Tyre Pressure: Thoughts on constant loads

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drew3
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Tyre Pressure: Thoughts on constant loads

Post by drew3 »

Hi all looking for some advice regarding long distance tar driving (tar, long distance) tyre pressures and constant loads. Not 4x4 or off road related.

The manual suggests the tyre pressure on my lux should be 2.1 when not loaded. I normally put them on 1.8 as I drive on dirt/gravel for 30-40min before I hit the tar, and I have learned over time that it takes 30min for my tyres to heat up and increase the pressure to 2.1 so I am on the recommended pressure when I hit the tar (tried and tested). I have 30x9.5 BFG AT's on my Lux.

Now my question is, does the recommended tyre pressure account for the mass of passengers and other stuff? Between my better half, my dogs, my tools and I, we probably make up 200kg of the 800kg my car should be able to carry - a quarter.

I have been taught (working on game reserves and farms) that you should increase tyre pressure by 0.2 for every for 100kg loaded. Is this accurate? It would suggest that my tyre pressure should be at 2.5 all round to account for the extra 200kg we normally drive with.

Thank in advance.

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Re: Tyre Pressure: Thoughts on constant loads

Post by Mud Dog »

Pressures vary a little between tyre brands / types and sizes. While 2.1 sounds fair, what is the wear pattern on the treads?

If there is more wear in the middle, then the pressure is too high - too low if there is more wear on the outer edges. Remember also that front and rear will wear a little differently.
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Re: RE: Re: Tyre Pressure: Thoughts on constant loads

Post by drew3 »

Mud Dog wrote:Pressures vary a little between tyre brands / types and sizes. While 2.1 sounds fair, what is the wear pattern on the treads?

If there is more wear in the middle, then the pressure is too high - too low if there is more wear on the outer edges. Remember also that front and rear will wear a little differently.
I have a little over 30 000km on these tyres, and the wear pattern seems pretty even at face value.

Regarding front and rear tyre wear, I rotate the tyres every 10 000km.

Any thoughts on the idea of increasing pressure by 0.2 for every additional 100kg loaded?

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Re: Tyre Pressure: Thoughts on constant loads

Post by Mud Dog »

I've heard of this before and have paid it little mind - generally running at 2.1bar I have found that the tread tends to wear a little more in the centre which indicates over inflation anyway. If your tread wear is fairly even I would stick with what you're doing.
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Re: Tyre Pressure: Thoughts on constant loads

Post by CasKru »

I would say use the manufacturers values as a guide and calculate the values.
For example if your vehicles weight is 1500kg and the tyre pressure for the empty vehicle is 2.1, and your max load is capacity is 1000kg and the tyre pressure for max load is 2.7, calculate the amount to increase pressure per 100kg.
2.7 bar - 2.1 bar = 0.6 bar
1000kg / 100kg = 10
0.6 / 10 = 0.06 bar

So in other words you would need to add 0.06 bar for every 100kg.

But keep in mind, typically the front and rear have different values for empty and full loads, especially with bakkies. So the front value could be 2.3 / 2.7 and the rear 2.1 / 2.9 which will then give you different values per 100kg. In this example it would be 0.04 bar for the front for every 100kg and 0.08 bar for the back for every 100kg.

Hope this helps a bit
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