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What Pressure??? (and yes i did search)

Posted: Thu Sep 10, 2009 9:28 pm
by phat-customs
Running 31-10.5x15's on 7" rims on a shorty pajero (1st gen) and wondering what pressure's to run in the tyre??? the standard placard says 26 for the cheese-cutters it came with factory, when I got the car it was runnin massive pressures (read 38).

I ran 26 for a while but noticed that the tyre doesnt sit on the road properly, only the center of the tyre touches. The tyres are wearing very thin in the middle and heaps of tread on the outer lugs. SO i dropped it to 22 and the tyre seeeems to be sitting on the road better but im worried that its too low and will wear the outer edges...

whats peoples thoughts???

Posted: Thu Sep 10, 2009 9:37 pm
by -Scott-
I think something's wrong with your pressure gauge.

I had 31x10.5R15LTs on my Gen 2, and reckon 36psi was about right for highway driving (with typical loads.)

Have you tried the 4psi rule? Set pressures when the tyres are cold (i.e. first thing in the morning) & check them after an hour or so at highway speeds. If the pressure has increased 4psi, your cold pressure was about right. That's how I arrived at 36psi, and i got pretty even wear at that pressure. (These days, with 285/75R16, I still use the same pressure.)

But other factors may affect the "correct" pressure, such as vehicle weight (heavily loaded or stripped bare?) and tyre construction (passenger, or light truck?)

Do you own your own pressure gauge? Many years ago, driving mum's 1972 LJ Torana, I typically ran tyres at 26psi. One day, checking at the servo, they were all REAL low - and they took a LONG time to inflate.

Back on the road, the steering was REAL light - so I called in at the next servo, to find all my tyres were at 70psi. :shock:

So - there's many variables involved in determining the correct tyre pressure for a vehicle. Start sorting them out.

Posted: Thu Sep 10, 2009 10:43 pm
by grimbo
So when you searched did you read about the 4 psi rule? If not read about it because it really is the best way to ensure the pressure is right for you, your vehicle and your driving conditions

Posted: Thu Sep 10, 2009 10:52 pm
by zagan
I have the same (sort of) size tyre and was running at 40psi currently at 38psi, I think 40psi is better.

The tyres would get the tread chewed out of them at 36psi or less also too bouncy for my liking.

Posted: Thu Sep 10, 2009 11:40 pm
by alien
anyone know if the 4psi rule works with a zuk running big rubber? being that theres next to no weight on the tyre that is...

Posted: Fri Sep 11, 2009 8:35 am
by grimbo
Try it and see

Posted: Fri Sep 11, 2009 9:12 am
by alien
will do... dont know if i have anywhere to drive an hour for but ill see how i go...

I used the old talc-powder trick on my current tyres to determine 20psi as a good pressure (talc on the ground and roll over it to check contact with road).

Re: What Pressure??? (and yes i did search)

Posted: Fri Sep 11, 2009 11:10 am
by bazzle
phat-customs wrote:Running 31-10.5x15's on 7" rims on a shorty pajero (1st gen) and wondering what pressure's to run in the tyre??? the standard placard says 26 for the cheese-cutters it came with factory, when I got the car it was runnin massive pressures (read 38).

I ran 26 for a while but noticed that the tyre doesnt sit on the road properly, only the center of the tyre touches. The tyres are wearing very thin in the middle and heaps of tread on the outer lugs. SO i dropped it to 22 and the tyre seeeems to be sitting on the road better but im worried that its too low and will wear the outer edges...

whats peoples thoughts???
32psi (using a correct gauge)

Bazzle