AT Tyre Pressures vs OE HT Fitment Pressures

[Miner]

Is there any difference? Just a thought as they are a more sturdy tyre so may need less air?

Apologies if this is guff but my logic comes from bike tyres... e.g. I run Dunlop slicks which are a hard carcass tyre and need much less pressure cold and hot vs something softer like a Pirelli slick.


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[hinsch]

I run the same pressures HT/AT tyres normally about 38-40psi front and rear, unless your towing something about 1700kg then bump the rears up by 4-6 psi.

[old Jack]

According to the Toyo Load Infaltion Tables you need more air in an LT construction tyre than a Passenger construction HT tyre to carry the same weight.

A P265/65R17 110 tyre at 35psi is rated to carry 1062kg per tyre.
A LT265/65R17 120 tyre at 35 psi is rated at carry 802kg per tyre but a 50psi it is rated at 1031kg per tyre so for almost a 50% increase in pressure you only get a 25% increase in load capacity. So based on this you could logically draw a conclusion that Passenger construction tyre's are stronger than Light Truck construction tyres.

However this is not the case, LT tyre's are much stronger and more heavily constructed so they are a much tougher tyre for high load and poor road conditions.

A Gen 4 Pajero has a maximum front axle load of 1320kg (normal weight is about 1200kg) so this is shared between the 2 tyre's so that is 660kg a tyre, the maximum rear axle load is 1800kg (the normal empty weight is about 1100kg) so that is 900kg a tyre. So you can see that if you have your tyre's inflated over 35psi then you have well truly enough air in the tyre.

Running overinflated tyre's is less comfortable and puts more load on your shockers and bushes, and handling can be negatively effected if a tyre is really over inflated. However it does give you slightly better fuel economy and in some cases where the suspension is soft it can offset some uneven wear of tyre's because of the changing wheel alignment of the independent suspension when loaded.

Running tyre's on minimum pressures results in a more comfortable ride, but will result in increased fuel consumption, uneven tyre wear and poor handling.

So what is the "Goldilocks" pressure?
From my experience it is the factory coild inflation pressures stated on the tyre placard plus about 10% to 20%, and keeping an eye on the tread wear across the complete width to ensure it is even. Regular rotation and balancing extends the life of your tyre's, 10,000km intervals for HT tread tyre's are fine, 7,500km for mild AT tread patterns and 5,000km for aggressive tread AT/MT tyre's if you want to get the most wear out of your tyre's.

OJ.

[Miner]

Thanks OJ... thought this wouldn’t be a straight answer... as a rule of thumb are AT tyres also softer compound than HT?

I normally run at the normal pressure settings for up to four people as it’s often just me in the car, always good wear to date. Run at max load pressures when towing the bike and quad, IRO 5-600kg. Seems to be ok to date.

First set of AT’s, Geolandar AT-S, harder on fuel and noisier but relatively cheap, look the biz and great off-road. Good for the dunes as not too stiff in the carcass like the BFG’s. Don’t see them lasting 60k+ like the HT Duallers did though.


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[old Jack]

What load index are the ATS?
Passenger or Light Truck construction?

OJ.

[Miner]

They are listed on the Yokohama website under passenger tyres...

https://y-yokohama.com/global/product/tire/tires/passenger/geolandar_ats/

Load rating is 112(T)


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[old Jack]

They are listed on the Yokohama website under passenger tyres...

https://y-yokohama.com/global/product/tire/tires/passenger/geolandar_ats/

Load rating is 112(T)


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Thanks Miner.

If you check the side wall you will see what the maximum cold inflation pressure is, I suspect it is 44psi. So do not exceed this this max pressure if you want yo run high tyre pressures.

OJ.

[Miner]

Thanks. I was thinking more for normal driving... 2&2.2 bar F/R best for normal use and wear on the Dueller HT. Don’t go above 2.4&2.8 (2.8 ~ 41psi) though when towing as it’s under the unbraked limit for the vehicle.

Incidentally they grip and hold the bead well at around 1 bar / 14-15psi on the dunes. [emoji1360]


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