) at around 20 to 22psi all round for exactly the reason to try and avoid punctures. Sand around 12-14psi. Seems to work for me.

In "normal" use (e.g., 2 wheel drive car on gravel roads in North America), pinch flats and dented rims are not a concern. Under these circumstances, higher inflation pressures run more risk of flats due to sharp rocks puncturing tire treads. The risk is particularly acute immediately after road grading, which turns a lot of stones on edge, and wherever the local stone tends to fracture into flakes (for obvious reasons). Back in the dark ages before radial tires became the norm, the feedback loop was quite obvious: hard tires + recent grading = lots of flats/soft tires = few flats. These days, with radial tires everywhere, it's less obvious but still operative. Obviously, speed is also a factor.

This might be what your Ghanian friends are talking about. Or not. I don't really know what this "normal" state of affairs might imply about the specific roads you're driving or the tires you're using. I'm just offering a different set of date points for your consideration.

enjoy,

Mark

Edit to add: cross posted with RussG

One more for soft tyres on gravel. Definitely less punctures IMHO

Also a more comfortable ride, the soft tyres will absorb a lot of the bumps.

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www.4x4-travel.co.uk

With the tyre pressures you are talking about, it seems like your vehicle is very heavily loaded!

I drive a 80 series LC and use 2.5 all round for tar, or 2.2 for gravel. I drop it to 1.8 for rocky gravel and 1.2 for sand with 25% more in the rear if I'm loaded.

However, if you are not getting punctures, and your tyres are lasting sufficiently long, then there seems to be no need for change.

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Dawie du Plessis
www.pictureafrica.org
www.photographersa.co.za

There are lots of opinions on this but I also run a HZJ105 and found on gravel sufaces it runs at it's most comfortable at 1.8 bar, no heat build up and still good handling. North of Ghana has those dusty red roads filled with potholes, the softer tires will absorb most of the impact giving you a more comfortable ride.

Just don't go below 1.8 on the front if you are travelling high speed, the 105 likes understeering and being permanent 4wd it can become a handful in a corner.

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Jean Visser

http://ons4.reproroom.com

Thank you all for the many responses, I’m amazed that so many have contributed.


The roads we have up here should perhaps be called dirt roads and not gravel roads, I don’t know if there is a difference between the two terms? But as Jean Visser writes the roads in northern Ghana are dusty red roads with plenty potholes, and also quite a bit of corrugation. I have never experienced a puncture here due to sharp stones…..but then again that might be because the grater rarely passes by. The one puncture I’ve had for the last year was due to a nail.

“If you are getting the mileage you want and not many punctures, who are we to say that you're doing anything wrong?” The tires have lasted 25.000 km now and need to be changed soon, I’m not sure if that’s sufficient, but it seems okay considering that they do so many Km’s on dirtroad. More important is that they are not worn unevenly on the sides or on the middle, so I guess that’s a sign that the pressure I’m running is ok.

“How heavily laden are you running?” – I usually don’t travel with significant load, besides the passengers. – Oh and the tires are tubeless!


Lastly I wasn’t clear enough in my first post - The argument between the Ghanaians and myself about high or low pressure was mainly about stability/safety on the road, and the fact that they believe high pressure will make the tires explode because of the heat (the last one I already ruled out).

As it looks for now, I think I’ll keep the pressure as the manual states, maybe experiment a bit with lowering it for comfort on the corrugation.
Once again thank you all for the many inputs, and thank you for a great forum.

Cheers
Thor

25 000km is not a lot! On decent off-road tyres you should be getting 2 to 3 times that at least...

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Dawie du Plessis
www.pictureafrica.org
www.photographersa.co.za

So much of this is subjective! Speed, load, tyre construction, aspect ratio, road surface all play a part.

Ask the tyre manufacturer. they should know

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Fraser

I agree, we just finished going up and down Africa with one set of BFG Muds, 68 000 km's and a lot of abuse!

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Jean Visser

http://ons4.reproroom.com